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CVE-2025-39964· NVD / CVE Program· CNA Linux

crypto: af_alg - Disallow concurrent writes in af_alg_sendmsg

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.

MediumCVSS 5.5 · v3.1KEVWeaponized Fix available
Published
Oct 13, 2025
Updated
Sep 19, 2026
EPSS
1.0% · 61th percentile
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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 · 1.0%

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 government agencies: Sep 21, 2026.

Affected systems

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

Affected versions

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

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

Package-level exposure

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

EcosystemPackageAffected rangeFix
AlmaLinux:8bpftoolbefore 4.18.0-553.166.1.el8_104.18.0-553.166.1.el8_10
AlmaLinux:8kernelbefore 4.18.0-553.166.1.el8_104.18.0-553.166.1.el8_10
AlmaLinux:8kernel-abi-stablelistsbefore 4.18.0-553.166.1.el8_104.18.0-553.166.1.el8_10
AlmaLinux:8kernel-corebefore 4.18.0-553.166.1.el8_104.18.0-553.166.1.el8_10
AlmaLinux:8kernel-cross-headersbefore 4.18.0-553.166.1.el8_104.18.0-553.166.1.el8_10
AlmaLinux:8kernel-debugbefore 4.18.0-553.166.1.el8_104.18.0-553.166.1.el8_10
AlmaLinux:8kernel-debug-corebefore 4.18.0-553.166.1.el8_104.18.0-553.166.1.el8_10
AlmaLinux:8kernel-debug-develbefore 4.18.0-553.166.1.el8_104.18.0-553.166.1.el8_10
AlmaLinux:8kernel-debug-modulesbefore 4.18.0-553.166.1.el8_104.18.0-553.166.1.el8_10
AlmaLinux:8kernel-debug-modules-extrabefore 4.18.0-553.166.1.el8_104.18.0-553.166.1.el8_10
AlmaLinux:8kernel-develbefore 4.18.0-553.166.1.el8_104.18.0-553.166.1.el8_10
AlmaLinux:8kernel-docbefore 4.18.0-553.166.1.el8_104.18.0-553.166.1.el8_10
AlmaLinux:8kernel-headersbefore 4.18.0-553.166.1.el8_104.18.0-553.166.1.el8_10
AlmaLinux:8kernel-modulesbefore 4.18.0-553.166.1.el8_104.18.0-553.166.1.el8_10
AlmaLinux:8kernel-modules-extrabefore 4.18.0-553.166.1.el8_104.18.0-553.166.1.el8_10
AlmaLinux:8kernel-rtbefore 4.18.0-553.166.1.rt7.507.el8_104.18.0-553.166.1.rt7.507.el8_10
AlmaLinux:8kernel-rt-corebefore 4.18.0-553.166.1.rt7.507.el8_104.18.0-553.166.1.rt7.507.el8_10
AlmaLinux:8kernel-rt-debugbefore 4.18.0-553.166.1.rt7.507.el8_104.18.0-553.166.1.rt7.507.el8_10
AlmaLinux:8kernel-rt-debug-corebefore 4.18.0-553.166.1.rt7.507.el8_104.18.0-553.166.1.rt7.507.el8_10
AlmaLinux:8kernel-rt-debug-develbefore 4.18.0-553.166.1.rt7.507.el8_104.18.0-553.166.1.rt7.507.el8_10
AlmaLinux:8kernel-rt-debug-modulesbefore 4.18.0-553.166.1.rt7.507.el8_104.18.0-553.166.1.rt7.507.el8_10
AlmaLinux:8kernel-rt-debug-modules-extrabefore 4.18.0-553.166.1.rt7.507.el8_104.18.0-553.166.1.rt7.507.el8_10
AlmaLinux:8kernel-rt-develbefore 4.18.0-553.166.1.rt7.507.el8_104.18.0-553.166.1.rt7.507.el8_10
AlmaLinux:8kernel-rt-modulesbefore 4.18.0-553.166.1.rt7.507.el8_104.18.0-553.166.1.rt7.507.el8_10

+96

Other highest-scoring records for the same primary product.

  • 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
  • CVE-2016-5195Race condition in mm/gup.c in the Linux kernel 2.x through 4.x before 4.8.3 allows local users to gain privileges by leveraging incorrect haKEV
    83Now
  • CVE-2019-13272In the Linux kernel before 5.1.17, ptrace_link in kernel/ptrace.c mishandles the recording of the credentials of a process that wants to creKEV
    77This week
  • CVE-2013-6282The (1) get_user and (2) put_user API functions in the Linux kernel before 3.5.5 on the v6k and v7 ARM platforms do not validate certain addKEV
    77This week
  • CVE-2013-2094The perf_swevent_init function in kernel/events/core.c in the Linux kernel before 3.8.9 uses an incorrect integer data type, which allows loKEV
    77This week

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)
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)
Red Hat:bpftool0:4.18.0-553.166.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
Red Hat:bpftool-debuginfo0:4.18.0-553.166.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
Red Hat:kernel0:4.18.0-553.166.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
Red Hat:kernel-abi-stablelists0:4.18.0-553.166.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
Red Hat:kernel-core0:4.18.0-553.166.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
Red Hat:kernel-debug0:4.18.0-553.166.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)

+21

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+31 d
  3. CISA KEV+340 d
  4. TodaySep 29, 2026+352 d
EPSS, last 120 days+1% in 7 days

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

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

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

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.

Noroxi analysis

No Noroxi analysis for this record yet

We don't hand-write analysis for all 385,000+ vulnerabilities; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.

We use this product, ask for help

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

All records