# CVE-2026-18663: Use after free in Red Hat Directory Server 11

> An unauthenticated remote attacker can cause a double-free and denial of service in 389-ds-base by sending a specific BIND request.

- **Severity:** Medium 5.9 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 12 Aug 2026
- **Updated:** 13 Aug 2026
- **Also known as:** DEBIAN-CVE-2026-18663, GHSA-m545-9vp4-qjrp, UBUNTU-CVE-2026-18663

## What is CVE-2026-18663?

CVE-2026-18663 is a medium-severity use after free vulnerability in Red Hat Directory Server 11, published on 12 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A flaw was found in 389-ds-base. The get_ldapmessage_controls_ext() function frees the parsed controls array on the Session Tracking critical-control rejection path without clearing the SLAPI_REQCONTROLS pblock slot. Operation teardown then frees the same pointer again, causing a double-free. An unauthenticated remote attacker can trigger this with a single BIND request carrying a critical Session Tracking control, resulting in heap corruption and potential denial of service.

Weakness: CWE-415 (Double Free)

## Which versions are affected by CVE-2026-18663?


## How do I fix CVE-2026-18663?

Apply the vendor's patch.

## Is CVE-2026-18663 being exploited?

There is no known exploitation of CVE-2026-18663 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-18663 and fix it if it is affected.

What it is: CVE-2026-18663 is a medium-severity use after free vulnerability in Red Hat Directory Server 11, published on 12 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-18663 in the wild and no public exploit code.

Affected product: Red Hat Directory Server 11. 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-2026-18663/ (Markdown: https://insights.sbomify.com/CVE-2026-18663/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-18663
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-18663
- OSV: https://osv.dev/vulnerability/CVE-2026-18663

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-18663/
Summaries are generated and may contain mistakes; the official description above is the record.