CVE-2026-12707 Unbounded path event queue growth in quiche via peer-driven source connection ID rotation
A remote attacker can cause memory exhaustion in Cloudflare quiche by triggering unbounded path event queue growth via rapid connection migration.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-12707?
CVE-2026-12707 is a high-severity denial of service vulnerability in Cloudflare quiche, published on 14 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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 path_event_next() 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 path_event_next() 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.
Weakness: CWE-770
Which versions are affected by CVE-2026-12707?
How do I fix CVE-2026-12707?
No fix has been published for CVE-2026-12707 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-12707 being exploited?
There is no known exploitation of CVE-2026-12707 in the wild and no public exploit code.
Sources
Also known as GHSA-4q5x-gp38-rfp4.