CVE-2026-34183

A flaw was found in OpenSSL's QUIC PATH_CHALLENGE handler. A remote attacker can exploit this vulnerability by flooding a QUIC client or server with specially crafted PATH_CHALLENGE frames. This leads to unbounded memory allocation within the local QUIC stack, as the system continuously allocates PATH_RESPONSE frames without them being acknowledged. The primary consequence is a Denial of Service (DoS), causing the affected application to terminate abnormally due to memory exhaustion.

A Moderate severity flaw exists in the QUIC PATH_CHALLENGE handler, allowing a remote attacker to exhaust heap memory of a QUIC client or server. By flooding the local QUIC stack with PATH_CHALLENGE frames, a malicious peer can trigger unbounded memory allocation, leading to a denial of service for applications utilizing the vulnerable QUIC implementation.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

To mitigate this vulnerability, apply UDP rate limiting at your network edge to throttle malicious traffic. If QUIC is not strictly required, disable the listener entirely and configure your application to use standard TLS over TCP. Additionally, enforce strict process memory limits using cgroups to prevent host-wide memory exhaustion during an attack.