CVE-2025-39964 [Low] | Security Vulnerability in Linux Kernel

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.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-02-04	0.06%	0.03%	-0.03%
2	2025-11-26	0.02%	0.06%	+0.04%
3	2025-10-14	—	0.02%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-02-04

0.06%

0.03%

-0.03%

2025-11-26

0.02%

0.06%

+0.04%

2025-10-14

—

0.02%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
3.3	3.1	LOW	`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L` Click to expand Attack vector (AV:L) They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:L) A normal user session is enough; they don’t have to be admin. User interaction (UI:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:N) Doesn’t really leak secrets in a meaningful way. Integrity (I:N) Data isn’t meaningfully altered or forged. Availability (A:L) Might cause slowdowns, glitches, or partial disruption—not a full brick.	1.8	1.4	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

3.3

3.1

LOW

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L Click to expand

Attack vector (AV:L): They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L): Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L): A normal user session is enough; they don’t have to be admin.
User interaction (UI:N): Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U): Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N): Doesn’t really leak secrets in a meaningful way.
Integrity (I:N): Data isn’t meaningfully altered or forged.
Availability (A:L): Might cause slowdowns, glitches, or partial disruption—not a full brick.

1.8

1.4

[email protected]

OS Trackers for CVE-2025-39964

vendor	priority	summary	link
`debian`	not yet assigned	CVE-2025-39964 not yet assigned priority: Debian including 2 source packages (linux, linux-6.1), 6 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 6.	https://security-tracker.debian.org/tracker/CVE-2025-39964
`redhat`	medium	—	https://access.redhat.com/security/cve/CVE-2025-39964
`suse`	medium	CVE-2025-39964 severity moderate: SUSE including 478 source package names (2.1.3-6.124:kernel-default-base-6.4.0-40.1.21.17, 2.1.3-7.105:kernel-default-6.4.0-40.1, …), 719 product×package rows across 44 product lines (Container suse/sl-micro/6.0/base-os-container, Container suse/sl-micro/6.0/kvm-os-container, … (44 product lines)): Fixed 456, Known Affected 231, First Fixed 32.	https://www.suse.com/security/cve/CVE-2025-39964/
`ubuntu`	medium	CVE-2025-39964 medium priority: Ubuntu including 157 source packages (linux, linux-allwinner-5.19, …), 1405 status rows across 9 suites (bionic, focal, jammy, noble, plucky, questing, trusty, upstream, xenial): DNE 1010, released 202, ignored 166, not-affected 18, needed 4, pending 3, needs-triage 2.	https://ubuntu.com/security/CVE-2025-39964

Affected software / configurations for CVE-2025-39964

Vendor	Product	Version	Raw CPE
linux	linux_kernel	>= 2.6.38, < 5.10.245	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 5.11, < 5.15.194	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 5.16, < 6.1.154	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 6.2, < 6.6.108	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 6.7, < 6.12.49	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 6.13, < 6.16.9	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	6.17	cpe:2.3:o:linux:linux_kernel:6.17:rc1::::::
linux	linux_kernel	6.17	cpe:2.3:o:linux:linux_kernel:6.17:rc2::::::
linux	linux_kernel	6.17	cpe:2.3:o:linux:linux_kernel:6.17:rc3::::::
linux	linux_kernel	6.17	cpe:2.3:o:linux:linux_kernel:6.17:rc4::::::
linux	linux_kernel	6.17	cpe:2.3:o:linux:linux_kernel:6.17:rc5::::::
linux	linux_kernel	6.17	cpe:2.3:o:linux:linux_kernel:6.17:rc6::::::

References for CVE-2025-39964

URL	Tags
https://git.kernel.org/stable/c/0f28c4adbc4a97437874c9b669fd7958a8c6d6ce	Patch
https://git.kernel.org/stable/c/1b34cbbf4f011a121ef7b2d7d6e6920a036d5285	Patch
https://git.kernel.org/stable/c/1f323a48e9b5ebfe6dc7d130fdf5c3c0e92a07c8	Patch
https://git.kernel.org/stable/c/45bcf60fe49b37daab1acee57b27211ad1574042	Patch
https://git.kernel.org/stable/c/7c4491b5644e3a3708f3dbd7591be0a570135b84	Patch
https://git.kernel.org/stable/c/9aee87da5572b3a14075f501752e209801160d3d	Patch
https://git.kernel.org/stable/c/e4c1ec11132ec466f7362a95f36a506ce4dc08c9	Patch

URL

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

Exploit prediction scoring system (EPSS) score for CVE-2025-39964

Common vulnerability scoring system (CVSS) metrics for CVE-2025-39964

Weakness enumeration for CVE-2025-39964

OS Trackers for CVE-2025-39964

Affected software / configurations for CVE-2025-39964

References for CVE-2025-39964