The QUIC transport parameters handler in s2n‑tls incorrectly allocates memory when processing a HelloRetryRequest, leaking the first allocation on the second call. This can lead to up to about 64 KB of unreclaimed memory per handshake, and the leaked memory accumulates over time on long‑running server processes. The vulnerability only affects TLS 1.3 QUIC traffic and does not impact non‑QUIC TLS connections. It therefore threatens the availability of QUIC‑enabled services by potentially exhausting available memory.

Amazon s2n‑tls, server‑side only, with QUIC enabled. No specific version information is specified in the CNA data, but the vendor advisory recommends updating to at least version v1.7.6 to fix the issue.

The CVSS score of 6.9 indicates a moderate severity vulnerability, while the EPSS score of less than 1% implies low likelihood of active exploitation. The vulnerability is not listed in the CISA KEV catalog. The likely attack vector is an unauthenticated network client that can deliberately send HelloRetryRequest messages to the server, amplifying the memory leak. An attacker could force many handshakes to cause the server to reach a memory capacity limit, leading to a denial of service. The documented exploit requires network access to the QUIC service and does not involve other prerequisites such as authentication or elevated privileges.