CVE-2026-40355: mit kerberos_5 NULL Pointer Dereference
Vulnerability summary
CVE-2026-40355 is a high (CVSS 7.5) NULL Pointer Dereference vulnerability in mit kerberos_5. EPSS estimates a 0.85% chance of exploitation in the next 30 days, higher than 57.3% of scored vulnerabilities. 1 public exploit is recorded.
Advisory lineage
Upstream 0 · Downstream 12 · Related 7Timeline
- 28-04-2026PublishedVulnerability first disclosed.
- 15-10-2026Last modifiedVulnerability information updated.
Description
In MIT Kerberos 5 (aka krb5) before 1.22.3, there is a NULL pointer dereference 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, causing the process to terminate in parse_nego_message.
CVSS metrics
4 scores · 4 sources · 1 version- CVE.orgCNA5.9MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:HDiffers
- OSV · UbuntuEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · DebianEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS trend
Probability
0.85%
Chance of exploitation in the next 30 days
Percentile
57%
Versus all other CVEs
30-day change
+0.24 pp
From 0.61% on 19-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
1 foundExploit Reference (cems.fun)
Maturity: unknown
Weaknesses
CWE · root causeAffected systems
Debian1 product
- krb5< 1.20.1-2+deb12u5 | < 1.21.3-5+deb13u1 | < 1.22.1-2.1
Mit1 product
- kerberos_5≥ 1.18, < 1.22.3 | ≥ 1.18.0, ≤ 1.22.2
Ubuntu1 product
- krb5< 1.19.2-2ubuntu0.8 | < 1.20.1-6ubuntu2.7 | All versions (No fix recorded) | < 1.22.1-2ubuntu4.1
3 vendors · 3 products
References
11 links- web.mit.edu/kerberos/advisories/Vendor Advisory
- cems.fun/2026/04/27/krb5-two-unauthenticated-network-vulnerabilities.htmlExploitPatchThird Party Advisory
