CVE-2026-12707 in quiche
Summary
by MITRE • 07/14/2026
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:
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Applications can call path_event_next() to drain the PathEvent collection, mitigating the attack.
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Users are requested to upgrade to quiche 0.29.3 which is the earliest version that prevents excessive queueing of PathEvent::ReusedSourceConnectionId.
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Analysis
by VulDB Data Team • 07/14/2026
The vulnerability in Cloudflare's quiche library represents a critical memory resource exhaustion issue stemming from unbounded queuing of post-handshake client migration events. This flaw specifically targets the implementation of QUIC connection migration features as defined in RFC 9000, where the protocol supports maintaining connections across network path changes through mechanisms described in Section 9. While quiche appropriately implements protections outlined in Section 9.3 to limit server state commitment, it fails to constrain the collection of PathEvents that applications access via the path_event_next() function. The vulnerability manifests when a peer exploits rapid source address migration following QUIC handshake completion, leading to unlimited queuing of PathEvent::ReusedSourceConnectionId entries.
The technical nature of this flaw aligns with CWE-770, which describes allocation of resources without limits or throttling, and represents a classic example of memory exhaustion through unbounded data structures. The attack vector operates regardless of whether active connection migration is enabled on the server side, making it particularly concerning as it affects all quiche implementations. This vulnerability falls under the ATT&CK technique T1499.001 for Resource Exhaustion and T1566.002 for Phishing with Malicious Attachments, though the specific exploitation occurs through protocol-level manipulation rather than traditional phishing vectors.
The operational impact of this vulnerability extends beyond simple memory consumption, as it can lead to complete service disruption on affected servers. When PathEvent collections grow unchecked, they consume increasing amounts of system memory until the server becomes unresponsive or crashes entirely. The issue affects both client and server implementations since the problematic queuing occurs regardless of migration state configuration. Applications using quiche libraries become susceptible to denial-of-service conditions where malicious actors can systematically exhaust available memory resources through repeated source address migration attempts, particularly targeting the PathEvent::ReusedSourceConnectionId type which accumulates without bounds.
Mitigation strategies focus on two primary approaches that address both immediate remediation and long-term prevention. The first approach requires applications to actively drain PathEvent collections by calling path_event_next() regularly, preventing accumulation of events in memory. This defensive programming practice aligns with secure coding principles from the CERT Secure Coding Standards and helps maintain predictable resource usage patterns. The second and more comprehensive mitigation involves upgrading to quiche version 0.29.3 or later, which specifically addresses the excessive queueing behavior by implementing proper bounds on PathEvent::ReusedSourceConnectionId entries. This upgrade resolves the root cause rather than merely addressing symptoms, providing a permanent solution that prevents the unbounded queuing from occurring in the first place. Organizations should prioritize this upgrade as it represents the most effective means of protecting against potential exploitation while maintaining full protocol compliance with RFC 9000 requirements.