What’s Vulnerable › Vulnerabilities
CVE-2026-59901: Netty Bzip2Decoder: Infinite Loop in RLE State Machine Leads to Event-Loop Thread Hang
- Severity: high (CVSS 7.5 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 0.5% probability of exploitation in the next 30 days
- Public exploit or detection template: none known
- Published: 2026-07-29 · updated 2026-08-06
- Weakness: CWE-835
Description
Netty is an asynchronous, event-driven network application framework. Prior to versions 4.1.136.Final and 4.2.16.Final, the `Bzip2Decoder` handler in Netty's compression codec pipeline is vulnerable to a denial-of-service attack through a malformed bzip2 stream that permanently captures the event-loop thread in an infinite loop. The vulnerability exists in the run-length encoding (RLE) state machine within [`Bzip2BlockDecompressor.read()`]. This issue has been fixed in versions 4.1.136.Final and 4.2.16.Final.
Affected products
- netty: 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
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