Vulnerability-Lookup

GHSA-6PC4-H32V-99RG

Vulnerability from github – Published: 2026-07-19 18:31 – Updated: 2026-07-20 15:31

Details

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

memfd: deny writeable mappings when implying SEAL_WRITE

When SEAL_EXEC is added, SEAL_WRITE is implied to make W^X. But the implied seal is set after the check that makes sure the memfd can not have any writable mappings. This means one can use SEAL_EXEC to apply SEAL_WRITE while having writeable mappings.

This breaks the contract that SEAL_WRITE provides and can be used by an attacker to pass a memfd that appears to be write sealed but can still be modified arbitrarily.

Fix this by adding the implied seals before the call for mapping_deny_writable() is done.

Severity

8.4 (High)


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

Show details on source website

JSON

To clipboard

{
  "affected": [],
  "aliases": [
    "CVE-2026-63952"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-362"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-07-19T16:17:13Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nmemfd: deny writeable mappings when implying SEAL_WRITE\n\nWhen SEAL_EXEC is added, SEAL_WRITE is implied to make W^X.  But the\nimplied seal is set after the check that makes sure the memfd can not have\nany writable mappings.  This means one can use SEAL_EXEC to apply\nSEAL_WRITE while having writeable mappings.\n\nThis breaks the contract that SEAL_WRITE provides and can be used by an\nattacker to pass a memfd that appears to be write sealed but can still be\nmodified arbitrarily.\n\nFix this by adding the implied seals before the call for\nmapping_deny_writable() is done.",
  "id": "GHSA-6pc4-h32v-99rg",
  "modified": "2026-07-20T15:31:53Z",
  "published": "2026-07-19T18:31:47Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-63952"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/0995d1f79aed8ccbf62056189dd53fd19726ea08"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3b041514cb6eae45869b020f743c14d983363222"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3be2a24f7f72ad7321ed6ad1715b956a4527bcf4"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/555702282d4536a865dfffb1cd4f6028f196e7e8"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b3f4f82d1315f1439059a83d1c22c51a5b43d99e"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-63952 (GCVE-0-2026-63952)

Vulnerability from cvelistv5 – Published: 2026-07-19 14:55 – Updated: 2026-10-19 20:17

Title

memfd: deny writeable mappings when implying SEAL_WRITE

Summary

In the Linux kernel, the following vulnerability has been resolved: memfd: deny writeable mappings when implying SEAL_WRITE When SEAL_EXEC is added, SEAL_WRITE is implied to make W^X. But the implied seal is set after the check that makes sure the memfd can not have any writable mappings. This means one can use SEAL_EXEC to apply SEAL_WRITE while having writeable mappings. This breaks the contract that SEAL_WRITE provides and can be used by an attacker to pass a memfd that appears to be write sealed but can still be modified arbitrarily. Fix this by adding the implied seals before the call for mapping_deny_writable() is done.

Severity

8.4 (High)


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

SSVC

Exploitation: none Automatable: no Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-10-16 15:34 UTC

CWE

CWE-362 - Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

Assigner

Linux CNA under the mitre root

CNA scorecard D 53/100 over 7033 records in the last 180 days details

References

5 references

URL	Tags
https://git.kernel.org/stable/c/b3f4f82d1315f1439…
https://git.kernel.org/stable/c/3be2a24f7f72ad732…
https://git.kernel.org/stable/c/0995d1f79aed8ccbf…
https://git.kernel.org/stable/c/555702282d4536a86…
https://git.kernel.org/stable/c/3b041514cb6eae458…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: c4f75bc8bd6b3d62665e1f5400c419540edb5601 , < b3f4f82d1315f1439059a83d1c22c51a5b43d99e (git) Affected: c4f75bc8bd6b3d62665e1f5400c419540edb5601 , < 3be2a24f7f72ad7321ed6ad1715b956a4527bcf4 (git) Affected: c4f75bc8bd6b3d62665e1f5400c419540edb5601 , < 0995d1f79aed8ccbf62056189dd53fd19726ea08 (git) Affected: c4f75bc8bd6b3d62665e1f5400c419540edb5601 , < 555702282d4536a865dfffb1cd4f6028f196e7e8 (git) Affected: c4f75bc8bd6b3d62665e1f5400c419540edb5601 , < 3b041514cb6eae45869b020f743c14d983363222 (git)
Linux	Linux	Affected: 6.3 Unaffected: 0 , < 6.3 (semver) Unaffected: 6.6.143 , ≤ 6.6.* (semver) Unaffected: 6.12.93 , ≤ 6.12.* (semver) Unaffected: 6.18.35 , ≤ 6.18.* (semver) Unaffected: 7.0.12 , ≤ 7.0.* (semver) Unaffected: 7.1 , ≤ * (original_commit_for_fix)

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-63952",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "total"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-10-16T15:34:10.687690Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "problemTypes": [
          {
            "descriptions": [
              {
                "cweId": "CWE-362",
                "description": "CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization (\u0027Race Condition\u0027)",
                "lang": "en",
                "type": "CWE"
              }
            ]
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-10-19T20:17:59.011Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "mm/memfd.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "b3f4f82d1315f1439059a83d1c22c51a5b43d99e",
              "status": "affected",
              "version": "c4f75bc8bd6b3d62665e1f5400c419540edb5601",
              "versionType": "git"
            },
            {
              "lessThan": "3be2a24f7f72ad7321ed6ad1715b956a4527bcf4",
              "status": "affected",
              "version": "c4f75bc8bd6b3d62665e1f5400c419540edb5601",
              "versionType": "git"
            },
            {
              "lessThan": "0995d1f79aed8ccbf62056189dd53fd19726ea08",
              "status": "affected",
              "version": "c4f75bc8bd6b3d62665e1f5400c419540edb5601",
              "versionType": "git"
            },
            {
              "lessThan": "555702282d4536a865dfffb1cd4f6028f196e7e8",
              "status": "affected",
              "version": "c4f75bc8bd6b3d62665e1f5400c419540edb5601",
              "versionType": "git"
            },
            {
              "lessThan": "3b041514cb6eae45869b020f743c14d983363222",
              "status": "affected",
              "version": "c4f75bc8bd6b3d62665e1f5400c419540edb5601",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "mm/memfd.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.3"
            },
            {
              "lessThan": "6.3",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.143",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.93",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.35",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.0.*",
              "status": "unaffected",
              "version": "7.0.12",
              "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": "6.6.143",
                  "versionStartIncluding": "6.3",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.93",
                  "versionStartIncluding": "6.3",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.35",
                  "versionStartIncluding": "6.3",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.0.12",
                  "versionStartIncluding": "6.3",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1",
                  "versionStartIncluding": "6.3",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmemfd: deny writeable mappings when implying SEAL_WRITE\n\nWhen SEAL_EXEC is added, SEAL_WRITE is implied to make W^X.  But the\nimplied seal is set after the check that makes sure the memfd can not have\nany writable mappings.  This means one can use SEAL_EXEC to apply\nSEAL_WRITE while having writeable mappings.\n\nThis breaks the contract that SEAL_WRITE provides and can be used by an\nattacker to pass a memfd that appears to be write sealed but can still be\nmodified arbitrarily.\n\nFix this by adding the implied seals before the call for\nmapping_deny_writable() is done."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 8.4,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - Exploitation requires local syscalls (memfd_create, mmap, fcntl) with no network-facing code path; the vulnerable logic is reached only through the local fcntl(F_ADD_SEALS) interface on a memfd file descriptor.\nAC:L - The attack is a reliable, deterministic syscall sequence (create executable memfd, establish a writable MAP_SHARED mapping, then apply F_SEAL_EXEC) with no race or attacker-uncontrollable conditions.\nPR:L - Any unprivileged local user can invoke memfd_create, mmap, and fcntl without capabilities; these interfaces are available inside unprivileged user namespaces with no real-root requirement.\nUI:N - Exploitation does not require a human victim action; in the highest-impact scenario a sandboxed process programmatically passes the sealed-appearing memfd to a trusting peer via IPC (e.g., SCM_RIGHTS) without user interaction.\nS:C - The bug breaks the memfd seal security contract designed for mutually untrusted parties, allowing a malicious local peer to deceive a separate process that relies on F_SEAL_WRITE immutability, crossing the inter-process trust boundary (sandbox/W^X enforcement).\nC:H - Bypassing write-seal/W^X guarantees enables arbitrary modification of executable memfd contents presented as immutable, which can be leveraged for arbitrary code execution in a trusting victim process and thereby full read of that process\u0027s memory.\nI:H - The vulnerability allows arbitrary modification of memory that is advertised as write-sealed (F_SEAL_WRITE), defeating the kernel\u0027s immutability guarantee and enabling W^X bypass and code injection into trusted execution contexts.\nA:N - The flaw is a logic error in seal enforcement that does not cause kernel crashes, panics, hangs, or denial of service; exploitation maintains availability while subverting integrity guarantees."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:37:37.398Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/b3f4f82d1315f1439059a83d1c22c51a5b43d99e"
        },
        {
          "url": "https://git.kernel.org/stable/c/3be2a24f7f72ad7321ed6ad1715b956a4527bcf4"
        },
        {
          "url": "https://git.kernel.org/stable/c/0995d1f79aed8ccbf62056189dd53fd19726ea08"
        },
        {
          "url": "https://git.kernel.org/stable/c/555702282d4536a865dfffb1cd4f6028f196e7e8"
        },
        {
          "url": "https://git.kernel.org/stable/c/3b041514cb6eae45869b020f743c14d983363222"
        }
      ],
      "title": "memfd: deny writeable mappings when implying SEAL_WRITE",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-63952",
    "datePublished": "2026-07-19T14:55:44.809Z",
    "dateReserved": "2026-07-19T07:54:57.023Z",
    "dateUpdated": "2026-10-19T20:17:59.011Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

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.

Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

Order JSON

Publication & reservation Sightings KEV catalogs Other timestamps

Loading timeline…

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