Vulnerability in krb5 (DEBIAN-CVE-2026-40356)
Summary
Vulnerability in krb5 (DEBIAN-CVE-2026-40356). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to 1.18.3-6+deb11u8 or later.
Original description
The description as published by the source.
In MIT Kerberos 5 (aka krb5) before 1.22.3, there is an integer underflow and resultant out-of-bounds read if an application calls gss_accept_sec_context() on a system with a NegoEx mechanism registered in /etc/gss/mech. An unauthenticated remote attacker can trigger this, possibly causing the process to terminate in parse_message.
Source: OSV.dev (Open Source Vulnerabilities) OSV
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 DEBIAN-CVE-2026-40356 has been found in krb5.
Risk of unauthorized operations or information disclosure.
What to do: upgrade krb5 to 1.18.3-6+deb11u8 or later.
If unsure, ask your IT team or search "krb5 DEBIAN-CVE-2026-40356" on the vendor's site.
DEBIAN-CVE-2026-40356 (krb5)
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Patched: 1.18.3-6+deb11u8 — 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 (unclassified) exists in krb5.
Check the vendor advisory for the affected versions of krb5.
Severity: ?. Risk of unauthorized operations or information disclosure.
Update to 1.18.3-6+deb11u8.
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 'krb5' . 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 'krb5' . | 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
krb5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 krb5 to 1.18.3-6+deb11u8ステージング環境で 1.18.3-6+deb11u8 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
References
- advisory security-tracker.debian.org