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
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Amazon | s2n-tls | ≤ v1.7.5 | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP7 | aws-efs-utils | 3.3.4-150600.17.12.1 | SUSE-SU-2026:5101-1 |
| SLES 15 SP6 | aws-efs-utils | 3.3.4-150600.17.12.1 | SUSE-SU-2026:5101-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | aws-efs-utils | 3.2.0-1.1 | openSUSE-SU-2026:11492-1 |
| openSUSE Tumbleweed | s2n | 1.7.7-1.1 | openSUSE-SU-2026:11526-1 |
| openSUSE Leap 16.0 | s2n | 1.5.1-bp160.2.1 | openSUSE-SU-2026:21501-1 |
Advisories 4
- SUSE-SU-2026:5101-1 Security update for aws-efs-utils SUSE / openSUSE Security Updates · Nov 5, 2026
- openSUSE-SU-2026:11526-1 libs2n1-1.7.7-1.1 on GA media SUSE / openSUSE Security Updates · Aug 16, 2026
- openSUSE-SU-2026:11492-1 aws-efs-utils-3.2.0-1.1 on GA media SUSE / openSUSE Security Updates · Aug 12, 2026
- openSUSE-SU-2026:21501-1 Security update for s2n SUSE / openSUSE Security Updates · Jul 31, 2026
References
- https://github.com/aws/s2n-tls/releases/tag/v1.7.6 release-notes patch
- https://staging.prod.website.marketing.aws.dev/security/security-bulletins/2026-062-aws/ vendor-advisory
- https://github.com/aws/s2n-tls/security/advisories/GHSA-cr7x-863j-xrc7 release-notes