Bug 2499924 (CVE-2026-15711)

Summary: CVE-2026-15711 libsoup: SoupWebsocketConnection: libsoup: WebSocket remote denial of service via oversized control frame protocol violation
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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A vulnerability was found in libsoup's WebSocket frame parsing implementation. The library fails to validate length rules specified in RFC 6455 §5.5, which mandates that all WebSocket control frames (e.g., PING, PONG, CLOSE) contain a payload of 125 bytes or less. A remote, unauthenticated attacker can exploit this by sending a non-compliant, oversized control frame. Because the parser handles this protocol violation improperly instead of throwing an immediate connection termination error, it triggers a internal processing crash, resulting in a remote denial of service (DoS) for applications utilizing libsoup WebSockets.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Bug Depends On: 2500545, 2500546, 2500547    
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Description OSIDB Bzimport 2026-07-14 09:53:23 UTC 
**Vulnerability Reference:**

A flaw in libsoup's WebSocket implementation allows a remote attacker to trigger a denial of service (DoS) by exploiting a protocol validation failure.

**Component / Vulnerable Part:**

`libsoup` -> `libsoup/websocket/soup-websocket-connection.c` (Control frame parser)

**Technical Analysis & Root Cause:**

Per RFC 6455 §5.5, WebSocket control frames (PING, PONG, CLOSE) must not exceed a payload length of 125 bytes and cannot be fragmented. libsoup's frame parsing logic fails to immediately reject non-compliant control frames exceeding this limit. When an oversized control frame is received, the unexpected state disrupts the state machine or triggers an unhandled execution error, forcing the library to abruptly crash.

**Impact:**

A remote, unauthenticated attacker (client or server) can send a single malformed, oversized control frame to instantly terminate the connection wrapper, resulting in a remote denial of service for any application using libsoup WebSockets.