CVE-2026-123611

rustls before 0.23.46 Key Exchange Downgrade via Unauthenticated ServerHello

Published Nov 8, 2026 CVSS 4.0 · 6.3 Medium EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
First Time appeared Rustls
Rustls rustls
Vendors & Products Rustls
Rustls rustls
Type Values Removed Values Added
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.
Title rustls before 0.23.46 Key Exchange Downgrade via Unauthenticated ServerHello
First Time appeared Rustls Project
Rustls Project rustls
Weaknesses CWE-757
CPEs cpe:2.3:a:rustls_project:rustls:*:*:*:*:*:*:*:*
Vendors & Products Rustls Project
Rustls Project rustls
References
Metrics cvssV3_1

{'score': 3.7, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N'}

cvssV4_0

{'score': 6.3, 'vector': 'CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
VulnCheck
Published
Updated
Nov 13, 2026, 3:12 AM
Reserved
Nov 6, 2026, 1:02 AM
Status
Awaiting Analysis
Published
Nov 8, 2026, 2:16 AM
Modified
Nov 13, 2026, 4:17 AM