CVE-2026-123609 (CVSS 4)

Description

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.

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CVSS v3.1 Score

4.0

MEDIUM

CVSS:3.1/AV:L/AC:H/PR:H/UI:R/S:U/C:H/I:N/A:N

EPSS — Exploit Prediction

0.0010

Probability of exploitation

0.01%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-212 CWE-212

References

Other References

https://github.com/rustls/rustls/security/advisories/GHSA-c8m5-c952-6cm4 https://www.vulncheck.com/advisories/rustls-before-0.23.46-and-0.24.0-dev.1-before-0.24.0-dev.2-secret-exposure-via-debug

Frequently Asked Questions

What is 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. It has a CVSS v3.1 base score of 4.0 (MEDIUM).

How severe is CVE-2026-123609? +

CVE-2026-123609 has a CVSS v3.1 score of 4.0 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0010, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-123609? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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