Vulnerability in io.netty:netty-codec-http (CVE-2026-59921)
Summary
Vulnerability in io.netty:netty-codec-http (CVE-2026-59921). Data can be tampered with by attackers. Exploitable via HttpPostRequestEncoder. 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, HttpPostRequestEncoder constructs multipart HTTP request bodies by directly concatenating user-supplied filenames and field names into Content-Disposition MIME headers without validating or sanitizing CRLF characters (\r\n). Since MIME headers are delimited by CRLF, an attacker who controls the filename can inject arbitrary MIME headers into the multipart body part. The root cause is that neither the encoder nor the FileUpload implementations' setFilename() methods, which only check for null, neutralize CRLF characters before the filename is embedded into the header. 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-2026-59921 has been found in io.netty:netty-codec-http.
Attackers can target a specific entry point like HttpPostRequestEncoder over the network to misuse the product.
Data can be tampered with by attackers. CVSS score: 5.7/10.
What to do: upgrade io.netty:netty-codec-http to 4.1.136.Final or later.
If unsure, ask your IT team or search "io.netty:netty-codec-http CVE-2026-59921" on the vendor's site.
CVE-2026-59921 (io.netty:netty-codec-http) — CWE-93 / CVSS v3 5.7
Attack vector: adjacent-network / no user interaction
Attack surface: HttpPostRequestEncoder / HttpPostRequestEncoder.java / FileUpload
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-93) exists in io.netty:netty-codec-http. Attackers reach the vulnerable code path via HttpPostRequestEncoder.
Check the vendor advisory for the affected versions of io.netty:netty-codec-http. Attack surface: HttpPostRequestEncoder / HttpPostRequestEncoder.java / FileUpload.
Severity: Medium (CVSS 5.7/10). Data can be tampered with by attackers.
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-codec-http 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-codec-http 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-2026-59921 netty
- Ubuntu UBUNTU-CVE-2026-59921 netty
References
- advisory github.com
- advisory github.com
- advisory nvd.nist.gov
- web github.com
- web github.com
- web github.com