CVE-2025-39964 (GCVE-0-2025-39964)
Vulnerability from cvelistv5 – Published: 2025-10-13 13:48 – Updated: 2026-10-15 01:08Title
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.
Severity
7.8 (High)
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')
Assigner
References
10 references
Impacted products
8 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 | |
| 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 | |
| Siemens | SIMATIC S7-1500 CPU 1518-4 PN/DP MFP |
Affected:
V3.1.6 , < *
(custom)
|
guessed | |
| Siemens | SIMATIC S7-1500 CPU 1518-4 PN/DP MFP |
Affected:
V3.1.7 , < *
(custom)
|
guessed | |
| Siemens | SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP |
Affected:
V3.1.6 , < *
(custom)
|
guessed | |
| Siemens | SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP |
Affected:
V3.1.7 , < *
(custom)
|
guessed | |
| Siemens | SIPLUS S7-1500 CPU 1518-4 PN/DP MFP |
Affected:
V3.1.6 , < *
(custom)
|
guessed | |
| Siemens | SIPLUS S7-1500 CPU 1518-4 PN/DP MFP |
Affected:
V3.1.7 , < *
(custom)
|
guessed |
CISA
Known Exploited Vulnerability - GCVE BCP-07 Compliant
KEV entry ID: 6db5d9c2-b74d-446a-bc33-ce3ebf8d3ac2
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
KEV entry ID: d09a224d-3ea2-4298-afea-8d04b038d5c5
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
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"dateUpdated": "2026-06-11T17:35:29.681Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"references": [
{
"tags": [
"government-resource"
],
"url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-39964"
}
],
"timeline": [
{
"lang": "en",
"time": "2026-09-18T00:00:00.000Z",
"value": "CVE-2025-39964 added to CISA KEV"
}
],
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"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": [
{
"lessThan": "0f28c4adbc4a97437874c9b669fd7958a8c6d6ce",
"status": "affected",
"version": "8ff590903d5fc7f5a0a988c38267a3d08e6393a2",
"versionType": "git"
},
{
"lessThan": "e4c1ec11132ec466f7362a95f36a506ce4dc08c9",
"status": "affected",
"version": "8ff590903d5fc7f5a0a988c38267a3d08e6393a2",
"versionType": "git"
},
{
"lessThan": "1f323a48e9b5ebfe6dc7d130fdf5c3c0e92a07c8",
"status": "affected",
"version": "8ff590903d5fc7f5a0a988c38267a3d08e6393a2",
"versionType": "git"
},
{
"lessThan": "7c4491b5644e3a3708f3dbd7591be0a570135b84",
"status": "affected",
"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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Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.
Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
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.
Vulnerability timeline
Sightings and recorded dates, grouped by day · UTC
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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.
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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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.