CVE-2026-59901

Netty Bzip2Decoder: Infinite Loop in RLE State Machine Leads to Event-Loop Thread Hang

Published Jul 29, 2026 CVSS 4.0 · 8.7 High EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-558v-64gr-wgg4 Netty: [Bzip2Decoder] Infinite Loop in RLE State Machine Leads to Event-Loop Thread Hang
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description A flaw was found in the netty-codec-compression component of Netty. This vulnerability, caused by a logic error in the bzip2 decoder, allows a remote attacker to send specially crafted bzip2-compressed data. Processing this malformed data can trigger an infinite loop, causing the decoder thread to consume excessive CPU resources. This leads to a denial of service (DoS), requiring manual intervention to restore service. 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.
Title io.netty/netty-codec-compression: Netty: Infinite loop in netty-codec-compression (bzip2) Netty Bzip2Decoder: Infinite Loop in RLE State Machine Leads to Event-Loop Thread Hang
References
Metrics cvssV4_0

{'score': 8.7, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N'}

Type Values Removed Values Added
Description A flaw was found in the netty-codec-compression component of Netty. This vulnerability, caused by a logic error in the bzip2 decoder, allows a remote attacker to send specially crafted bzip2-compressed data. Processing this malformed data can trigger an infinite loop, causing the decoder thread to consume excessive CPU resources. This leads to a denial of service (DoS), requiring manual intervention to restore service.
Title io.netty/netty-codec-compression: Netty: Infinite loop in netty-codec-compression (bzip2)
Weaknesses CWE-835
References
Metrics threat_severity

None

cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

threat_severity

Important

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Jul 29, 2026, 6:09 PM
Reserved
Jul 7, 2026, 4:40 PM
Status
Analyzed
Published
Jul 29, 2026, 6:16 PM
Modified
Aug 6, 2026, 8:29 PM
Severity
Important
Public date
Jul 9, 2026, 12:00 AM