Bug 2506060

Summary: CVE-2026-16318 s2n-tls: s2n-tls: Denial of Service due to memory leak in QUIC transport parameters handler [epel-all]
Product: [Fedora] Fedora EPEL Reporter: TEJ RATHI <trathi>
Component: s2n-tlsAssignee: Orphan Owner <extras-orphan>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: epel10CC: cloud-sig, davdunc, extras-orphan, nicola
Target Milestone: ---Keywords: Security, SecurityTracking
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Hardware: Unspecified   
OS: Unspecified   
Whiteboard: {"flaws": ["915fdb46-fe65-4ecb-9c02-6929e67a8485"]}
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Bug Depends On:    
Bug Blocks: 2504495    

Description TEJ RATHI 2026-07-22 11:07:25 UTC 
Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.

The QUIC transport parameters extension handler in s2n-tls incorrectly uses s2n_alloc instead of s2n_realloc to store the peer's transport parameters. When a TLS 1.3 connection goes through a HelloRetryRequest, the handler is called twice on the same connection. On the second call, s2n_alloc zeroes the existing pointer before allocating new memory, causing the first allocation to be leaked.



This can occur during normal QUIC traffic when a client offers a key share group the server does not prefer. An unauthenticated user can amplify the issue by deliberately forcing HelloRetryRequests, causing up to approximately 64 KB of unreachable memory per handshake. Over time, this can lead to increased memory consumption on long-running server processes. The unreachable memory is only reclaimed when the process is restarted.



Only server-side QUIC-enabled deployments are affected. Non-QUIC TLS connections are not affected.



We recommend you upgrade s2n-tls to version v1.7.6