CVE-2026-102560

A flaw was found in libsoup. When the permessage-deflate WebSocket extension compresses a very large outgoing message, truncated size calculations used for GByteArray growth could wrap, causing zlib to write past the allocated buffer and resulting in a heap buffer overflow.

This issue is rated Important. Exploitation requires the permessage-deflate extension to be negotiated and a very large outgoing message to be compressed. Applications that enable WebSocket deflate with untrusted or unbounded message sizes are affected. Impact is heap corruption or denial of service.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

To mitigate this disable the permessage-deflate WebSocket extension if it is not required, and cap outgoing message sizes.