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

> A malicious cross-realm KDC can crash the MIT Kerberos KDC by sending a malformed S4U2Proxy request, causing denial of service.

- **Severity:** Medium 6.9 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 8 Oct 2026
- **Updated:** 14 Oct 2026
- **Also known as:** AZL-106836, BELL-CVE-2026-107708, DEBIAN-CVE-2026-107708, ECHO-1587-b13a-e744, GHSA-wc3c-9xc9-26g8, UBUNTU-CVE-2026-107708

## What is CVE-2026-107708?

CVE-2026-107708 is a medium-severity vulnerability in MIT krb5, published on 8 Oct 2026. An attacker needs administrator access to exploit it, with no action from the victim.

### 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.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2026-107708?


## How do I fix CVE-2026-107708?

Apply the vendor's patch.

## Is CVE-2026-107708 being exploited?

There is no known exploitation of CVE-2026-107708 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-107708 and fix it if it is affected.

What it is: CVE-2026-107708 is a medium-severity vulnerability in MIT krb5, published on 8 Oct 2026. An attacker needs administrator access to exploit it, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-107708 in the wild and no public exploit code.

Affected product: MIT krb5. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-107708/ (Markdown: https://insights.sbomify.com/CVE-2026-107708/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-107708
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-107708
- OSV: https://osv.dev/vulnerability/CVE-2026-107708

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-107708/
Summaries are generated and may contain mistakes; the official description above is the record.