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NVD / CVE Program· CNA Linux

CVE-2025-39964: crypto: af_alg - Disallow concurrent writes in af_alg_sendmsg

MediumCVSS 5.5 · v3.1KEVWeaponized Fix available

Noroxi assessment

Priority: Plan (action score 52/100)

  • CISA has confirmed exploitation in the wild (Sep 18, 2026). Remediation deadline for US federal agencies: Sep 21, 2026.
  • Probability of exploitation in the next 30 days: 1.6% (FIRST EPSS); higher than 76.2% of all records.
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: Linux Linux 0f28c4adbc4a97437874c9b669fd7958a8c6d6ce, 1b34cbbf4f011a121ef7b2d7d6e6920a036d5285, 1f323a48e9b5ebfe6dc7d130fdf5c3c0e92a07c8; azl3 kernel 6.6.104.2-4 on Azure Linux 3.0 6.6.112.1-1.
  • Severity is disputed: the assigning authority (CNA) scores it 7.8, NVD 5.5.

Add it to your regular patch cycle. Upgrade to Linux Linux 0f28c4adbc4a97437874c9b669fd7958a8c6d6ce, 1b34cbbf4f011a121ef7b2d7d6e6920a036d5285, 1f323a48e9b5ebfe6dc7d130fdf5c3c0e92a07c8; azl3 kernel 6.6.104.2-4 on Azure Linux 3.0 6.6.112.1-1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · CISA KEV · FIRST EPSS

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.

Published
Oct 13, 2025
Updated
Nov 10, 2026
EPSS
1.6% · 76th percentile

Report tools

JSON

Action score

52

Plan

Add it to your regular patch cycle.

CVSS
22 / 40 · 5.5 / 10
CISA KEV
30 / 30 · Listed
EPSS
0 / 30 · 1.6%

CISA SSVC decision

Exploitation
active
Automatable
no
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
5.5
CNA · Linux
7.8
2.3 point gap

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

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Actively exploited in the wild

CISA added this to its Known Exploited Vulnerabilities catalog on Sep 18, 2026. That signals real attacks, not theory.

Remediation deadline for US federal agencies: Sep 21, 2026.

Get told when this record changes

  • In CISA KEV: exploitation in the wild confirmed
  • Weaponized exploit exists
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2025-39964

When you'll hear from us

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  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
linuxlinux kernel
siemenssimatic s7-1500 cpu 1518-4 pn/dp mfp firmware
siemenssimatic s7-1500 cpu 1518-4 pn/dp mfp
siemenssimatic s7-1500 cpu 1518f-4 pn/dp mfp firmware
siemenssimatic s7-1500 cpu 1518f-4 pn/dp mfp

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 2.6.38affected
    • 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 and later · before 0f28c4adbc4a97437874c9b669fd7958a8c6d6ceaffected · git
    • 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 and later · before e4c1ec11132ec466f7362a95f36a506ce4dc08c9affected · git
    • 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 and later · before 1f323a48e9b5ebfe6dc7d130fdf5c3c0e92a07c8affected · git
    • 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 and later · before 7c4491b5644e3a3708f3dbd7591be0a570135b84affected · git
    • 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 and later · before 9aee87da5572b3a14075f501752e209801160d3daffected · git
    • 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 and later · before 45bcf60fe49b37daab1acee57b27211ad1574042affected · git
    • 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 and later · before 1b34cbbf4f011a121ef7b2d7d6e6920a036d5285affected · git
    • before 2.6.38not affected · semver
    • 5.10.245 and later · up to and including 5.10.*not affected · semver
Affected versions · NVD (9)

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • linux linux kernel2.6.38 and later · before 5.10.245
  • linux linux kernel5.11 and later · before 5.15.194
  • linux linux kernel5.16 and later · before 6.1.154
  • linux linux kernel6.2 and later · before 6.6.108
  • linux linux kernel6.7 and later · before 6.12.49
  • linux linux kernel6.13 and later · before 6.16.9
  • linux linux kernel6.17
  • siemens simatic s7-1500 cpu 1518-4 pn/dp mfp firmware3.1.6 and later
  • siemens simatic s7-1500 cpu 1518f-4 pn/dp mfp firmware3.1.6 and later

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
AlmaLinux:10kernel-64k-debug-develbefore 6.12.0-211.58.1.el10_26.12.0-211.58.1.el10_2
AlmaLinux:10kernel-64k-debug-devel-matchedbefore 6.12.0-211.58.1.el10_26.12.0-211.58.1.el10_2
AlmaLinux:10kernel-64k-develbefore 6.12.0-211.58.1.el10_26.12.0-211.58.1.el10_2
AlmaLinux:10kernel-64k-devel-matchedbefore 6.12.0-211.58.1.el10_26.12.0-211.58.1.el10_2
AlmaLinux:10kernel-cross-headersbefore 6.12.0-211.58.1.el10_26.12.0-211.58.1.el10_2
AlmaLinux:10kernel-debugbefore 6.12.0-211.58.1.el10_26.12.0-211.58.1.el10_2
AlmaLinux:10kernel-debug-corebefore 6.12.0-211.58.1.el10_26.12.0-211.58.1.el10_2
AlmaLinux:10kernel-debug-develbefore 6.12.0-211.58.1.el10_26.12.0-211.58.1.el10_2
AlmaLinux:10kernel-debug-devel-matchedbefore 6.12.0-211.58.1.el10_26.12.0-211.58.1.el10_2
AlmaLinux:10kernel-debug-modulesbefore 6.12.0-211.58.1.el10_26.12.0-211.58.1.el10_2
AlmaLinux:10kernel-debug-modules-corebefore 6.12.0-211.58.1.el10_26.12.0-211.58.1.el10_2
AlmaLinux:10kernel-debug-modules-extrabefore 6.12.0-211.58.1.el10_26.12.0-211.58.1.el10_2
AlmaLinux:10kernel-debug-uki-virtbefore 6.12.0-211.58.1.el10_26.12.0-211.58.1.el10_2
AlmaLinux:10kernel-develbefore 6.12.0-211.58.1.el10_26.12.0-211.58.1.el10_2
AlmaLinux:10kernel-devel-matchedbefore 6.12.0-211.58.1.el10_26.12.0-211.58.1.el10_2
AlmaLinux:10kernel-docbefore 6.12.0-211.58.1.el10_26.12.0-211.58.1.el10_2
AlmaLinux:10kernel-headersbefore 6.12.0-211.58.1.el10_26.12.0-211.58.1.el10_2
AlmaLinux:10kernel-modulesbefore 6.12.0-211.58.1.el10_26.12.0-211.58.1.el10_2
AlmaLinux:10kernel-modules-corebefore 6.12.0-211.58.1.el10_26.12.0-211.58.1.el10_2
AlmaLinux:10kernel-modules-extrabefore 6.12.0-211.58.1.el10_26.12.0-211.58.1.el10_2
AlmaLinux:10kernel-modules-extra-matchedbefore 6.12.0-211.58.1.el10_26.12.0-211.58.1.el10_2
AlmaLinux:10kernel-rtbefore 6.12.0-211.58.1.el10_26.12.0-211.58.1.el10_2
AlmaLinux:10kernel-rt-64kbefore 6.12.0-211.58.1.el10_26.12.0-211.58.1.el10_2
AlmaLinux:10kernel-rt-64k-corebefore 6.12.0-211.58.1.el10_26.12.0-211.58.1.el10_2

+96

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV
    90Now
  • CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe…KEV
    89Now
  • CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV
    85Now

Published before and after this one in the same product

  • ← EarlierCVE-2025-39962Oct 9, 2025 · rxrpc: Fix untrusted unsigned subtract
    31Monitor
  • ← EarlierCVE-2025-39963Oct 9, 2025 · io_uring: fix incorrect io_kiocb reference in io_link_skb
    31Monitor
  • Later →CVE-2025-39965Oct 13, 2025 · xfrm: xfrm_alloc_spi shouldn't use 0 as SPI
    22Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux0f28c4adbc4a97437874c9b669fd7958a8c6d6ceVendor (CNA)
Linux Linux1b34cbbf4f011a121ef7b2d7d6e6920a036d5285Vendor (CNA)
Linux Linux1f323a48e9b5ebfe6dc7d130fdf5c3c0e92a07c8Vendor (CNA)
Linux Linux45bcf60fe49b37daab1acee57b27211ad1574042Vendor (CNA)
Linux Linux7c4491b5644e3a3708f3dbd7591be0a570135b84Vendor (CNA)
Linux Linux9aee87da5572b3a14075f501752e209801160d3dVendor (CNA)
Linux Linuxe4c1ec11132ec466f7362a95f36a506ce4dc08c9Vendor (CNA)
azl3 kernel 6.6.104.2-4 on Azure Linux 3.06.6.112.1-1 · CBL-Mariner ReleasesMicrosoft (MSRC)
almalinux:bpftool4.18.0-553.166.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel4.18.0-553.166.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-abi-stablelists4.18.0-553.166.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-core4.18.0-553.166.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-cross-headers4.18.0-553.166.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug4.18.0-553.166.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug-core4.18.0-553.166.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug-devel4.18.0-553.166.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug-modules4.18.0-553.166.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug-modules-extra4.18.0-553.166.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-devel4.18.0-553.166.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-doc4.18.0-553.166.1.el8_10 · AlmaLinux:8Package registry (OSV)
debian:linux6.1.158-1 · Debian:12Package registry (OSV)
debian:linux-6.16.1.158-1~deb11u1 · Debian:11Package registry (OSV)
opensuse:dtb-aarch646.4.0-150600.23.92.1 · openSUSE:Leap 15.6Package registry (OSV)
opensuse:kernel-64kb6.4.0-150600.23.92.1 · openSUSE:Leap 15.6Package registry (OSV)
opensuse:kernel-debug6.4.0-150600.23.92.1 · openSUSE:Leap 15.6Package registry (OSV)
opensuse:kernel-default6.4.0-150600.23.92.1 · openSUSE:Leap 15.6Package registry (OSV)
opensuse:kernel-default-base6.4.0-150600.23.92.1.150600.12.42.2 · openSUSE:Leap 15.6Package registry (OSV)
opensuse:kernel-docs6.4.0-150600.23.92.1 · openSUSE:Leap 15.6Package registry (OSV)
opensuse:kernel-kvmsmall6.4.0-150600.23.92.1 · openSUSE:Leap 15.6Package registry (OSV)
opensuse:kernel-obs-build6.4.0-150600.23.92.1 · openSUSE:Leap 15.6Package registry (OSV)

+31

Exploit status

Weaponized

A ready exploit tool or active in-the-wild use is known for this vulnerability. This should be your top priority.

Evidence

  • Proof-of-concept repository on GitHub ×2

Noroxi does not host or link to exploit code. Metasploit module names and Nuclei template ids are shown (names, not code); Exploit-DB entries and PoC repositories are given as counts only.

Public exploit evidence
SourceKindDate
Proof-of-concept repository on GitHubstars:32025-11-13
Proof-of-concept repository on GitHubstars:02026-09-20

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

  1. Published
  2. First PoC+30 d
  3. CISA KEV+339 d
  4. TodayNov 14, 2026+396 d
EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Not on record for this CVE: patch commit or PR link · researcher credit · variant or chain candidate · public bounty program.

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

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

CVSS vector

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

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

References

Show all references (9 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records