CVE-2026-40355
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.
Predictions
Heuristic predictions, AS-IS, for prioritization only.
Mitigations
Mitigation details
CVE-2026-40355 NameCVE-2026-40355 DescriptionIn 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. SourceCVE (at NVD; CERT, ENISA, LWN, oss-sec,…
CVE-2026-40355
| Name | CVE-2026-40355 |
| 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. |
| Source | CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more) |
| References | DLA-4603-1, DSA-6293-1 |
| Debian Bugs | 1135317 |
Vulnerable and fixed packages
The table below lists information on source packages.
| Source Package | Release | Version | Status |
|---|---|---|---|
| krb5 (PTS) | bullseye | 1.18.3-6+deb11u5 | vulnerable |
| bullseye (security) | 1.18.3-6+deb11u8 | fixed | |
| bookworm | 1.20.1-2+deb12u4 | vulnerable | |
| bookworm (security) | 1.20.1-2+deb12u5 | fixed | |
| trixie | 1.21.3-5 | vulnerable | |
| trixie (security) | 1.21.3-5+deb13u1 | fixed | |
| forky, sid | 1.22.1-2.1 | fixed |
The information below is based on the following data on fixed versions.
| Package | Type | Release | Fixed Version | Urgency | Origin | Debian Bugs |
|---|---|---|---|---|---|---|
| krb5 | source | bullseye | 1.18.3-6+deb11u8 | DLA-4603-1 | ||
| krb5 | source | bookworm | 1.20.1-2+deb12u5 | DSA-6293-1 | ||
| krb5 | source | trixie | 1.21.3-5+deb13u1 | DSA-6293-1 | ||
| krb5 | source | (unstable) | 1.22.1-2.1 | 1135317 |
Notes
https://github.com/krb5/krb5/commit/2e75f0d9362fb979f5fc92829431a590a130929f
Apply commands
https://github.com/krb5/krb5/commit/2e75f0d9362fb979f5fc92829431a590a130929fOS impact
| OS | Version | Status | Fixed in |
|---|---|---|---|
| rhel | 9 | fixed | |
| debian | bookworm | fixed | 1.20.1-2+deb12u5 |
| debian | forky | fixed | 1.22.1-2.1 |
| debian | sid | fixed | 1.22.1-2.1 |
| debian | trixie | fixed | 1.21.3-5+deb13u1 |
| sles | affected | | |
| debian | bullseye | fixed | 1.18.3-6+deb11u8 |
References
- https://access.redhat.com/errata/RHSA-2026:19357
- https://cems.fun/2026/04/27/krb5-two-unauthenticated-network-vulnerabilities.html
- https://github.com/krb5/krb5/commit/2e75f0d9362fb979f5fc92829431a590a130929f
- https://web.mit.edu/kerberos/advisories/
- https://security-tracker.debian.org/tracker/CVE-2026-40355
- https://www.suse.com/security/cve/CVE-2026-40355.html
- https://access.redhat.com/errata/RHSA-2026:16799
- https://bugzilla.redhat.com/2463368
- https://bugzilla.redhat.com/2463370
- https://errata.almalinux.org/8/ALSA-2026-16799.html
- https://errata.almalinux.org/9/ALSA-2026-19357.html
CWEs
CWE-476
Community-verified mitigations for this CVE will appear above when contributors publish them.
Verify integrity in audit chain (admin only). AS-IS.