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GHSA-M6P4-6VJR-QQ2H

Vulnerability from github – Published: 2026-09-11 21:31 – Updated: 2026-09-13 09:32

Details

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

cifs: use cifs_invalidate_cache() in cifs_do_truncate() for O_TRUNC

cifs_do_truncate() is invoked from cifs_open() without i_rwsem, so it cannot use cifs_resize_file_locked() to perform a proper fscache cookie resize. Instead, add cifs_invalidate_cache() after cifs_setsize().

cifs_invalidate_cache() calls fscache_invalidate(), which works without holding i_rwsem: it unconditionally increments inval_counter and sets FSCACHE_COOKIE_NO_DATA_TO_READ, ensuring that stale cached data is not served once the cookie is later activated by fscache_use_cookie(). Truncation to zero leaves no valid cached data, making invalidation the correct semantic here.

Severity

7.1 (High)


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

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{
  "affected": [],
  "aliases": [
    "CVE-2026-89639"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-09-11T20:19:49Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\ncifs: use cifs_invalidate_cache() in cifs_do_truncate() for O_TRUNC\n\ncifs_do_truncate() is invoked from cifs_open() without i_rwsem, so it\ncannot use cifs_resize_file_locked() to perform a proper fscache cookie\nresize.  Instead, add cifs_invalidate_cache() after cifs_setsize().\n\ncifs_invalidate_cache() calls fscache_invalidate(), which works without\nholding i_rwsem: it unconditionally increments inval_counter and sets\nFSCACHE_COOKIE_NO_DATA_TO_READ, ensuring that stale cached data is not\nserved once the cookie is later activated by fscache_use_cookie().\nTruncation to zero leaves no valid cached data, making invalidation the\ncorrect semantic here.",
  "id": "GHSA-m6p4-6vjr-qq2h",
  "modified": "2026-09-13T09:32:26Z",
  "published": "2026-09-11T21:31:34Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-89639"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/364b183230586a62660a7280c1eb20138338eeb5"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/81fc3868a7f726980ff845c1d0d271051e5f0f45"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8b9b10fe5b8b492b27b9f4546742ea541a650213"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-89639 (GCVE-0-2026-89639)

Vulnerability from cvelistv5 – Published: 2026-09-11 19:45 – Updated: 2026-09-13 06:32

Title

cifs: use cifs_invalidate_cache() in cifs_do_truncate() for O_TRUNC

Summary

In the Linux kernel, the following vulnerability has been resolved: cifs: use cifs_invalidate_cache() in cifs_do_truncate() for O_TRUNC cifs_do_truncate() is invoked from cifs_open() without i_rwsem, so it cannot use cifs_resize_file_locked() to perform a proper fscache cookie resize. Instead, add cifs_invalidate_cache() after cifs_setsize(). cifs_invalidate_cache() calls fscache_invalidate(), which works without holding i_rwsem: it unconditionally increments inval_counter and sets FSCACHE_COOKIE_NO_DATA_TO_READ, ensuring that stale cached data is not served once the cookie is later activated by fscache_use_cookie(). Truncation to zero leaves no valid cached data, making invalidation the correct semantic here.

Severity

7.1 (High)


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

Assigner

Linux mitre root

References

3 references

URL	Tags
https://git.kernel.org/stable/c/8b9b10fe5b8b492b2…
https://git.kernel.org/stable/c/81fc3868a7f726980…
https://git.kernel.org/stable/c/364b183230586a626…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: efbcecdecefc26fa062c0e8210533ccad7d6bd4a , < 8b9b10fe5b8b492b27b9f4546742ea541a650213 (git) Affected: fa724e235cfdb0fb0bb427d0f9dfe864ae27403e , < 81fc3868a7f726980ff845c1d0d271051e5f0f45 (git) Affected: fa724e235cfdb0fb0bb427d0f9dfe864ae27403e , < 364b183230586a62660a7280c1eb20138338eeb5 (git) Affected: 6838bcac954487cc0a3c8a4ee1b3a3a30e244dc9 (git) Affected: 75640976cf474eb41682a13f2dbe9534ac26ca50 (git) Affected: 3513f3931c579ba2a715784c6dedc59e0d9282ee (git) Affected: 6.18.44 , < 6.18.50 (semver) Affected: 6.12.105 , < 6.13 (semver) Affected: 7.1.8 , < 7.2 (semver)
Linux	Linux	Affected: 7.2 Unaffected: 0 , < 7.2 (semver) Unaffected: 6.18.50 , ≤ 6.18.* (semver) Unaffected: 7.2.4 , ≤ 7.2.* (semver) Unaffected: 7.3-rc1 , ≤ * (original_commit_for_fix)

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/client/file.c"
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              "status": "affected",
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              "status": "unaffected",
              "version": "7.2.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
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              "versionType": "original_commit_for_fix"
            }
          ]
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      "cpeApplicability": [
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          "nodes": [
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              "cpeMatch": [
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              "negate": false,
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ncifs: use cifs_invalidate_cache() in cifs_do_truncate() for O_TRUNC\n\ncifs_do_truncate() is invoked from cifs_open() without i_rwsem, so it\ncannot use cifs_resize_file_locked() to perform a proper fscache cookie\nresize.  Instead, add cifs_invalidate_cache() after cifs_setsize().\n\ncifs_invalidate_cache() calls fscache_invalidate(), which works without\nholding i_rwsem: it unconditionally increments inval_counter and sets\nFSCACHE_COOKIE_NO_DATA_TO_READ, ensuring that stale cached data is not\nserved once the cookie is later activated by fscache_use_cookie().\nTruncation to zero leaves no valid cached data, making invalidation the\ncorrect semantic here."
        }
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            "version": "3.1"
          },
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              "value": "AV:L - cifs_do_truncate() runs from cifs_open() on the SMB client during a local open/openat with O_TRUNC on a mounted CIFS share (fs/smb/client/), not from ksmbd/nfsd or demux-thread packet parsing; a remote SMB peer cannot invoke this path.\nAC:L - A write-capable open with O_TRUNC deterministically skips fscache invalidation, then the same cifs_open() activates the cookie via fscache_use_cookie(); the attacker can also hold another fd so the cookie is already active, with no race or layout outside their control.\nPR:L - O_TRUNC requires only MAY_WRITE on the target inode, which an ordinary local user has on an already-mounted CIFS share; no init-namespace root, CAP_SYS_ADMIN, or user-namespace mount of CIFS is needed.\nUI:N - The attacker issues open(O_TRUNC) and follow-on reads/writes themselves; on common fstab/autofs/CIFS-home deployments with the fsc option already set, no other user must mount the share or open the file.\nS:U - Stale data stays within the local CIFS client\u0027s fscache and the same SMB file\u0027s contents; this is not a VM escape, IOMMU bypass, or other cross-authority boundary crossing.\nC:H - After O_TRUNC the cookie is activated without FSCACHE_COOKIE_NO_DATA_TO_READ, so later reads (including holes after a size-extending write) can return the full previously truncated file contents that should have been discarded.\nI:H - The same stale cookie presents discarded bytes as current file data and can persist them to the SMB server via netfs read-modify-write/writeback, fully replacing zeros or newly written contents on that file.\nA:N - The flaw is fscache coherency only; it does not oops, panic, deadlock, or exhaust kernel resources, so host availability is unaffected."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-13T06:32:19.311Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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        },
        {
          "url": "https://git.kernel.org/stable/c/364b183230586a62660a7280c1eb20138338eeb5"
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      ],
      "title": "cifs: use cifs_invalidate_cache() in cifs_do_truncate() for O_TRUNC",
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    "datePublished": "2026-09-11T19:45:32.532Z",
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    "dateUpdated": "2026-09-13T06:32:19.311Z",
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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.

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GHSA-M6P4-6VJR-QQ2H

CVE-2026-89639 (GCVE-0-2026-89639)

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Nomenclature