Vulnerability in Libxfont (CVE-2026-56003)
Summary
Vulnerability in Libxfont (CVE-2026-56003). Successful exploitation can lead to full system takeover.
Original description
The description as published by the source.
A heap buffer overflow due to missing size checking in the property buffer when parsing PCF files in libXfont2 ComputeScaledProperties() before libXfont2 before 2.0.8 could be used by attackers using authenticated X clients to execute code within the X server.
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-2026-56003 has been found in Libxfont.
Successful exploitation can lead to full system takeover. CVSS score: 8.5/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Libxfont CVE-2026-56003" on the vendor's site.
CVE-2026-56003 (Libxfont) — CWE-122 / CVSS v3 8.5
Attack vector: remote (network-reachable) / 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-122) exists in Libxfont.
Check the vendor advisory for the affected versions of Libxfont.
Severity: High (CVSS 8.5/10). Successful exploitation can lead to full system takeover.
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 'Libxfont' . 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 'Libxfont' . | 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
Libxfont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-2026-56003 libxfont Fixed in: 1:2.0.6-1+deb12u1
- Ubuntu UBUNTU-CVE-2026-56003 libxfont Fixed in: 1:1.4.7-1ubuntu0.4+esm2
References
- patch meissner@suse.de
- patch meissner@suse.de
- web nvd.nist.gov
- web github.com