Bug 2514388 (CVE-2026-29035)

Summary: CVE-2026-29035 CivetWeb: CivetWeb: Arbitrary code execution via crafted WebSocket frames
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedKeywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in CivetWeb. An unauthenticated remote attacker could exploit a heap and stack buffer overflow vulnerability by sending specially crafted compressed WebSocket frames. This could lead to memory corruption, potentially resulting in denial of service or arbitrary code execution. The vulnerability occurs during the `permessage-deflate` decompression process when specific experimental interfaces are enabled.
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Bug Depends On: 2514545, 2514546, 2514547, 2514548    
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Description OSIDB Bzimport 2026-08-11 20:31:27 UTC 
CivetWeb (commit 4a4f0c95) contains a heap and stack buffer overflow vulnerability in the read_websocket() function that allows unauthenticated remote attackers to corrupt memory by sending compressed WebSocket frames when both USE_ZLIB and MG_EXPERIMENTAL_INTERFACES are defined. Attackers can negotiate permessage-deflate during the WebSocket handshake and send a crafted frame with the RSV1 bit set, causing the server to write a 4-byte zlib sync trailer out-of-bounds past the allocated buffer, leading to heap metadata corruption, denial of service, or potential code execution.