CVE-2026-52906 (GCVE-0-2026-52906)

Vulnerability from cvelistv5 – Published: 2026-06-09 12:36 – Updated: 2026-06-14 18:09
VLAI
Title
9p: fix access mode flags being ORed instead of replaced
Summary
In the Linux kernel, the following vulnerability has been resolved: 9p: fix access mode flags being ORed instead of replaced Since commit 1f3e4142c0eb ("9p: convert to the new mount API"), v9fs_apply_options() applies parsed mount flags with |= onto flags already set by v9fs_session_init(). For 9P2000.L, session_init sets V9FS_ACCESS_CLIENT as the default, so when the user mounts with "access=user", both bits end up set. Access mode checks compare against exact values, so having both bits set matches neither mode. This causes v9fs_fid_lookup() to fall through to the default switch case, using INVALID_UID (nobody/65534) instead of current_fsuid() for all fid lookups. Root is then unable to chown or perform other privileged operations. Fix by clearing the access mask before applying the user's choice.
Severity
7.7 (High)
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 1f3e4142c0eb178089ea0cbc97506a061470ad27 , < b8f037e87a083291190204b959cda417aaf01058 (git)
Affected: 1f3e4142c0eb178089ea0cbc97506a061470ad27 , < da2346a48a5a1fed86c3fe3d73c0b60e7b3027c9 (git)
Create a notification for this product.
Linux Linux Affected: 6.19
Unaffected: 0 , < 6.19 (semver)
Unaffected: 7.0.4 , ≤ 7.0.* (semver)
Unaffected: 7.1 , ≤ * (original_commit_for_fix)
Create a notification for this product.
Show details on NVD website
To clipboard 

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/9p/v9fs.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "b8f037e87a083291190204b959cda417aaf01058",
              "status": "affected",
              "version": "1f3e4142c0eb178089ea0cbc97506a061470ad27",
              "versionType": "git"
            },
            {
              "lessThan": "da2346a48a5a1fed86c3fe3d73c0b60e7b3027c9",
              "status": "affected",
              "version": "1f3e4142c0eb178089ea0cbc97506a061470ad27",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/9p/v9fs.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.19"
            },
            {
              "lessThan": "6.19",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.0.*",
              "status": "unaffected",
              "version": "7.0.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.0.4",
                  "versionStartIncluding": "6.19",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1",
                  "versionStartIncluding": "6.19",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\n9p: fix access mode flags being ORed instead of replaced\n\nSince commit 1f3e4142c0eb (\"9p: convert to the new mount API\"),\nv9fs_apply_options() applies parsed mount flags with |= onto flags\nalready set by v9fs_session_init(). For 9P2000.L, session_init sets\nV9FS_ACCESS_CLIENT as the default, so when the user mounts with\n\"access=user\", both bits end up set. Access mode checks compare\nagainst exact values, so having both bits set matches neither mode.\n\nThis causes v9fs_fid_lookup() to fall through to the default switch\ncase, using INVALID_UID (nobody/65534) instead of current_fsuid()\nfor all fid lookups. Root is then unable to chown or perform other\nprivileged operations.\n\nFix by clearing the access mask before applying the user\u0027s choice."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.7,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N",
            "version": "3.1"
          }
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-06-14T18:09:41.521Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/b8f037e87a083291190204b959cda417aaf01058"
        },
        {
          "url": "https://git.kernel.org/stable/c/da2346a48a5a1fed86c3fe3d73c0b60e7b3027c9"
        }
      ],
      "title": "9p: fix access mode flags being ORed instead of replaced",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-52906",
    "datePublished": "2026-06-09T12:36:03.521Z",
    "dateReserved": "2026-06-09T07:44:35.366Z",
    "dateUpdated": "2026-06-14T18:09:41.521Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-52906",
      "date": "2026-06-23",
      "epss": "0.00121",
      "percentile": "0.02182"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-52906\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-06-09T14:16:45.047\",\"lastModified\":\"2026-06-14T06:16:25.727\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\n9p: fix access mode flags being ORed instead of replaced\\n\\nSince commit 1f3e4142c0eb (\\\"9p: convert to the new mount API\\\"),\\nv9fs_apply_options() applies parsed mount flags with |= onto flags\\nalready set by v9fs_session_init(). For 9P2000.L, session_init sets\\nV9FS_ACCESS_CLIENT as the default, so when the user mounts with\\n\\\"access=user\\\", both bits end up set. Access mode checks compare\\nagainst exact values, so having both bits set matches neither mode.\\n\\nThis causes v9fs_fid_lookup() to fall through to the default switch\\ncase, using INVALID_UID (nobody/65534) instead of current_fsuid()\\nfor all fid lookups. Root is then unable to chown or perform other\\nprivileged operations.\\n\\nFix by clearing the access mask before applying the user\u0027s choice.\"}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N\",\"baseScore\":7.7,\"baseSeverity\":\"HIGH\",\"attackVector\":\"LOCAL\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"NONE\"},\"exploitabilityScore\":2.5,\"impactScore\":5.2}]},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/b8f037e87a083291190204b959cda417aaf01058\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/da2346a48a5a1fed86c3fe3d73c0b60e7b3027c9\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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.