# CVE-2026-123613: Rustls 0.23.13 before 0.23.45 TLS 1.3 Handshake Encryption Level Bypass

Status: published. Published: 2026-11-08. Updated: 2026-11-08.

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.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://github.com/rustls/rustls/commit/5046bdf8a612b35a2c1a9e168054c1d5c65e7dd7

## Affected products and versions

- rustls / rustls (rustls): ≥ 0.23.13; < 0.23.45 (affected, semver); 0.23.45 (unaffected, semver). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 6.9 (medium); CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N; source: CNA: VulnCheck

- CVSS 3.1: 5.3 (medium); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N; source: CNA: VulnCheck

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-20

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/rustls/rustls/security/advisories/GHSA-2mjx-qc3c-rqvc (CNA: VulnCheck; vendor-advisory)

- https://github.com/rustls/rustls/commit/5046bdf8a612b35a2c1a9e168054c1d5c65e7dd7 (CNA: VulnCheck; patch)

- https://www.vulncheck.com/advisories/rustls-0.23.13-before-0.23.45-tls-1.3-handshake-encryption-level-bypass (CNA: VulnCheck; third-party-advisory)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-123613; retrieved 2026-11-08; source updated 2026-11-08

Revision: f8af4f0c5d665fe128f5ed7c2b67557e7e55911c08638d981156bc7f7acde4e4

Canonical: https://y2.dev/cve/CVE-2026-123613

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