CVE-2026-123611 json
rustls before 0.23.46 Key Exchange Downgrade via Unauthenticated ServerHello
published 28d ago modified 3d ago also EUVD-2026-119370 , GHSA-w44r-93j7-qv28 , RUSTSEC-2026-0349
- cvss
- 3.7
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.2%
- EPSS 0.2% chance of exploitation in 30 days, percentile 8%
- public exploits
- 0
- none known
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.
Patch / fix
- crates.io rustls 0.23.46, 0.24.0-dev.2
- rustls rustls 0.23.46
- github.com/rustls/rustls@8fa0dc5 commit
- github.com/rustls/rustls@f04804f commit
- github.com/rustls/rustls#3355 pull request
- github.com/rustls/rustls/releases/tag/v/0.23.46 release
Is CVE-2026-123611 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.
Check with FencerExploit prediction
0.19% chance of exploitation in the next 30 days, higher than 8% of all scored CVEs (FIRST EPSS, 2026-11-11).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 4.0 | 6.3 | 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 |
| CNA | 3.1 | 3.7 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N |
| GitHub | 3.1 | 3.7 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N |
| CNA | 4.0 | 6.3 | 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X |
| NVD | 3.1 | 3.7 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N |
| OSV | 3.1 | 3.7 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| crates.io | rustls | <0.23.46 >=0.24.0-dev.1, <0.24.0-dev.2 >=0.0.0-0, <0.23.46 |
0.23.46 0.24.0-dev.2 |
Affected products
- rustls rustls
Classification
- Weakness
-
- CWE-757 Selection of Less-Secure Algorithm During Negotiation
References
-
github.com
/rustls/rustls/pull/3355
web
-
github.com
/rustls/rustls/commit/8fa0dc5d517a63411ad1e528249bdf5b098ae5e4
web
-
github.com
/rustls/rustls/commit/f04804fa13341a9b1dc02b5d1dd8a746f2c4b7fb
web
-
github.com
/rustls/rustls/security/advisories/GHSA-w44r-93j7-qv28
vendor-advisory, web
-
vulncheck.com
/advisories/rustls-before-0.23.46-key-exchange-downgrade-via-unauthenticated-serverhello
third-party-advisory
-
github.com
/rustls/rustls
package
-
github.com
/rustls/rustls/releases/tag/v/0.23.46
web
-
rustsec.org
/advisories/RUSTSEC-2026-0349.html
web, advisory
-
crates.io
/crates/rustls
package
Sources
- CVE List CVE-2026-123611
- GitHub Advisory GHSA-w44r-93j7-qv28
- NVD CVE-2026-123611
- OSV RUSTSEC-2026-0349
Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.