RUSTSEC-2026-0285: TLS 1.3 handshake messages incorrectly accepted across encryption level boundaries

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Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
65/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Active
Tech stack
rust
Domain
security

Research direction

Locate the repository's dependency declaration and resolved lockfile entry for rustls, then review how version 0.23.41 is selected. Update the dependency to patched version 0.23.45 or later and confirm the repository's existing checks pass without retaining the vulnerable version.

Written by the indexing model from the issue text.

Description

Details
Package rustls
Version 0.23.41
URL https://github.com/rustls/rustls/security/advisories/GHSA-2mjx-qc3c-rqvc
Patched Versions >=0.23.45
Unaffected Versions <0.23.13
Aliases GHSA-2mjx-qc3c-rqvc

Rustls accepted TLS 1.3 handshake messages sent at the wrong encryption level
when they followed a key-changing message in the same record. For example,
a plaintext EncryptedExtensions message packed into the same record as the
ServerHello was accepted.

RFC 8446 section 5.1 requires that handshake messages do not span key changes,
and that implementations terminate the connection with an "unexpected_message"
alert if they do.

The handshake transcript is still authenticated, so a network-position attacker
cannot use this to alter or complete a handshake; the practical effect is that
a peer could send handshake messages that should be encrypted in plaintext
without rustls rejecting the connection.

This is functionally the same bug as Go's
GO-2026-4340 (CVE-2025-61730).

Dominant language
Rust
Stars
142
Forks
99
PR merge metrics
No merged PRs in 30d

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

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