CVE-2026-16318
Amazon / Amazon.com, Inc. · published 2026-07-21
Source record Collected from the National Vulnerability Database (NVD)
Description
Description by AMZN via the CVE Program.
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
Filed by AMZN; not a statement by Amazon / Amazon.com, Inc..
Status at the source
- NVD status: Awaiting Analysis — NVD has not analysed this CVE.
Affected products, as the source lists them
| Vendor | Product | Versions |
|---|---|---|
| Amazon | s2n-tls | 0 – v1.7.5 and earlier: affected |
DeSpy has not checked any unit, hardware revision or firmware. A product missing here is not a statement that it is unaffected.
Scores, as their sources published them
- CVSS 4.0: 6.9 MEDIUM — as published by AMZN (Secondary)
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - CVSS 3.1: 5.3 MEDIUM — as published by AMZN (Secondary)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L - SSVC — CISA's assessment (SSVC 2.0.3, CISA Coordinator): Exploitation: none · Automatable: yes · Technical impact: partial
DeSpy does not score records. These are the sources' own values.
Weaknesses
Sources
References the source lists
- https://github.com/aws/s2n-tls/releases/tag/v1.7.6
- https://github.com/aws/s2n-tls/security/advisories/GHSA-cr7x-863j-xrc7
- https://staging.prod.website.marketing.aws.dev/security/security-bulletins/2026-062-aws/
Source dates: published 2026-07-21, last changed 2026-07-22. DeSpy's copy of this version is dated 2026-09-28.
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