Vulnerability in Rustls
CVE-2026-123609
Rustls before 0.23.46 and 0.24.0-dev.1 before 0.24.0-dev.2 contains an information disclosure vulnerability where derived Debug formatting of client session values exposes secret key material. Custom ClientSessionStore implementations that log Tls12ClientSessionValue or Tls13ClientSessionValue can leak TLS 1.2 master secrets or TLS 1.3 resumption PSKs to log readers.
Published .
CVSS v3 metric
CVSS v3 base score 4.0 (Medium). Vector: CVSS:3.1/AV:L/AC:H/PR:H/UI:R/S:U/C:H/I:N/A:N.
EPSS exploit prediction
EPSS: 0.001 (0.9th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 1st percentile — 0.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
The 30-day trend appears once there are two daily scores.
Affected products
Weakness classification (CWE)
References
- github.com/rustls/rustls/security/advisories/GHSA-c8m5-c952-6cm4 (vendor-advisory)
- www.vulncheck.com/advisories/rustls-before-0.23.46-and-0.24.0-dev.1-before-0.24… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-123609?
- CVE-2026-123609 is a medium-severity vulnerability in Rustls, classified under Improper Removal of Sensitive Information Before Storage or Transfer. CVSS score: 4.0/10. Published 2026-11-08.
- How severe is CVE-2026-123609?
- Medium severity. CVSS v3 base score is 4.0 out of 10.