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TI-2026-13638 Aliases CVE-2026-16318

QUIC Transport Parameters Memory Leak During HelloRetryRequest in s2n-tls

Priority LOW 37CWE-401Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Attack requirements
None
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · Low
Fix status
No fix listed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-401.

Summary

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

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00388 33rd percentileScored 2026-11-07
Fix No fix listed No fixed version in the sources yet

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
AWSs2n-tlsup to v1.7.5—No fix listedCNA
  • s2n-tls VendorAWS Affected up to v1.7.5 Fixed in — No fix listed CNA

Remediation

No fixed version listed by the sources yet.

Vendor assessments

Red Hat

Red Hat's page for this CVE →

Not affected: 1 product
  • Red Hat

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-16318

References

Patch 1

Advisory 1

Other 1

  • TI-2026-23989 crypto: algif_aead - Revert to operating out-of-place KEVCVSS 3.1HIGH 7.8
  • TI-2023-23979 The HTTP/2 protocol allows a denial of service (server resource consumption) because… KEVCVSS 3.1HIGH 7.5
  • TI-2024-18648 Amazon AWS Amplify CLI before 12.10.1 incorrectly configures the role trust policy of IAM… CVSS 3.1CRITICAL 9.8
  • TI-2024-05929 Openssh: regresshion - race condition in ssh allows rce/dos CVSS 3.1HIGH 8.1
  • TI-2025-03847 Input validation issue in AWS Amplify Studio UI component properties CVSS 4.0CRITICAL 9.0
  • TI-2026-11603 HTTP/2 Stream Parser Confusion Body-Inspection Bypass in Amazon CloudFront with AWS WAF CVSS 4.0HIGH 7.9
See all 383 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences