CVE-2026-12478: Libsoup: incomplete fix for cve-2026-0716: out-of-bounds read in libsoup websocket frame processing (unmasked path)
https://gitlab.gnome.org/GNOME/libsoup/-/workitems/476#note2695744
Other sources
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 UINT64MAX to trigger an OOB read in a libsoup-based client when maxincomingpayloadsize is set to 0.
— NVD
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
libsoupto a version that resolves this vulnerability.Fixed in 3.6.6Patch CVE-2026-0716 - Compensating control
If the libsoup-based client must accept WebSocket traffic from untrusted sources and max_incoming_payload_size can be set to 0, avoid setting max_incoming_payload_size=0 (set it to a non-zero limit) to prevent triggering the out-of-bounds read condition described for unmasked frames with payload length near UINT64_MAX.
Event History
Frequently Asked Questions
What is the severity of CVE-2026-12478?
CVE-2026-12478 has a medium severity score of 4.8.
How do I fix CVE-2026-12478?
To fix CVE-2026-12478, update to the latest version of Libsoup that addresses this vulnerability.
What types of attacks does CVE-2026-12478 allow?
CVE-2026-12478 may allow for out-of-bounds read attacks via unmasked server-to-client WebSocket frames.
What software is affected by CVE-2026-12478?
CVE-2026-12478 affects the Gnome libsoup software.
Is CVE-2026-12478 a complete fix for CVE-2026-0716?
No, CVE-2026-12478 is an incomplete fix for CVE-2026-0716, as it does not fully protect against all unmasked frames.