CVE-2026-12478

The fix for CVE-2026-0716 (commit 6ff7ef0, libsoup 3.6.6) placed the integer overflow guard inside the if (masked) block, leaving unmasked server-to-client frames unprotected. A malicious WebSocket server can send a crafted unmasked frame with a payload length near UINT64_MAX to trigger an OOB read in a libsoup-based client when max_incoming_payload_size is set to 0.

This vulnerability is rated Moderate for Red Hat because it requires a non-default configuration where max_incoming_payload_size is explicitly set to 0 or unset in libsoup's WebSocket frame processing. In typical Red Hat deployments, this configuration is not enabled by default, limiting the exposure to memory disclosure or application instability.

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 issue, applications utilizing libsoup's WebSocket support should ensure that the max_incoming_payload_size is explicitly set to a non-zero value. This prevents the library from processing WebSocket frames with an unset or zero maximum payload size, which can lead to out-of-bounds reads. Consult application-specific documentation for configuring libsoup parameters.