What is CVE-2026-123613?

CVE-2026-123613 is a medium-severity vulnerability in Rustls, classified under Improper Input Validation. CVSS score: 5.3/10. Published 2026-11-08.

How severe is CVE-2026-123613?

Medium severity. CVSS v3 base score is 5.3 out of 10.

Improper input validation in Rustls

CVE-2026-123613

Rustls from 0.23.13 before 0.23.45 accepts TLS 1.3 handshake messages at the wrong encryption level when they follow a key-changing message in the same record, because Deframer::aligned does not enforce RFC 8446 record-boundary alignment. A peer or on-path attacker can pack a plaintext EncryptedExtensions with the ServerHello, which rustls accepts unencrypted.

Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)

Published 2026-11-08.

CVSS v3 metric

CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N.

EPSS exploit prediction

No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.

Affected products

Rustls

Weakness classification (CWE)

CWE-20 — Improper Input Validation

References

github.com/rustls/rustls/commit/5046bdf8a612b35a2c1a9e168054c1d5c65e7dd7 (patch)
github.com/rustls/rustls/security/advisories/GHSA-2mjx-qc3c-rqvc (vendor-advisory)
www.vulncheck.com/advisories/rustls-0.23.13-before-0.23.45-tls-1.3-handshake-en… (third-party-advisory)

Frequently asked questions

What is CVE-2026-123613?: CVE-2026-123613 is a medium-severity vulnerability in Rustls, classified under Improper Input Validation. CVSS score: 5.3/10. Published 2026-11-08.
How severe is CVE-2026-123613?: Medium severity. CVSS v3 base score is 5.3 out of 10.