FalehSec Exploited-vulnerability triage · joined from CISA KEV, NVD CVSS and EPSS

CVE-2025-39964

Linux · Kernel · Linux Kernel Race Condition Vulnerability

Verdict
Patch on your normal cycle · actively exploited, not reachable unauthenticated from the internet, and in the top half of CVEs by near-term exploitation probability

Added to CISA KEV 2026-09-18 · exploited in the wild for 9 days

What an attacker can reach How likely Time What CISA says to do Sources All 545

What an attacker can reach

CVSS 7.8 HIGH. The score is a summary; these three components are the part that decides whether something scanning the internet can use it.

Attack vectorlocalrequires local access to the machine
Privileges requiredlowneeds some credentials, so a fully anonymous attacker cannot reach it directly
User interactionnonecan be triggered with nobody interacting with the page or request
Base vectorCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
WeaknessCWE-362

This describes the vulnerability. It says nothing about whether your systems run it.

How likely

EPSS puts the probability of exploitation in the next 30 days at 0.0100, which places it in the top half of all tracked CVEs. The percentile is the more useful half: 0.18 in absolute terms sounds low until you know most of the internet-facing software in the world scores under that.

EPSS probability0.0100
Percentile0.612 — top half

Time

Added to KEV2026-09-18
Days exploited9
Federal remediation duenot set
Ransomware useno known ransomware campaign use

What CISA says to do

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.

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.

Sources