# CVE-2026-15711: GNOME libsoup denial of service via oversized WebSocket control frame

Source: https://junglewise.ai/threats/cve-2026-15711-gnome-libsoup-denial-of-service-via-oversized-websocket-control  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-14. Updated: 2026-07-14  
License: CC BY 4.0 with a link back

CVE-2026-15711 · Severity: high · CVSS 7.5 · Published 2026-07-14

libsoup, a widely used HTTP client/server library for GNOME and Linux applications, contains a flaw in how it handles WebSocket communications. An attacker can send a specially crafted message that violates standard networking rules, causing the application using libsoup to crash or immediately terminate the connection. This results in a denial of service, potentially disrupting web services or applications that rely on real-time WebSocket data.

Technologies: [Gnome Libsoup](https://junglewise.ai/threats/technologies/libsoup). Vendors: [Gnome](https://junglewise.ai/threats/vendors/gnome).

## Quick answers

**Is CVE-2026-15711 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-15711 being exploited in the wild.

**How severe is CVE-2026-15711?** High severity, with a CVSS score of 7.5, published 14 July 2026.

**Which products and versions are affected?** Gnome Libsoup Red Hat Enterprise Linux 10.

**Is there a fix for CVE-2026-15711?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-15711 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-15711?** Check whether you run Gnome Libsoup at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A vulnerability exists in libsoup's WebSocket frame parsing implementation within `soup-websocket-connection.c`. Per RFC 6455 §5.5, control frames (PING, PONG, CLOSE) must not exceed a payload of 125 bytes. While libsoup's send path correctly enforces this limit, the receive path (`process_frame()`) fails to validate incoming control frame lengths. When an oversized PING is received, the library attempts to echo it back; the send path then detects the violation and triggers `protocol_error_and_close()` on itself. This allows a remote, unauthenticated attacker to cause a connection crash or application-level denial of service with a single non-compliant frame.

## Affected products

- Red Hat libsoup3 Red Hat Enterprise Linux 10
- Red Hat libsoup Red Hat Enterprise Linux 8, 9
- GNOME libsoup 3.4.4, likely all versions with WebSocket support

## Timeline

- 2026-07-14: disclosed: Publicly reported via GNOME GitLab and Red Hat Bugzilla
- 2026-07-14: advisory: NVD published the CVE record

## References

- [https://access.redhat.com/downloads/content/package-browser/](https://access.redhat.com/downloads/content/package-browser/)
- [https://access.redhat.com/security/cve/CVE-2026-15711](https://access.redhat.com/security/cve/CVE-2026-15711)
- [https://bugzilla.redhat.com/show_bug.cgi?id=2499924](https://bugzilla.redhat.com/show_bug.cgi?id=2499924)
- [https://gitlab.gnome.org/GNOME/libsoup/-/issues/515](https://gitlab.gnome.org/GNOME/libsoup/-/issues/515)

## Related threats

- [libsoup HTTP request smuggling via undrained Expect: 100-continue body](https://junglewise.ai/threats/cve-2026-103399-a-flaw-was-found-in-soupserver-libsoup-when-an-http-1-x-client)
- [libsoup heap buffer overflow in permessage-deflate WebSocket extension](https://junglewise.ai/threats/cve-2026-102560-a-flaw-was-found-in-libsoup-when-the-permessage-deflate)
- [libsoup heap buffer overflow in WebSocket handling](https://junglewise.ai/threats/cve-2026-102558-a-flaw-was-found-in-libsoup-when-max-incoming-payload-size-is)
- [libsoup out-of-bounds read in data-URI base64 decoding](https://junglewise.ai/threats/cve-2026-102555-a-flaw-was-found-in-libsoup-the-soup-uri-decode-data-uri)
- [libsoup heap corruption in WebSocket message reassembly](https://junglewise.ai/threats/cve-2026-102557-a-flaw-was-found-in-libsoup-when-reassembling-fragmented)