Vulnerability in io.netty:netty-handler-ssl-ocsp (CVE-2026-56821)
Summary
Vulnerability in io.netty:netty-handler-ssl-ocsp (CVE-2026-56821). Confidential information can be exposed externally. Exploitable via OcspServerCertificateValidator. Mitigation: upgrade to 4.1.136.Final or later.
Original description
The description as published by the source.
Netty is an asynchronous, event-driven network application framework. Prior to versions 4.1.136.Final and 4.2.16.Final, the OcspServerCertificateValidator flags an out-of-date OCSP response but does not stop processing it, so an expired GOOD response is still reported as VALID, letting an on-path attacker replay a stale GOOD response to bypass revocation of a since-revoked certificate. Exploitation can lead to certificate revocation bypass via replay of an expired OCSP response. Any application using OcspServerCertificateValidator is affected; a revoked certificate can be accepted. This issue has been fixed in versions 4.1.136.Final and 4.2.16.Final.
Source: GitHub Security Advisories (Global) 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-2026-56821 has been found in io.netty:netty-handler-ssl-ocsp.
Attackers can target a specific entry point like OcspServerCertificateValidator over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 7.4/10.
What to do: upgrade io.netty:netty-handler-ssl-ocsp to 4.1.136.Final or later.
If unsure, ask your IT team or search "io.netty:netty-handler-ssl-ocsp CVE-2026-56821" on the vendor's site.
CVE-2026-56821 (io.netty:netty-handler-ssl-ocsp) — CWE-299 / CVSS v3 7.4
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: OcspServerCertificateValidator / VALID / return / OcspValidationEvent
Patched: 4.1.136.Final — 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-299) exists in io.netty:netty-handler-ssl-ocsp. Attackers reach the vulnerable code path via OcspServerCertificateValidator without authentication.
Check the vendor advisory for the affected versions of io.netty:netty-handler-ssl-ocsp. Attack surface: OcspServerCertificateValidator / VALID / return / OcspValidationEvent.
Severity: High (CVSS 7.4/10). Confidential information can be exposed externally.
Update to 4.1.136.Final.
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. Audit SBOM/dependencies 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
Audit SBOM/dependencies for affected components.資産台帳・SBOM・依存マニフェストで io.netty:netty-handler-ssl-ocsp を使っているサービスとバージョンを洗い出す。
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2Apply patch patch
Upgrade io.netty:netty-handler-ssl-ocsp to 4.1.136.Finalステージング環境で 4.1.136.Final 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。
Affected packages
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Debian DEBIAN-CVE-2026-56821 netty
- Ubuntu UBUNTU-CVE-2026-56821 netty
References
- advisory github.com
- advisory github.com
- advisory nvd.nist.gov
- web github.com
- web github.com
- web github.com