What’s Vulnerable › Vulnerabilities

CVE-2026-56745: Netty SpdyHttpDecoder: ByteBuf Reference Leak on RST_STREAM Leads to Native Memory Exhaustion

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.6% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-21 · updated 2026-07-30
• Weakness: CWE-400

Description

Netty is a network application framework for development of protocol servers and clients. In versions 4.2.0.Final through 4.2.15.Final and 4.1.0.Final through 4.1.135.Final, the `SpdyHttpDecoder` handler in Netty's SPDY-to-HTTP codec allocates a pooled `ByteBuf` when processing a client-initiated `SYN_STREAM` frame with `FLAG_FIN=0` and stores the partially constructed `FullHttpRequest` in `messageMap`; when the remote peer sends `RST_STREAM` for that stream or the accumulated content exceeds `maxContentLength`, the decoder removes the entry but does not release the pooled `ByteBuf`, causing native memory exhaustion. This issue is fixed in versions 4.1.136.Final and 4.2.16.Final.

Affected products

• netty: from 4.1.0 before 4.1.136; from 4.2.0 before 4.2.16 — fixed in 4.1.136, 4.2.16

How to fix

Upgrade to a fixed version: netty 4.1.136, 4.2.16. Check the vendor advisory for mitigations.

References

• https://github.com/netty/netty/commit/5b68c61f37aa4a3045cba624cbea239655c9003b
• https://github.com/netty/netty/commit/bb2ff68a1fb71cb4b0eb9a9e17b66c52aff680c6
• https://github.com/netty/netty/releases/tag/netty-4.1.136.Final
• https://github.com/netty/netty/releases/tag/netty-4.2.16.Final
• https://github.com/netty/netty/security/advisories/GHSA-jppx-w49h-x2qq

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