webrtcbin accepts remote SDP without a=fingerprint due to inverted presence check

Summary

A logic vulnerability was found in GStreamer's webrtcbin component. The _check_sdp_crypto() function contains an inverted boolean condition that causes it to accept remote SDP offers or answers that lack the required a=fingerprint attribute, while incorrectly rejecting those that include it. An attacker with the ability to intercept and modify WebRTC signaling messages could exploit this to bypass the SDP-level DTLS certificate fingerprint binding, weakening defenses against man-in-the-middle attacks on media streams. This vulnerability is rated as Low severity because exploitation requires man-in-the-middle access to the WebRTC signaling channel, which is typically TLS-protected. Additionally, the DTLS layer may still independently validate certificates, limiting the practical impact of this bypass. The webrtcbin component is shipped as part of gstreamer1-plugins-bad-free in Red Hat Enterprise Linux 8, 9, 10, and RHIVOS. The vulnerability weakens one layer of defense-in-depth but does not constitute a complete cryptographic break. Red Hat severity: Low — CVSS 3.7 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N). Weakness: CWE-670. Affected Red Hat products: Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 6; Red Hat Enterprise Linux 7; Red Hat Enterprise Linux 8; Red Hat Enterprise Linux 9. Red Hat does not currently list a fixing RHSA for this CVE.