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🛡️ CVE-2026-3904 — glibc

🟡 CVSS 6.2 — Medium ⚠️ Exploit Public CWE-366 NVD
6.2
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Calling NSS-backed functions that support caching via nscd may call the

nscd client side code and in the GNU C Library version 2.36 under high

load on x86_64 systems, the client may call memcmp on inputs that are

concurrently modified by other processes or threads and crash.

The nscd client in the GNU C Library uses the memcmp function with

inputs that may be concurrently modified by another thread, potentially

resulting in spurious cache misses, which in itself is not a security

issue.  However in the GNU C Library version 2.36 an optimized

implementation of memcmp was introduced for x86_64 which could crash

when invoked with such undefined behaviour, turning this into a

potential crash of the nscd client and the application that uses it.

This implementation was backported to the 2.35 branch, making the nscd

client in that branch vulnerable as well.  Subsequently, the fix for

this issue was backported to all vulnerable branches in the GNU C

Library repository.

It is advised that distributions that may have cherry-picked the memcpy

SSE2 optimization in their copy of the GNU C Library, also apply the fix

to avoid the potential crash in the nscd client.

How this vulnerability can be exploited

This issue can be reached with local access to the system, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity none, availability high.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

  • Attack vector: Local — a local account, shell or session on the host is needed.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Privileges required: None — an unauthenticated stranger can try it.
  • User interaction: None — nobody has to be tricked into anything.
  • Scope: Unchanged — the damage stays inside the vulnerable component.
  • Confidentiality impact: None.
  • Integrity impact: None.
  • Availability impact: High — total loss, or loss the attacker controls.

Weakness class

CVE-2026-3904 is classified as CWE-366: Race Condition within a Thread. If two threads of execution use a resource simultaneously, there exists the possibility that resources may be used while invalid, in turn making the state of execution undefined.

Affected software

CVE-2026-3904 is recorded against 1 package.

  • glibc (from 2.35 up to 2.37)

Timeline and source

Published on 11 March 2026 and last revised on 14 July 2026. A public exploit is known to exist, which raises the urgency of patching considerably. A vendor advisory or fix has been published. Record sourced from NVD.

References

sourceware.org
sourceware.org
sourceware.org
sourceware.org
www.openwall.com
cert-portal.siemens.com

Other advisories for this package

glibc has other advisories on record. If you are patching this one, these are worth checking on the same host:

Same weakness in other software

These advisories are the same class of weakness (CWE-366: Race Condition within a Thread) in other software:

CVE-2026-3904 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity MEDIUM
CVSS Score 6.2
CVSS Vector CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE CWE-366
Public Exploit ⚠️ Yes
Source NVD
Published 2026-03-11
Updated 2026-08-20
Modified 2026-07-14

Affected Packages

Software From version Fixed in
glibc 2.35 2.37

Similar Threats

Exploit Protection

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CVE-2026-3904 carries CVSS 6.2 Medium rating and a public exploit already exists. BotEraser checks your installation against this and other known CVE records, and blocks IPs associated with exploit activity.

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ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the vulnerabilities listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.

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