Bug 2504495 (CVE-2026-16318) - CVE-2026-16318 s2n-tls: s2n-tls: Denial of Service due to memory leak in QUIC transport parameters handler
Summary: CVE-2026-16318 s2n-tls: s2n-tls: Denial of Service due to memory leak in QUIC...
Keywords:
Status: NEW
Alias: CVE-2026-16318
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Product Security
QA Contact:
URL:
Whiteboard:
Depends On: 2506060
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-07-21 21:02 UTC by OSIDB Bzimport
Modified: 2026-07-22 11:07 UTC (History)
0 users

Fixed In Version:
Clone Of:
Environment:
Last Closed:
Embargoed:

Attachments (Terms of Use)

Description OSIDB Bzimport 2026-07-21 21:02:53 UTC 
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
Note You need to log in before you can comment on or make changes to this bug.