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Vulnerabilities

Vulnerability · GHSA-2mjx-qc3c-rqvc

Rustls: TLS 1.3 handshake messages incorrectly accepted across encryption level boundaries

Published Oct 5, 2026 · catalog updated Oct 27, 2026 · Rustls: TLS 1.3 handshake

Last checked Oct 28, 2026. A connected source was read within the last 7 days.

Open the advisory

Exploitation likelihood is not on this record for GHSA-2mjx-qc3c-rqvc. A missing EPSS score is not a low risk. Compare Rustls: TLS 1.3 handshake with the linked advisory before you change production.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (Rustls: TLS 1.3 handshake).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
  • EPSS is missing. A missing score is not a low risk.
Severity
Medium5.3
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
Awaiting synchronization with FIRST
Remediation
Advisory link
Affected products
crates.io rustls

Rustls accepted TLS 1.3 handshake messages sent at the wrong encryption level when they followed a key-changing message in the same record. 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 issue affects rustls versions 0.23.13 through 0.23.44 inclusive. # Original report ### Summary Rustls (tested version 0.23.44, and it appears still an issue on latest master though I have not tested this) accepts a TLS 1.3 server flight where a plaintext EncryptedExtensions is packed into the same record as the ServerHello. This is very similar to Go's CVE-2025-61730 fixed in https://github.com/golang/go/commit/5046bdf8a612b35a2c1a9e168054c1d5c65e7dd7 ### Details It appears considers itself aligned as long as all messages remaining in the buffer are complete. Rustls processes the ServerHello, installs the handshake keys, then pulls the complete (plaintext) EncryptedExtensions out of the buffer. This is insufficient per RFC 8446 section 5.1's > Handshake messages MUST NOT span key changes. Implementations MUST verify that all messages immediately preceding a key change align with a record boundary; if not, then they MUST terminate the connection with an "unexpected_message" alert. Because the ClientHello, EndOfEarlyData, ServerHello, Finished, and KeyUpdate messages can immediately precede a key change, implementations MUST send these messages in alignment with a record boundary. ### Impact An on path attacker can inject plaintext messages that are accepted. ### Tool Use Disclosure This was discovered by a new TLS/DTLS test suite currently under construction. The specific testcase was inspired by the Go CVE. Other tested implementations (Botan, OpenSSL, BoringSSL, Go, wolfSSL) reject this protocol flow. Daybreak Blue reviewed the rustls code to identify p

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • crates.io rustls0.23.13 → 0.23.45

How to fix GHSA-2mjx-qc3c-rqvc

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

Exploitation likelihood is not on this record for GHSA-2mjx-qc3c-rqvc. A missing EPSS score is not a low risk. Compare Rustls: TLS 1.3 handshake with the linked advisory before you change production.

Which versions are affected?

Compare what you have installed with 0.23.13 → 0.23.45. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

No weakness class is stored. EPSS is not on this record yet. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Oct 5, 2026 · GitHub Advisory Database

    Detected

    Rustls accepted TLS 1.3 handshake messages sent at the wrong encryption level when they followed a key-changing message in the same record. 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 t

  2. Oct 27, 2026 · GitHub Advisory Database

    Fix available

    rustls fixed in 0.23.45

  3. Oct 27, 2026 · GitHub Advisory Database

    Fix available

    rustls fixed in 0.23.45

  4. Oct 27, 2026 · GitHub Advisory Database

    Updated

    Rustls accepted TLS 1.3 handshake messages sent at the wrong encryption level when they followed a key-changing message in the same record. 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 t

Sources

References

Freshness

Last verified in this catalog Oct 27, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • GitHub Advisory DatabaseOct 28, 2026
  • OpenSSF OSV / OSV ScannerOct 28, 2026