Description
rustls before 0.23.46 contains a key exchange downgrade vulnerability that allows network attackers to poison the per-server-name key-exchange group record via an unauthenticated ServerHello. Attackers can answer one connection with a ServerHello selecting X25519, causing later ClientHellos to send only classical shares and lose post-quantum confidentiality.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| rustls | rustls | < 0.23.46 | 0.23.46 |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | rust-rustls | No fix yet | — |
| Debian 13 | rust-rustls | No fix yet | — |
| Debian 12 | rust-rustls | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | rust-rustls | No fix yet | — |
| Ubuntu 26.04 LTS | rust-rustls | No fix yet | — |
| Ubuntu 24.04 LTS | rust-rustls | No fix yet | — |
Azure Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Azure Linux 3 | rust +4 | No fix yet | — |
Affected packages
| Ecosystem | Package | Affected | Fixed | Record |
|---|---|---|---|---|
| crates.io | rustls | < 0.23.46 | 0.23.46 | GHSA-w44r-93j7-qv28 |
| crates.io | rustls | >= 0.24.0-dev.1, < 0.24.0-dev.2 | 0.24.0-dev.2 | GHSA-w44r-93j7-qv28 |
| crates.io | rustls | >= 0.0.0-0, < 0.23.46 | 0.23.46 | RUSTSEC-2026-0349 |
References
- GitHub Security Advisory (GHSA-w44r-93j7-qv28) vendor-advisory
- VulnCheck Advisory: rustls before 0.23.46 Key Exchange Downgrade via Unauthenticated ServerHello third-party-advisory