Vulnerability in Gnu Glibc (CVE-2026-3904)
Summary
Vulnerability in Gnu Glibc (CVE-2026-3904). Risk of unauthorized operations or information disclosure.
Original description
The description as published by the source.
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.
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-3904 has been found in Gnu Glibc.
Risk of unauthorized operations or information disclosure. CVSS score: 6.2/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Gnu Glibc CVE-2026-3904" on the vendor's site.
CVE-2026-3904 (Gnu Glibc) — CWE-366 / CVSS v3 6.2
Attack vector: local / unauthenticated / no user interaction
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-366) exists in Gnu Glibc.
Check the vendor advisory for the affected versions of Gnu Glibc.
Severity: Medium (CVSS 6.2/10). Risk of unauthorized operations or information disclosure.
Update to the patched release per vendor advisory.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'Glibc' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'Glibc' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
Glibcを grep し、稼働しているサービス・バージョンを把握する。 -
2Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Debian DEBIAN-CVE-2026-3904 glibc Fixed in: 2.36-9
References
- web sourceware.org
- web sourceware.org
- web sourceware.org
- web sourceware.org
- web openwall.com
- web cert-portal.siemens.com
- web nvd.nist.gov
- web github.com