Vulnerability in libsixel (CVE-2026-44638)
Summary
Vulnerability in libsixel (CVE-2026-44638). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to 1.8.7-r2 or later.
Original description
The description as published by the source.
libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. From to 1.8.7-r1, a wrong NULL check after an allocation call in sixel_decode_raw and sixel_decode causes a NULL pointer dereference whenever the allocation fails. The check tests the address of the output parameter (always non-NULL) instead of the value the malloc returned. On allocation failure, the function continues and writes through a NULL pointer, crashing the process. This is a denial of service against any caller of these public APIs that hits a low-memory condition. This vulnerability is fixed in 1.8.7-r2.
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-2026-44638 has been found in libsixel.
Risk of unauthorized operations or information disclosure. CVSS score: 2.5/10.
What to do: upgrade libsixel to 1.8.7-r2 or later.
If unsure, ask your IT team or search "libsixel CVE-2026-44638" on the vendor's site.
CVE-2026-44638 (libsixel) — CWE-476 / CVSS v3 2.5
Attack vector: local / unauthenticated
Patched: 1.8.7-r2 — apply immediately
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-476) exists in libsixel.
Check the vendor advisory for the affected versions of libsixel.
Severity: Low (CVSS 2.5/10). Risk of unauthorized operations or information disclosure.
Update to 1.8.7-r2.
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 'libsixel' . 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
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1Identify exposure identify
grep -r 'libsixel' . | 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
libsixelを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade libsixel to 1.8.7-r2ステージング環境で 1.8.7-r2 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
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3Post-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-2026-44638 libsixel
- Ubuntu UBUNTU-CVE-2026-44638 libsixel
References
- advisory github.com
- advisory github.com
- advisory nvd.nist.gov