Vulnerability in Netty (CVE-2026-93575)
Summary
Vulnerability in Netty (CVE-2026-93575). Risk of unauthorized operations or information disclosure. Exploitable via maxBytesInMessage.
Original description
The description as published by the source.
Summary
Netty's fix for CVE-2026-44248 is incomplete. The decoder checks if the MQTT packet's Remaining Length exceeds maxBytesInMessage, but fails to validate the Properties Length against the Remaining Length. An attacker can bypass the size limit by sending a small Remaining Length but an enormous Properties Length. This forces Netty to buffer and parse millions of properties, allowing an unauthenticated remote attacker to trigger excessive memory and CPU consumption, leading to OutOfMemoryError.
Details
In io.netty.handler.codec.mqtt.MqttDecoder, the decodeProperties() helper method reads totalPropertiesLength and attempts to parse that many bytes. If the buffer lacks the full length, a Signal is thrown. The catch block inside decode() only enforces maxBytesInMessage against bytesRemainingBeforeVariableHeader (the packet's Remaining Length).
By sending a CONNECT packet with a small Remaining Length but a huge Properties Length, the size check passes. ReplayingDecoder then buffers data from the network until the huge Properties Length is reached, parsing millions of UserProperty objects and exhausting CPU and memory.
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-2026-93575 has been found in Netty.
Attackers can target a specific entry point like maxBytesInMessage over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 7.5/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Netty CVE-2026-93575" on the vendor's site.
CVE-2026-93575 (Netty) — CWE-1035 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: maxBytesInMessage / io.netty.handler.codec.mqtt.MqttDecoder / totalPropertiesLength / Signal
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-1035) exists in Netty. Attackers reach the vulnerable code path via maxBytesInMessage without authentication.
Check the vendor advisory for the affected versions of Netty. Attack surface: maxBytesInMessage / io.netty.handler.codec.mqtt.MqttDecoder / totalPropertiesLength / Signal.
Severity: High (CVSS 7.5/10). Risk of unauthorized operations or information disclosure.
Update to the patched release per vendor advisory.
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 'Netty' . 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 'Netty' . | 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
Nettyを grep し、稼働しているサービス・バージョンを把握する。 -
2Post-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-2026-93575 netty
- Ubuntu UBUNTU-CVE-2026-93575 netty
References
- web access.redhat.com
- web bugzilla.redhat.com
- web nvd.nist.gov
- web github.com