Executive brief
s2n-tls is an open-source implementation of the TLS/SSL protocols used to secure network communications. A memory leak vulnerability exists in server-side deployments that have QUIC enabled, which could allow a remote attacker to repeatedly trigger specific connection requests to exhaust the server's available memory. If left unaddressed, this could eventually lead to service instability or crashes, requiring a process restart to recover.
Technical details
A memory leak (CWE-401) exists in s2n-tls when handling QUIC transport parameters during a TLS 1.3 HelloRetryRequest (HRR). The vulnerability is caused by the incorrect use of 's2n_alloc' instead of 's2n_realloc' in the extension handler; when an HRR occurs, the handler is invoked a second time, causing 's2n_alloc' to zero the existing pointer and leak the previously allocated memory. An unauthenticated remote attacker can deliberately force HRRs to leak approximately 64 KB of memory per handshake. This affects only server-side, QUIC-enabled deployments. The issue is resolved in version v1.7.6.
Affected products
- Amazon s2n-tls <= v1.7.5
Timeline
- 2026-07-21: advisory: GitHub Advisory GHSA-cr7x-863j-xrc7 published
- 2026-07-21: patched: s2n-tls version v1.7.6 released