CVE-2026-123611
rustls before 0.23.46 Key Exchange Downgrade via Unauthenticated ServerHello
CVSS Score
3.7
EPSS Score
0.0%
EPSS Percentile
0th
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.
| CWE | CWE-757 |
| Vendor | rustls |
| Product | rustls |
| Published | Nov 8, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
None
Affected Versions
rustls / rustls
0 < 0.23.46
References
Credits
🔍 Adam010341