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National Vulnerability Database

National Vulnerability Database

NVD

National Vulnerability Database
  1. Vulnerabilities

CVE-2026-16318 Detail

Description

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


Metrics

 
NVD enrichment efforts reference publicly available information to associate vector strings. CVSS information contributed by other sources is also displayed.
CVSS 4.0 Severity and Vector Strings:

NIST CVSS score
NIST: NVD
N/A
NVD assessment not yet provided.

Nist CVSS score does not match with CNA score
CNA:  AMZN
CVSS-B 6.9 MEDIUM
Vector:  CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

References to Advisories, Solutions, and Tools

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URL Source(s) Tag(s)
https://github.com/aws/s2n-tls/releases/tag/v1.7.6 AMZN
https://github.com/aws/s2n-tls/security/advisories/GHSA-cr7x-863j-xrc7 AMZN
https://staging.prod.website.marketing.aws.dev/security/security-bulletins/2026-062-aws/ AMZN

Weakness Enumeration

CWE-ID CWE Name Source
CWE-401 Missing Release of Memory after Effective Lifetime AMZN  

Change History

1 change records found show changes

Quick Info

CVE Dictionary Entry:
CVE-2026-16318
NVD Published Date:
07/21/2026
NVD Last Modified:
07/21/2026
Source:
AMZN