Integer overflow in Mit Kerberos 5
CVE-2026-40356
In MIT Kerberos 5 (aka krb5) before 1.22.3, there is an integer underflow and resultant out-of-bounds read if an application calls gss_accept_sec_context() on a system with a NegoEx mechanism registered in /etc/gss/mech. An unauthenticated remote attacker can trigger this, possibly causing the process to terminate in parse_message.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.9 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.008 (54.3th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 54th percentile — 54.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.006 · newest: 0.008 · change: +0.002
Affected products
- Mit Kerberos 5 — versions 1.18
- Mit Kerberos 5
Weakness classification (CWE)
References
- web.mit.edu/kerberos/advisories/ (Vendor Advisory)
- cems.fun/2026/04/27/krb5-two-unauthenticated-network-vulnerabilities.html (Exploit, Patch, Third Party Advisory)
- github.com/krb5/krb5/commit/2e75f0d9362fb979f5fc92829431a590a130929f (Patch)
Frequently asked questions
- What is CVE-2026-40356?
- CVE-2026-40356 is a medium-severity vulnerability in Mit Kerberos 5, classified under Integer Underflow. CVSS score: 5.9/10. Published 2026-04-28.
- How severe is CVE-2026-40356?
- Medium severity. CVSS v3 base score is 5.9 out of 10.