Vulnerability in cosign (CVE-2026-39395)
Summary
Vulnerability in cosign (CVE-2026-39395). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to 2.6.3, 3.0.6 or later.
Original description
The description as published by the source.
Cosign provides code signing and transparency for containers and binaries. Prior to 3.0.6 and 2.6.3, cosign verify-blob-attestation may erroneously report a "Verified OK" result for attestations with malformed payloads or mismatched predicate types. For old-format bundles and detached signatures, this was due to a logic flaw in the error handling of the predicate type validation. For new-format bundles, the predicate type validation was bypassed completely. This vulnerability is fixed in 3.0.6 and 2.6.3.
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-2026-39395 has been found in cosign.
Risk of unauthorized operations or information disclosure. CVSS score: 4.3/10.
What to do: upgrade cosign to 2.6.3, 3.0.6 or later.
If unsure, ask your IT team or search "cosign CVE-2026-39395" on the vendor's site.
CVE-2026-39395 (cosign) — CWE-754 / CVSS v3 4.3
Attack vector: remote (network-reachable) / unauthenticated
Patched: 2.6.3, 3.0.6 — 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-754) exists in cosign.
Check the vendor advisory for the affected versions of cosign.
Severity: Medium (CVSS 4.3/10). Risk of unauthorized operations or information disclosure.
Update to 2.6.3, 3.0.6.
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 'cosign' . 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 'cosign' . | 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
cosign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 cosign to 2.6.3, 3.0.6ステージング環境で 2.6.3, 3.0.6 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。
-
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。
Affected packages
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Debian DEBIAN-CVE-2026-39395 cosign
- Ubuntu UBUNTU-CVE-2026-39395 cosign
References
- advisory github.com
- advisory nvd.nist.gov
- advisory github.com
- package github.com