CVE-2026-94450 AWS CVE debrief

Who should care

Defenders responsible for s2n-quic deployments, particularly those using server endpoints configured to send Retry packets, should assess exposure and prioritize remediation to prevent potential denial of service.

Why it matters

CVE-2026-94450 is a high-severity vulnerability in s2n-quic 1.88.0 and earlier, allowing an unauthenticated remote user to cause a denial of service. Defenders should assess exposure, prioritize remediation, and verify affected deployments.

• Denial of service via crafted UDP datagrams
• Potential disruption to server endpoints configured to send Retry packets
• Need for verification of affected deployments and remediation status

Technical summary

The vulnerability is caused by improper validation of the Destination Connection ID length in s2n-quic 1.88.0 and earlier. This allows 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. The issue can be remediated by upgrading to version v1.89.0 or later. Affected deployments should be verified, and defenders should assess exposure and prioritize remediation to prevent potential denial of service.

Defensive priority

Upgrade to v1.89.0 or later to prevent denial of service via crafted UDP datagrams.

Recommended defensive actions

• Upgrade to s2n-quic version v1.89.0 or later
• Review server endpoint configurations to ensure only necessary endpoints send Retry packets
• Monitor for crafted UDP datagrams in network traffic
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up
• Review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance
• Plan vendor-supported updates or mitigations through normal change control where exposure is confirmed
• Check relevant monitoring, detection, and logs for exposed assets that need extra review

Evidence notes

The CVE record and NVD entry provide details on the vulnerability, its impact, and remediation steps. However, the exact scope of affected deployments and potential compensating controls require further verification.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.