Vulnerability · Published Oct 8, 2026 · Assigned by VulnCheck
CVE-2026-107708MIT krb5 through 1.22.2 KDC NULL Pointer Dereference via S4U2Proxy PAC
Medium 4.9
In plain English
A medium-severity null pointer dereference in krb5 from MIT. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 44% of all known vulnerabilities).
Severity (CVSS 3.1)4.9Medium
Exploit odds (30 days)0.5%top 55.6% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official description
MIT krb5 through 1.22.2 contains a NULL pointer dereference vulnerability in the KDC's get_pac_princ_with_realm() that returns success while leaving the client principal NULL on malformed names. A malicious or compromised cross-realm trusted KDC can send an S4U2Proxy request with a PAC carrying a malformed client name to crash krb5kdc and deny authentication.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | krb5 | no fix listed | DEBIAN-CVE-2026-107708 |
| Debian:13 | krb5 | no fix listed | DEBIAN-CVE-2026-107708 |
| Debian:14 | krb5 | no fix listed | DEBIAN-CVE-2026-107708 |
| Ubuntu:22.04:LTS | krb5 | no fix listed | UBUNTU-CVE-2026-107708 |
| Ubuntu:24.04:LTS | krb5 | no fix listed | UBUNTU-CVE-2026-107708 |
| Ubuntu:26.04:LTS | krb5 | no fix listed | UBUNTU-CVE-2026-107708 |
| Ubuntu:26.10 | krb5 | no fix listed | UBUNTU-CVE-2026-107708 |
Affected products (as reported)
Weakness: CWE-476 · Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
References
- Pull Request #1510 issue-tracking, patch
- Patch Commit patch
- https://github.com/krb5/krb5/commit/a88a18cafa1040a0c4f9c8d08288fc98831ec86d patch
- https://github.com/krb5/krb5/blob/krb5-1.22.2-final/src/kdc/kdc_util.c#L639-L676 technical-description
- https://github.com/krb5/krb5 product
- VulnCheck Advisory: MIT krb5 through 1.22.2 KDC NULL Pointer Dereference via S4U2Proxy PAC third-party-advisory