CVE-2025-39964 (GCVE-0-2025-39964)

Vulnerability from cvelistv5 – Published: 2025-10-13 13:48 – Updated: 2026-09-19 03:56
VLAI CISA Previdian
Title
crypto: af_alg - Disallow concurrent writes in af_alg_sendmsg
Summary
In the Linux kernel, the following vulnerability has been resolved: crypto: af_alg - Disallow concurrent writes in af_alg_sendmsg Issuing two writes to the same af_alg socket is bogus as the data will be interleaved in an unpredictable fashion. Furthermore, concurrent writes may create inconsistencies in the internal socket state. Disallow this by adding a new ctx->write field that indiciates exclusive ownership for writing.
SSVC
Exploitation: active Automatable: no Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-18 00:00 UTC
CWE
  • CWE-362 - Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 , < 0f28c4adbc4a97437874c9b669fd7958a8c6d6ce (git)
Affected: 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 , < e4c1ec11132ec466f7362a95f36a506ce4dc08c9 (git)
Affected: 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 , < 1f323a48e9b5ebfe6dc7d130fdf5c3c0e92a07c8 (git)
Affected: 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 , < 7c4491b5644e3a3708f3dbd7591be0a570135b84 (git)
Affected: 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 , < 9aee87da5572b3a14075f501752e209801160d3d (git)
Affected: 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 , < 45bcf60fe49b37daab1acee57b27211ad1574042 (git)
Affected: 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 , < 1b34cbbf4f011a121ef7b2d7d6e6920a036d5285 (git)
guessed Create a notification for this product.
Linux Linux Affected: 2.6.38
Unaffected: 0 , < 2.6.38 (semver)
Unaffected: 5.10.245 , ≤ 5.10.* (semver)
Unaffected: 5.15.194 , ≤ 5.15.* (semver)
Unaffected: 6.1.154 , ≤ 6.1.* (semver)
Unaffected: 6.6.108 , ≤ 6.6.* (semver)
Unaffected: 6.12.49 , ≤ 6.12.* (semver)
Unaffected: 6.16.9 , ≤ 6.16.* (semver)
Unaffected: 6.17 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP Affected: V3.1.6 , < * (custom)
guessed Create a notification for this product.
Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP Affected: V3.1.6 , < * (custom)
guessed Create a notification for this product.
Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP Affected: V3.1.6 , < * (custom)
guessed Create a notification for this product.
CISA
Known Exploited Vulnerability - GCVE BCP-07 Compliant

Vulnerability ID: CVE-2025-39964

Status: Confirmed

Status Updated: 2026-09-18 00:00 UTC

Exploited: Yes


Timestamps
First Seen: 2026-09-18
Asserted: 2026-09-18

Scope
Notes: Linux Kernel Race Condition Vulnerability | Affected: Linux / Kernel | Description: Linux Kernel contains a race condition vulnerability which allows concurrent writes to the same AF_ALG socket causing data to be unpredictably interleaved and creating inconsistencies in the socket's internal state. | Required action: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines. | Due date: 2026-09-21 | Known ransomware campaign use (KEV): Unknown | Notes (KEV): This vulnerability affects an open-source component, third-party library, protocol, or proprietary implementation that could be used by different products. For more information, please see: ; https://git.kernel.org/stable/c/0f28c4adbc4a97437874c9b669fd7958a8c6d6ce; https://git.kernel.org/stable/c/e4c1ec11132ec466f7362a95f36a506ce4dc08c9; https://git.kernel.org/stable/c/1f323a48e9b5ebfe6dc7d130fdf5c3c0e92a07c8; https://git.kernel.org/stable/c/7c4491b5644e3a3708f3dbd7591be0a570135b84; https://git.kernel.org/stable/c/9aee87da5572b3a14075f501752e209801160d3d; https://git.kernel.org/stable/c/45bcf60fe49b37daab1acee57b27211ad1574042; https://git.kernel.org/stable/c/1b34cbbf4f011a121ef7b2d7d6e6920a036d5285 ; BOD 26-04: https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk ; Forensics Triage Requirements: https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk ; https://nvd.nist.gov/vuln/detail/CVE-2025-39964

Evidence

Type: Vendor Report

Signal: Successful Exploitation

Confidence: 80%

Source: cisa-kev


Details
Cwes CWE-362
Feed CISA Known Exploited Vulnerabilities Catalog
Product Kernel
Due Date 2026-09-21
Date Added 2026-09-18
Vendorproject Linux
Vulnerabilityname Linux Kernel Race Condition Vulnerability
Knownransomwarecampaignuse Unknown

References

Created: 2026-09-18 15:00 UTC | Updated: 2026-09-18 15:00 UTC
Previdian
Known Exploited Vulnerability - GCVE BCP-07 Compliant

Vulnerability ID: CVE-2025-39964

Status: Confirmed

Status Updated: 2026-09-18 14:30 UTC

Exploited: Yes


Timestamps
First Seen: 2026-09-18
Asserted: 2026-09-18

Scope
Notes: crypto: af_alg - Disallow concurrent writes in af_alg_sendmsg | Affected: Linux / Linux | CVSS: 7.8 (HIGH) | EPSS: 0.00323 | Used in malware: unknown | Not yet in CISA KEV: False

Evidence

Type: Public Report

Signal: Successful Exploitation

Confidence: 70%

Source: previdian


Details
Feed Previdian (previdian.com)
Title crypto: af_alg - Disallow concurrent writes in af_alg_sendmsg
Cve Id CVE-2025-39964
Vendor Linux
Ghsa Id GHSA-WR5G-MFHW-RPFJ
Product Linux
Added Date 2026-09-18T14:30:42.702Z
Cvss Score 7.8
Epss Score 0.00323
Previous Ids
Cvss Severity HIGH
Virtual Patch False
Cvss Estimated False
Epss Percentile 0.25599
Used In Malware unknown
Vulnerability Id CVE-2025-39964
Ahead Of Cisa Kev None
Not Yet In Cisa Kev False

References

Created: 2026-09-19 15:00 UTC | Updated: 2026-09-19 15:00 UTC
Show details on NVD website

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                  "version": "8ff590903d5fc7f5a0a988c38267a3d08e6393a2",
                  "versionType": "git"
                },
                {
                  "lessThan": "9aee87da5572b3a14075f501752e209801160d3d",
                  "status": "affected",
                  "version": "8ff590903d5fc7f5a0a988c38267a3d08e6393a2",
                  "versionType": "git"
                },
                {
                  "lessThan": "45bcf60fe49b37daab1acee57b27211ad1574042",
                  "status": "affected",
                  "version": "8ff590903d5fc7f5a0a988c38267a3d08e6393a2",
                  "versionType": "git"
                },
                {
                  "lessThan": "1b34cbbf4f011a121ef7b2d7d6e6920a036d5285",
                  "status": "affected",
                  "version": "8ff590903d5fc7f5a0a988c38267a3d08e6393a2",
                  "versionType": "git"
                }
              ]
            },
            {
              "defaultStatus": "affected",
              "product": "Linux",
              "programFiles": [
                "crypto/af_alg.c",
                "include/crypto/if_alg.h"
              ],
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "vendor": "Linux",
              "versions": [
                {
                  "status": "affected",
                  "version": "2.6.38"
                },
                {
                  "lessThan": "2.6.38",
                  "status": "unaffected",
                  "version": "0",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "5.10.*",
                  "status": "unaffected",
                  "version": "5.10.245",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "5.15.*",
                  "status": "unaffected",
                  "version": "5.15.194",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.1.*",
                  "status": "unaffected",
                  "version": "6.1.154",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.6.*",
                  "status": "unaffected",
                  "version": "6.6.108",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.12.*",
                  "status": "unaffected",
                  "version": "6.12.49",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.16.*",
                  "status": "unaffected",
                  "version": "6.16.9",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "*",
                  "status": "unaffected",
                  "version": "6.17",
                  "versionType": "original_commit_for_fix"
                }
              ]
            }
          ],
          "cpeApplicability": [
            {
              "nodes": [
                {
                  "cpeMatch": [
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "5.10.245",
                      "versionStartIncluding": "2.6.38",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "5.15.194",
                      "versionStartIncluding": "2.6.38",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "6.1.154",
                      "versionStartIncluding": "2.6.38",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "6.6.108",
                      "versionStartIncluding": "2.6.38",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "6.12.49",
                      "versionStartIncluding": "2.6.38",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "6.16.9",
                      "versionStartIncluding": "2.6.38",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "6.17",
                      "versionStartIncluding": "2.6.38",
                      "vulnerable": true
                    }
                  ],
                  "negate": false,
                  "operator": "OR"
                }
              ]
            }
          ],
          "descriptions": [
            {
              "lang": "en",
              "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ncrypto: af_alg - Disallow concurrent writes in af_alg_sendmsg\n\nIssuing two writes to the same af_alg socket is bogus as the\ndata will be interleaved in an unpredictable fashion.  Furthermore,\nconcurrent writes may create inconsistencies in the internal\nsocket state.\n\nDisallow this by adding a new ctx-\u003ewrite field that indiciates\nexclusive ownership for writing."
            }
          ],
          "metrics": [
            {
              "cvssV3_1": {
                "baseScore": 7.8,
                "baseSeverity": "HIGH",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
              },
              "scenarios": [
                {
                  "lang": "en",
                  "value": "AV:L - The vulnerability is reached through the AF_ALG socket family via `socket()`/`bind()`/`sendmsg()`/`recvmsg()` syscalls, which requires local system access. There is no remote or adjacent-network path to `af_alg_sendmsg()`.\nAC:L - The attacker controls both sides of the race entirely \u2014 two of its own threads on a socket it owns \u2014 and can force writer A to park deterministically in `af_alg_wait_for_wmem()` by sizing `SO_SNDBUF` and filling it, then wake it on demand with its own `recvmsg()`. The error exit that leaves `cur == 0` is triggered at will with a deliberately faulting user buffer, so no condition is outside the attacker\u0027s control.\nPR:L - `alg_create()`, `alg_bind()` and `alg_setkey()` perform no capability checks whatsoever, so any unprivileged local user \u2014 including one inside a container or unprivileged user namespace \u2014 can open, bind and write to an AF_ALG skcipher/aead socket. The required modules are auto-loaded on demand via `MODULE_ALIAS_NETPROTO(AF_ALG)` and `request_module(\"algif-%s\")`.\nUI:N - The attacking process performs every step itself \u2014 socket creation, bind, and the two concurrent `sendmsg()` calls. No victim action or interaction of any kind is needed.\nS:U - The corruption is confined to kernel heap objects (`struct af_alg_tsgl`/scatterlist and adjacent slab memory) within the same security authority. No hypervisor, IOMMU, or other trust boundary is crossed.\nC:H - The out-of-bounds scatterlist entry is fabricated from kernel list pointers and is subsequently handed to the cipher by `skcipher_recvmsg`/`aead_recvmsg` via `af_alg_pull_tsgl()`, so arbitrary kernel memory is encrypted/decrypted and returned to userspace. This yields a kernel memory disclosure primitive, not merely a pointer leak.\nI:H - `memcpy_from_msg(page_address(sg_page(sg)) + sg-\u003eoffset + sg-\u003elength, msg, len)` on the underflowed scatterlist writes attacker-controlled data of attacker-chosen length to an address derived from attacker-influenceable heap contents. Combined with heap grooming of the 4KB tsgl allocations, this is a controlled kernel write suitable for privilege escalation.\nA:H - Dereferencing `page_address(sg_page(sg))` on a bogus page_link, and the later `put_page()` on that fabricated page, reliably produce an oops/panic or page refcount corruption. Any unprivileged user can trigger this repeatedly, crashing the machine."
                }
              ]
            }
          ],
          "providerMetadata": {
            "dateUpdated": "2026-08-05T12:06:33.126Z",
            "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "shortName": "Linux"
          },
          "references": [
            {
              "url": "https://git.kernel.org/stable/c/0f28c4adbc4a97437874c9b669fd7958a8c6d6ce"
            },
            {
              "url": "https://git.kernel.org/stable/c/e4c1ec11132ec466f7362a95f36a506ce4dc08c9"
            },
            {
              "url": "https://git.kernel.org/stable/c/1f323a48e9b5ebfe6dc7d130fdf5c3c0e92a07c8"
            },
            {
              "url": "https://git.kernel.org/stable/c/7c4491b5644e3a3708f3dbd7591be0a570135b84"
            },
            {
              "url": "https://git.kernel.org/stable/c/9aee87da5572b3a14075f501752e209801160d3d"
            },
            {
              "url": "https://git.kernel.org/stable/c/45bcf60fe49b37daab1acee57b27211ad1574042"
            },
            {
              "url": "https://git.kernel.org/stable/c/1b34cbbf4f011a121ef7b2d7d6e6920a036d5285"
            }
          ],
          "title": "crypto: af_alg - Disallow concurrent writes in af_alg_sendmsg",
          "x_generator": {
            "engine": "bippy-1.2.0"
          }
        }
      },
      "cveMetadata": {
        "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "assignerShortName": "Linux",
        "cveId": "CVE-2025-39964",
        "datePublished": "2025-10-13T13:48:30.334Z",
        "dateReserved": "2025-04-16T07:20:57.149Z",
        "dateUpdated": "2026-09-19T03:56:17.769Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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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.

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Detection rules are retrieved from Rulezet.

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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.


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