rustls before 0.23.46 Key Exchange Downgrade via Unauthenticated ServerHello
- Exploited
- No known exploitation
- Fix
- Fixed in 0.23.46
- Who is exposed
- Not reported
Do first: Upgrade to a fixed version: 0.23.46.
- Published
- Last modified
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 23/100 · provisional
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
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.
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure17/25No login or user action needed per the CVSS vector, reachable over the network without a login · Unknown: No advisory context yet
- Reach?/20Unknown. No tracked technology or package matched
- Severity6.3/10CVSS 6.3
- No patch0/5No signal
What would change the score
- Would score about 68 if added to CISA KEV
- Would score about 63 if CISA's SSVC rates exploitation active
- Would score about 28 if advisories confirm default setups are exposed
What to do
Upgrade to a fixed version: 0.23.46.
Timeline
- CVE published
- First seen by cve.now
Affected versions
- rustls rustls
fixed in 0.23.46
Evidence 2
- Advisory
- Link
Corrections
None so far.
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Questions about CVE-2026-123611
Is CVE-2026-123611 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data
Which versions are affected by CVE-2026-123611?
rustls: before 0.23.46.Source: cve.now feed data
How do I fix CVE-2026-123611?
Upgrade to a fixed version: 0.23.46.Source: cve.now feed data