# CVE-2026-104039: Sssd: sssd: denial of service via stale connection state reuse in pam gssapi responder

> A local attacker can cause a denial of service in SSSD by triggering a use-after-free in the PAM GSSAPI responder, crashing the authentication service.

- **Severity:** Medium 4.7 (`CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 6 Oct 2026
- **Updated:** 16 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-104039, GHSA-6ffw-v8mm-gqgh, UBUNTU-CVE-2026-104039

## What is CVE-2026-104039?

CVE-2026-104039 is a medium-severity use after free vulnerability in Red Hat Enterprise Linux 10, published on 6 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A flaw was found in SSSD. A local user can cause a denial of service (DoS) by disrupting system authentication services. When handling Generic Security Services Application Programming Interface (GSSAPI) authentication in the Pluggable Authentication Module (PAM) responder, cached connection state is freed upon completion without clearing the reference pointer. An attacker can exploit this by sending an additional request over the same connection, causing the service to access invalid memory and unexpectedly terminate.

Weakness: CWE-825 (Expired Pointer Dereference)

## Which versions are affected by CVE-2026-104039?


## How do I fix CVE-2026-104039?

No fix has been published for CVE-2026-104039 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-104039 being exploited?

There is no known exploitation of CVE-2026-104039 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-104039 and fix it if it is affected.

What it is: CVE-2026-104039 is a medium-severity use after free vulnerability in Red Hat Enterprise Linux 10, published on 6 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-104039 in the wild and no public exploit code.

Affected product: Red Hat Enterprise Linux 10. 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-2026-104039/ (Markdown: https://insights.sbomify.com/CVE-2026-104039/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-104039
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-104039
- OSV: https://osv.dev/vulnerability/CVE-2026-104039

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-104039/
Summaries are generated and may contain mistakes; the official description above is the record.