Vulnerability-Lookup

CVE-2026-90042 (GCVE-0-2026-90042)

Vulnerability from cvelistv5 – Published: 2026-09-16 10:33 – Updated: 2026-09-16 14:41

Title

ceph: properly decrypt filenames in vmalloc() buffers

Summary

In the Linux kernel, the following vulnerability has been resolved: ceph: properly decrypt filenames in vmalloc() buffers The fscrypt subsystem uses the scatterlist crypto API, inheriting its requirement that any buffers are in the linear mapping region. However, the messenger client uses kvmalloc() to create buffers for messages, which will occasionally place those buffers in the vmalloc() region when physical memory fragmentation doesn't permit a large enough kmalloc(). The various callers of ceph_fname_to_usr() directly pass (slices of) raw messages from the MDS without considering that the messages may be in vmalloc() buffers, resulting in oopses especially on non-x86 platforms (see 'Closes:' for more details and a reproducer). Make ceph_fname_to_usr() explicitly tolerant of vmalloc()-allocated fname->ctext, fname->name, and/or oname->name buffers, using `tname` (which, when non-null, must be a linear address; when null, is briefly allocated as necessary) as a bounce buffer to avoid passing any inappropriate addresses to fscrypt_fname_disk_to_usr(). Additionally change parse_reply_info_readdir() -- the only function to supply its own `tname` -- to follow the new "tname must never come from vmalloc()" rule by passing NULL when the message is not in the linear region. Though this causes a per-dentry kmalloc()+kfree(), this overhead exists only when processing the minority of messages that spill into vmalloc(). My (crude) testing puts this at only about 1 in 8,000 readdir messages. Still, if the overhead proves unreasonable in the future, it is easy enough to mitigate: a future change could allocate a bounce buffer in parse_reply_info_readdir() and use that as `tname` instead.

Severity

9.8 (Critical)


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

Assigner

Linux mitre root

References

3 references

URL	Tags
https://git.kernel.org/stable/c/110747ff535e3d98a…
https://git.kernel.org/stable/c/3b467c68803d7c7e8…
https://git.kernel.org/stable/c/e939fc6a7bd969a58…

Impacted products

2 products

Vendor	Product	Version	CPE status
Linux	Linux	Affected: 457117f077c6749d1e28469eae91fb69c9806768 , < 110747ff535e3d98ac17d68dbd056bb6ef000e23 (git) Affected: 457117f077c6749d1e28469eae91fb69c9806768 , < 3b467c68803d7c7e82678289e598afd44faa6101 (git) Affected: 457117f077c6749d1e28469eae91fb69c9806768 , < e939fc6a7bd969a58a150b7f188c1047138403e3 (git)	guessed
Linux	Linux	Affected: 6.6 Unaffected: 0 , < 6.6 (semver) Unaffected: 6.18.51 , ≤ 6.18.* (semver) Unaffected: 7.2.5 , ≤ 7.2.* (semver) Unaffected: 7.3-rc1 , ≤ * (original_commit_for_fix)	guessed

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/ceph/crypto.c",
            "fs/ceph/mds_client.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "110747ff535e3d98ac17d68dbd056bb6ef000e23",
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              "version": "457117f077c6749d1e28469eae91fb69c9806768",
              "versionType": "git"
            },
            {
              "lessThan": "3b467c68803d7c7e82678289e598afd44faa6101",
              "status": "affected",
              "version": "457117f077c6749d1e28469eae91fb69c9806768",
              "versionType": "git"
            },
            {
              "lessThan": "e939fc6a7bd969a58a150b7f188c1047138403e3",
              "status": "affected",
              "version": "457117f077c6749d1e28469eae91fb69c9806768",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/ceph/crypto.c",
            "fs/ceph/mds_client.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.6"
            },
            {
              "lessThan": "6.6",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.51",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.5",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.51",
                  "versionStartIncluding": "6.6",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.5",
                  "versionStartIncluding": "6.6",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3-rc1",
                  "versionStartIncluding": "6.6",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nceph: properly decrypt filenames in vmalloc() buffers\n\nThe fscrypt subsystem uses the scatterlist crypto API, inheriting its\nrequirement that any buffers are in the linear mapping region. However,\nthe messenger client uses kvmalloc() to create buffers for messages,\nwhich will occasionally place those buffers in the vmalloc() region when\nphysical memory fragmentation doesn\u0027t permit a large enough kmalloc().\nThe various callers of ceph_fname_to_usr() directly pass (slices of) raw\nmessages from the MDS without considering that the messages may be in\nvmalloc() buffers, resulting in oopses especially on non-x86 platforms\n(see \u0027Closes:\u0027 for more details and a reproducer).\n\nMake ceph_fname_to_usr() explicitly tolerant of vmalloc()-allocated\nfname-\u003ectext, fname-\u003ename, and/or oname-\u003ename buffers, using `tname`\n(which, when non-null, must be a linear address; when null, is briefly\nallocated as necessary) as a bounce buffer to avoid passing any\ninappropriate addresses to fscrypt_fname_disk_to_usr().\n\nAdditionally change parse_reply_info_readdir() -- the only function to\nsupply its own `tname` -- to follow the new \"tname must never come from\nvmalloc()\" rule by passing NULL when the message is not in the linear\nregion. Though this causes a per-dentry kmalloc()+kfree(), this overhead\nexists only when processing the minority of messages that spill into\nvmalloc(). My (crude) testing puts this at only about 1 in 8,000 readdir\nmessages. Still, if the overhead proves unreasonable in the future, it\nis easy enough to mitigate: a future change could allocate a bounce\nbuffer in parse_reply_info_readdir() and use that as `tname` instead."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 9.8,
            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - ceph_fname_to_usr() runs while parsing CEPH_MSG_CLIENT_REPLY on the kernel CephFS client TCP session (mds_dispatch \u2192 handle_reply \u2192 parse_reply_info_readdir/fill_trace); a malicious or compromised MDS delivers the kvmalloc\u0027d filename buffers that are passed into fscrypt.\nAC:L - The MDS fully controls hdr.front_len (up to CEPH_MSG_MAX_FRONT_LEN, 16MB). kvmalloc() of that size skips costly kmalloc reclaim and falls back to vmalloc deterministically, so sg_init_one() on the message names does not depend on incidental fragmentation or a race.\nPR:N - The attacker is the remote MDS peer on an already-connected kernel CephFS client and needs no Linux UID, capability, or init-namespace root on the victim, matching other MDS-driven client CVEs such as CVE-2026-89651.\nUI:N - Once encrypted CephFS is mounted with keys loaded (standard in Rook/Kubernetes/OpenStack, including NFS re-export LOOKUPNAME), readdir and lookup replies are processed automatically in the ceph-msgr path with no further victim mount or interactive step at exploit time.\nS:U - Wrong-page scatterlist crypto and any resulting kernel memory corruption stay inside the victim host\u0027s CephFS client and do not cross a VM, IOMMU, or sandbox security boundary.\nC:H - fname_decrypt() builds src_sg with sg_set_buf()/virt_to_page() on the vmalloc MDS buffer, so skcipher decryption reads unintended kernel pages as ciphertext; that memory-corruption read is High per kernel UAF/wrong-page guidance.\nI:H - parse_reply_info_readdir() decrypts filenames in place, so dst_sg also aliases the vmalloc message; crypto_skcipher_decrypt() then writes plaintext through virt_to_page() of a non-linear address, a wrong-page kernel write scored High.\nA:H - Passing vmalloc addresses into the scatterlist crypto API oopses or panics, especially on non-x86 where virt_to_page() of a non-linear address faults in scatterwalk, and a malicious MDS can repeat this on every encrypted readdir reply."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-16T14:41:54.935Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
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          "url": "https://git.kernel.org/stable/c/110747ff535e3d98ac17d68dbd056bb6ef000e23"
        },
        {
          "url": "https://git.kernel.org/stable/c/3b467c68803d7c7e82678289e598afd44faa6101"
        },
        {
          "url": "https://git.kernel.org/stable/c/e939fc6a7bd969a58a150b7f188c1047138403e3"
        }
      ],
      "title": "ceph: properly decrypt filenames in vmalloc() buffers",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-90042",
    "datePublished": "2026-09-16T10:33:40.210Z",
    "dateReserved": "2026-09-11T19:38:34.783Z",
    "dateUpdated": "2026-09-16T14:41:54.935Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-90042\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-09-16T11:17:17.450\",\"lastModified\":\"2026-09-16T15:18:26.873\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nceph: properly decrypt filenames in vmalloc() buffers\\n\\nThe fscrypt subsystem uses the scatterlist crypto API, inheriting its\\nrequirement that any buffers are in the linear mapping region. However,\\nthe messenger client uses kvmalloc() to create buffers for messages,\\nwhich will occasionally place those buffers in the vmalloc() region when\\nphysical memory fragmentation doesn\u0027t permit a large enough kmalloc().\\nThe various callers of ceph_fname_to_usr() directly pass (slices of) raw\\nmessages from the MDS without considering that the messages may be in\\nvmalloc() buffers, resulting in oopses especially on non-x86 platforms\\n(see \u0027Closes:\u0027 for more details and a reproducer).\\n\\nMake ceph_fname_to_usr() explicitly tolerant of vmalloc()-allocated\\nfname-\u003ectext, fname-\u003ename, and/or oname-\u003ename buffers, using `tname`\\n(which, when non-null, must be a linear address; when null, is briefly\\nallocated as necessary) as a bounce buffer to avoid passing any\\ninappropriate addresses to fscrypt_fname_disk_to_usr().\\n\\nAdditionally change parse_reply_info_readdir() -- the only function to\\nsupply its own `tname` -- to follow the new \\\"tname must never come from\\nvmalloc()\\\" rule by passing NULL when the message is not in the linear\\nregion. Though this causes a per-dentry kmalloc()+kfree(), this overhead\\nexists only when processing the minority of messages that spill into\\nvmalloc(). My (crude) testing puts this at only about 1 in 8,000 readdir\\nmessages. Still, if the overhead proves unreasonable in the future, it\\nis easy enough to mitigate: a future change could allocate a bounce\\nbuffer in parse_reply_info_readdir() and use that as `tname` instead.\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"fs/ceph/crypto.c\",\"fs/ceph/mds_client.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"457117f077c6749d1e28469eae91fb69c9806768\",\"lessThan\":\"110747ff535e3d98ac17d68dbd056bb6ef000e23\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"457117f077c6749d1e28469eae91fb69c9806768\",\"lessThan\":\"3b467c68803d7c7e82678289e598afd44faa6101\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"457117f077c6749d1e28469eae91fb69c9806768\",\"lessThan\":\"e939fc6a7bd969a58a150b7f188c1047138403e3\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"fs/ceph/crypto.c\",\"fs/ceph/mds_client.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"6.6\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"6.6\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.18.51\",\"lessThanOrEqual\":\"6.18.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.2.5\",\"lessThanOrEqual\":\"7.2.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.3-rc1\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H\",\"baseScore\":9.8,\"baseSeverity\":\"CRITICAL\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":3.9,\"impactScore\":5.9}]},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/110747ff535e3d98ac17d68dbd056bb6ef000e23\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/3b467c68803d7c7e82678289e598afd44faa6101\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/e939fc6a7bd969a58a150b7f188c1047138403e3\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}

FKIE_CVE-2026-90042

Vulnerability from fkie_nvd - Published: 2026-09-16 11:17 - Updated: 2026-09-16 15:18

Severity

9.8 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Summary

References

	URL	Tags
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/110747ff535e3d98ac17d68dbd056bb6ef000e23
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/3b467c68803d7c7e82678289e598afd44faa6101
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/e939fc6a7bd969a58a150b7f188c1047138403e3

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/ceph/crypto.c",
            "fs/ceph/mds_client.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "110747ff535e3d98ac17d68dbd056bb6ef000e23",
              "status": "affected",
              "version": "457117f077c6749d1e28469eae91fb69c9806768",
              "versionType": "git"
            },
            {
              "lessThan": "3b467c68803d7c7e82678289e598afd44faa6101",
              "status": "affected",
              "version": "457117f077c6749d1e28469eae91fb69c9806768",
              "versionType": "git"
            },
            {
              "lessThan": "e939fc6a7bd969a58a150b7f188c1047138403e3",
              "status": "affected",
              "version": "457117f077c6749d1e28469eae91fb69c9806768",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/ceph/crypto.c",
            "fs/ceph/mds_client.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.6"
            },
            {
              "lessThan": "6.6",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.51",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.5",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nceph: properly decrypt filenames in vmalloc() buffers\n\nThe fscrypt subsystem uses the scatterlist crypto API, inheriting its\nrequirement that any buffers are in the linear mapping region. However,\nthe messenger client uses kvmalloc() to create buffers for messages,\nwhich will occasionally place those buffers in the vmalloc() region when\nphysical memory fragmentation doesn\u0027t permit a large enough kmalloc().\nThe various callers of ceph_fname_to_usr() directly pass (slices of) raw\nmessages from the MDS without considering that the messages may be in\nvmalloc() buffers, resulting in oopses especially on non-x86 platforms\n(see \u0027Closes:\u0027 for more details and a reproducer).\n\nMake ceph_fname_to_usr() explicitly tolerant of vmalloc()-allocated\nfname-\u003ectext, fname-\u003ename, and/or oname-\u003ename buffers, using `tname`\n(which, when non-null, must be a linear address; when null, is briefly\nallocated as necessary) as a bounce buffer to avoid passing any\ninappropriate addresses to fscrypt_fname_disk_to_usr().\n\nAdditionally change parse_reply_info_readdir() -- the only function to\nsupply its own `tname` -- to follow the new \"tname must never come from\nvmalloc()\" rule by passing NULL when the message is not in the linear\nregion. Though this causes a per-dentry kmalloc()+kfree(), this overhead\nexists only when processing the minority of messages that spill into\nvmalloc(). My (crude) testing puts this at only about 1 in 8,000 readdir\nmessages. Still, if the overhead proves unreasonable in the future, it\nis easy enough to mitigate: a future change could allocate a bounce\nbuffer in parse_reply_info_readdir() and use that as `tname` instead."
    }
  ],
  "id": "CVE-2026-90042",
  "lastModified": "2026-09-16T15:18:26.873",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 9.8,
          "baseSeverity": "CRITICAL",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 5.9,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-09-16T11:17:17.450",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/110747ff535e3d98ac17d68dbd056bb6ef000e23"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/3b467c68803d7c7e82678289e598afd44faa6101"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/e939fc6a7bd969a58a150b7f188c1047138403e3"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}

GHSA-39Q8-GJM7-PM22

Vulnerability from github – Published: 2026-09-16 12:30 – Updated: 2026-09-16 15:31

Details

In the Linux kernel, the following vulnerability has been resolved:

ceph: properly decrypt filenames in vmalloc() buffers

The fscrypt subsystem uses the scatterlist crypto API, inheriting its requirement that any buffers are in the linear mapping region. However, the messenger client uses kvmalloc() to create buffers for messages, which will occasionally place those buffers in the vmalloc() region when physical memory fragmentation doesn't permit a large enough kmalloc(). The various callers of ceph_fname_to_usr() directly pass (slices of) raw messages from the MDS without considering that the messages may be in vmalloc() buffers, resulting in oopses especially on non-x86 platforms (see 'Closes:' for more details and a reproducer).

Make ceph_fname_to_usr() explicitly tolerant of vmalloc()-allocated fname->ctext, fname->name, and/or oname->name buffers, using tname (which, when non-null, must be a linear address; when null, is briefly allocated as necessary) as a bounce buffer to avoid passing any inappropriate addresses to fscrypt_fname_disk_to_usr().

Additionally change parse_reply_info_readdir() -- the only function to supply its own tname -- to follow the new "tname must never come from vmalloc()" rule by passing NULL when the message is not in the linear region. Though this causes a per-dentry kmalloc()+kfree(), this overhead exists only when processing the minority of messages that spill into vmalloc(). My (crude) testing puts this at only about 1 in 8,000 readdir messages. Still, if the overhead proves unreasonable in the future, it is easy enough to mitigate: a future change could allocate a bounce buffer in parse_reply_info_readdir() and use that as tname instead.

Severity

9.8 (Critical)


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

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{
  "affected": [],
  "aliases": [
    "CVE-2026-90042"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-09-16T11:17:17Z",
    "severity": "CRITICAL"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nceph: properly decrypt filenames in vmalloc() buffers\n\nThe fscrypt subsystem uses the scatterlist crypto API, inheriting its\nrequirement that any buffers are in the linear mapping region. However,\nthe messenger client uses kvmalloc() to create buffers for messages,\nwhich will occasionally place those buffers in the vmalloc() region when\nphysical memory fragmentation doesn\u0027t permit a large enough kmalloc().\nThe various callers of ceph_fname_to_usr() directly pass (slices of) raw\nmessages from the MDS without considering that the messages may be in\nvmalloc() buffers, resulting in oopses especially on non-x86 platforms\n(see \u0027Closes:\u0027 for more details and a reproducer).\n\nMake ceph_fname_to_usr() explicitly tolerant of vmalloc()-allocated\nfname-\u003ectext, fname-\u003ename, and/or oname-\u003ename buffers, using `tname`\n(which, when non-null, must be a linear address; when null, is briefly\nallocated as necessary) as a bounce buffer to avoid passing any\ninappropriate addresses to fscrypt_fname_disk_to_usr().\n\nAdditionally change parse_reply_info_readdir() -- the only function to\nsupply its own `tname` -- to follow the new \"tname must never come from\nvmalloc()\" rule by passing NULL when the message is not in the linear\nregion. Though this causes a per-dentry kmalloc()+kfree(), this overhead\nexists only when processing the minority of messages that spill into\nvmalloc(). My (crude) testing puts this at only about 1 in 8,000 readdir\nmessages. Still, if the overhead proves unreasonable in the future, it\nis easy enough to mitigate: a future change could allocate a bounce\nbuffer in parse_reply_info_readdir() and use that as `tname` instead.",
  "id": "GHSA-39q8-gjm7-pm22",
  "modified": "2026-09-16T15:31:08Z",
  "published": "2026-09-16T12:30:46Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-90042"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/110747ff535e3d98ac17d68dbd056bb6ef000e23"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3b467c68803d7c7e82678289e598afd44faa6101"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e939fc6a7bd969a58a150b7f188c1047138403e3"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}

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.

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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-2026-90042 (GCVE-0-2026-90042)

FKIE_CVE-2026-90042

GHSA-39Q8-GJM7-PM22

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