CVE-2026-12707: Unbounded path event queue growth in quiche via peer-driven source connection ID rotation
Summary
Cloudflare quiche was discovered to be vulnerable to memory resource exhaustion due to unbounded queuing of post-handshake client migration events.
Impact
quiche supports the connection migration features described in Section 9 of RFC 9000, which allows a single QUIC connection to survive changes in the network path. Although quiche implements the protections described in Section 9.3 of RFC 9000 to limit server state commitment, it was discovered that the collection of PathEvents, intended to be consumed by applications via the patheventnext() function, was not bounded.
Once the QUIC handshake completed, a peer could exploit rapid source address migration in order to cause unbounded queuing of the PathEvent::ReusedSourceConnectionId type. Servers are vulnerable even if active connection migration is disabled.
Mitigation:
Applications can call patheventnext() to drain the PathEvent collection, mitigating the attack.
Users are requested to upgrade to quiche 0.29.3 which is the earliest version that prevents excessive queueing of PathEvent::ReusedSourceConnectionId.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
quicheto a version that resolves this vulnerability.Fixed in 0.29.3 - Compensating control
After the QUIC handshake completes, use path_event_next() to drain the PathEvent collection (mitigates unbounded queuing of PathEvent::ReusedSourceConnectionId).
Event History
Frequently Asked Questions
What is the severity of CVE-2026-12707?
The severity of CVE-2026-12707 is high, with a score of 7.5.
What is CVE-2026-12707 about?
CVE-2026-12707 involves unbounded path event queue growth in Cloudflare's quiche due to post-handshake client migration.
How do I fix CVE-2026-12707?
To fix CVE-2026-12707, update to the latest version of Cloudflare quiche where this vulnerability has been addressed.
What is the impact of CVE-2026-12707?
The impact of CVE-2026-12707 is memory resource exhaustion from unbounded queuing of connection migration events.
Which software is affected by CVE-2026-12707?
CVE-2026-12707 affects Cloudflare quiche.