CVSS 4.0
6.3 mediumCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:NCVE-2026-123611
Medium (6.3) in rustls rustls. EPSS 0.2% estimated probability of exploitation activity in the next 30 days. Fixed in rustls 0.23.46, 0.24.0-dev.2.
On this page
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.
Severity
CVSS 3.1
3.7 lowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N- EPSS
- 0.2% estimated probability of exploitation activity in the next 30 days; 9th percentile. Scored 2026-11-10. A forecast for this CVE across the internet, not for your own systems.
- CWE
- CWE-757 Selection of Less-Secure Algorithm During Negotiation (Algorithm Downgrade)
- OWASP Top 10
- A04:2025 Cryptographic Failures
- Published
- NVD analysis
- Awaiting analysis
- Record from
- the NVD, synced
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Affected
Versions
From the CNA's record in the CVE List.
| Product | Affected |
|---|---|
| rustls | before 0.23.46 |
Packages (OSV)
| Advisory | Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|---|
| GHSA-w44r-93j7-qv28 | 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 |
| RUSTSEC-2026-0349 | crates.io | rustls | >=0.0.0-0 <0.23.46 | 0.23.46 |
Linux distributions
| Distribution | Release | Package | Fixed in | Advisory |
|---|---|---|---|---|
| Debian | 12, 13, 14 | rust-rustls | no fix listed | DEBIAN-CVE-2026-123611 |
| Ubuntu | 24.04:LTS, 26.04:LTS, 26.10 | rust-rustls | no fix listed | UBUNTU-CVE-2026-123611 |
From the distributions' data via OSV.dev: the Debian Security Tracker; Ubuntu Security Notices © Canonical Ltd., CC BY-SA 4.0. Modified: reformatted and linked to CVE records. Credits. On the distributions' own pages: Debian · Ubuntu.
Attack patterns (CAPEC)
- CAPEC-220 Client-Server Protocol Manipulation Severity: Medium
- CAPEC-606 Weakening of Cellular Encryption Severity: High
- CAPEC-620 Drop Encryption Level Severity: High
The attack patterns MITRE's CAPEC relates to this record's weaknesses, as MITRE names them. Credits.