Selection of Less-Secure Algorithm During Negotiation ('Algorithm Downgrade') Affecting rust-rustls package, versions *


Severity

Recommended
0.0
low
0
10

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Threat Intelligence

EPSS
0.19% (9th percentile)

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  • Snyk IDSNYK-DEBIAN14-RUSTRUSTLS-22345976
  • published8 Nov 2026
  • disclosed8 Nov 2026

Introduced: 8 Nov 2026

NewCVE-2026-123611  (opens in a new tab)
CWE-757  (opens in a new tab)

How to fix?

There is no fixed version for Debian:14 rust-rustls.

NVD Description

Note: Versions mentioned in the description apply only to the upstream rust-rustls package and not the rust-rustls package as distributed by Debian. See How to fix? for Debian:14 relevant fixed versions and status.

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.

CVSS Base Scores

version 3.1