CVE-2026-94450: Potential denial of service when configured to send Retry packets in s2n-quic

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.9% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-22 · updated 2026-10-20
Weakness: CWE-617

Description

Improper validation of the Destination Connection ID length in s2n-quic 1.88.0 and earlier may allow an unauthenticated remote user to cause a denial of service by shutting down a server endpoint via a single crafted UDP datagram. Only server endpoints specifically configured to send Retry packets are affected. To remediate this issue, users should upgrade to version v1.89.0 or later.

Affected products

AWS s2n-quic: through 1.88.0

References

https://aws.amazon.com/security/security-bulletins/2026-116-aws/
https://github.com/aws/s2n-quic/releases/tag/v1.89.0
https://github.com/aws/s2n-quic/security/advisories/GHSA-5rw2-6x5m-v22x

Get alerted when CVE-2026-94450 or the next vulnerability affects your stack