Vulnerability-Lookup

ubuntu-cve-2026-72854

Vulnerability from osv_ubuntu

Published

2026-08-21 00:00

Modified

2026-08-24 07:41

Summary

Details

(msgpack_unpacker_expand_buffer in src/unpack.c, reached through the pu ...)

Severity

5.3 (Medium)


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

5.8 (Medium)


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

N/A (UNKNOWN)


                    
                      medium

References

URL

Type

	https://ubuntu.com/security/CVE-2026-72854	REPORT
	https://www.cve.org/CVERecord?id=CVE-2026-72854	REPORT

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libmsgpackc2",
            "binary_version": "2.1.5-1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:18.04:LTS",
        "name": "msgpack-c",
        "purl": "pkg:deb/ubuntu/msgpack-c@2.1.5-1?arch=source\u0026distro=bionic"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.1.5-1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libmsgpackc2",
            "binary_version": "3.0.1-3"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:20.04:LTS",
        "name": "msgpack-c",
        "purl": "pkg:deb/ubuntu/msgpack-c@3.0.1-3?arch=source\u0026distro=focal"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "3.0.1-3"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libmsgpackc2",
            "binary_version": "3.3.0-4"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:22.04:LTS",
        "name": "msgpack-c",
        "purl": "pkg:deb/ubuntu/msgpack-c@3.3.0-4?arch=source\u0026distro=jammy"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "3.3.0-4"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libmsgpackc2",
            "binary_version": "4.0.0-3build1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:24.04:LTS",
        "name": "msgpack-c",
        "purl": "pkg:deb/ubuntu/msgpack-c@4.0.0-3build1?arch=source\u0026distro=noble"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "4.0.0-3",
        "4.0.0-3build1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libmsgpack-c2",
            "binary_version": "6.1.0-2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:26.04:LTS",
        "name": "msgpack-c",
        "purl": "pkg:deb/ubuntu/msgpack-c@6.1.0-2?arch=source\u0026distro=resolute"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "6.0.1-3",
        "6.1.0-2"
      ]
    }
  ],
  "aliases": [],
  "details": "(msgpack_unpacker_expand_buffer in src/unpack.c, reached through the pu ...)",
  "id": "UBUNTU-CVE-2026-72854",
  "modified": "2026-08-24T07:41:36Z",
  "published": "2026-08-21T00:00:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-72854"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-72854"
    }
  ],
  "related": [],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:L",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:4.0/AV:L/AC:H/AT:P/PR:N/UI:P/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2026-72854"
  ]
}

CVE-2026-72854 (GCVE-0-2026-72854)

Vulnerability from cvelistv5 – Published: 2026-08-20 18:19 – Updated: 2026-08-20 18:53

Title

msgpack-c Integer Overflow in msgpack_unpacker_expand_buffer Causes a False-Success Undersized Reservation

Summary

msgpack_unpacker_expand_buffer in src/unpack.c, reached through the public msgpack_unpacker_reserve_buffer API, computes its new buffer size using an unchecked size_t addition of the requested size and the amount already used. The doubling loop guards its own multiplication against overflow, but the addition in the loop condition is unguarded, so a request near SIZE_MAX wraps: the loop condition is already satisfied, the allocation is performed at the small pre-wrap size, and the function returns true. The caller is told the requested capacity was reserved when it was not, so a subsequent write of the requested length overflows the heap buffer. The library's own example/lib_buffer_unpack.c demonstrates the reserve-then-write pattern, and its defensive assert comparing capacity against the request is compiled out under NDEBUG. msgpack-c's own decode entry points do not derive the reservation size from untrusted input, so reaching this requires an integration that passes an attacker-influenced length to the reservation API, such as a length-prefixed streaming transport.

Severity

5.3 (Medium)


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

5.8 (Medium)


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

SSVC

Exploitation: poc Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-20 18:52 UTC

CWE

CWE-190 - Integer Overflow or Wraparound
CWE-787 - Out-of-bounds Write

Assigner

VulnCheck mitre root

References

6 references

URL	Tags
https://github.com/msgpack/msgpack-c/issues/1181	issue-tracking
https://github.com/msgpack/msgpack-c/blob/c-7.0.1…	technical-description
https://github.com/msgpack/msgpack-c/blob/c-7.0.1…	technical-description
https://github.com/msgpack/msgpack-c/blob/c-7.0.1…	technical-description
https://github.com/msgpack/msgpack-c	product
https://www.vulncheck.com/advisories/msgpack-c-in…	third-party-advisory

Impacted products

1 product

Vendor	Product	Version
msgpack	msgpack-c	Affected: 0 , ≤ 7.0.1 (custom)

Date Public

2026-08-13 00:00

Credits

mtholmquist

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-72854",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-08-20T18:52:52.984726Z",
                "version": "2.0.3"
              },
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        "providerMetadata": {
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          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
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          {
            "tags": [
              "exploit"
            ],
            "url": "https://github.com/msgpack/msgpack-c/issues/1181"
          }
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        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "msgpack-c",
          "repo": "https://github.com/msgpack/msgpack-c",
          "vendor": "msgpack",
          "versions": [
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              "status": "affected",
              "version": "0",
              "versionType": "custom"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "reporter",
          "value": "mtholmquist"
        }
      ],
      "datePublic": "2026-08-13T00:00:00.000Z",
      "descriptions": [
        {
          "lang": "en",
          "value": "msgpack_unpacker_expand_buffer in src/unpack.c, reached through the public msgpack_unpacker_reserve_buffer API, computes its new buffer size using an unchecked size_t addition of the requested size and the amount already used. The doubling loop guards its own multiplication against overflow, but the addition in the loop condition is unguarded, so a request near SIZE_MAX wraps: the loop condition is already satisfied, the allocation is performed at the small pre-wrap size, and the function returns true. The caller is told the requested capacity was reserved when it was not, so a subsequent write of the requested length overflows the heap buffer. The library\u0027s own example/lib_buffer_unpack.c demonstrates the reserve-then-write pattern, and its defensive assert comparing capacity against the request is compiled out under NDEBUG. msgpack-c\u0027s own decode entry points do not derive the reservation size from untrusted input, so reaching this requires an integration that passes an attacker-influenced length to the reservation API, such as a length-prefixed streaming transport."
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      ],
      "metrics": [
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            "attackComplexity": "HIGH",
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            "availabilityImpact": "LOW",
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      "title": "msgpack-c Integer Overflow in msgpack_unpacker_expand_buffer Causes a False-Success Undersized Reservation",
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    "datePublished": "2026-08-20T18:19:24.266Z",
    "dateReserved": "2026-08-10T15:16:31.371Z",
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}

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.

Action not permitted

ubuntu-cve-2026-72854

Vulnerability from osv_ubuntu

CVE-2026-72854 (GCVE-0-2026-72854)

Tags

Sightings

Nomenclature