Bug 2514546

Summary: CVE-2026-29035 civetweb: CivetWeb: Arbitrary code execution via crafted WebSocket frames [epel-all]
Product: [Fedora] Fedora EPEL Reporter: Ganesh <gnaik>
Component: civetwebAssignee: Mattias Ellert <mattias.ellert>
Status: CLOSED NOTABUG QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: epel10CC: kkeithle, mattias.ellert
Target Milestone: ---Keywords: Security, SecurityTracking
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard: {"flaws": ["c5690dbf-c738-417b-8fae-dd38cc4ce6f9"]}
Fixed In Version: Doc Type: ---
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2026-08-28 05:40:13 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On:    
Bug Blocks: 2514388    

Description Ganesh 2026-08-12 10:15:22 UTC 
Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.

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.
Comment 1 Mattias Ellert 2026-08-28 05:40:13 UTC 
(In reply to Ganesh from comment #0)
> when both USE_ZLIB and MG_EXPERIMENTAL_INTERFACES are defined.

The EPEL build of civetweb defines USE_ZLIB but not MG_EXPERIMENTAL_INTERFACES.
It is therefore not affected by this CVE.