# CVE-2026-18453: Null dereference in Red Hat Directory Server 11.5 E4S for RHEL 8

> An unauthenticated remote attacker can crash the LDAP server by sending crafted search requests with the USE_ONE_BACKEND control, causing a denial of service.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/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:** 7 Sep 2026
- **Updated:** 8 Oct 2026
- **Also known as:** AZL-99974, DEBIAN-CVE-2026-18453, GHSA-42wr-8m7m-5j62, UBUNTU-CVE-2026-18453

## What is CVE-2026-18453?

CVE-2026-18453 is a high-severity vulnerability in Red Hat Directory Server 11.5 E4S for RHEL 8, published on 7 Sep 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 Directory Server. A missing NULL pointer check in the paged results handling of op_shared_search allows an unauthenticated remote attacker to crash the LDAP server by sending a crafted sequence of search requests using the USE_ONE_BACKEND control, resulting in denial of service.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2026-18453?


## How do I fix CVE-2026-18453?

Apply the vendor's patch.

## Is CVE-2026-18453 being exploited?

There is no known exploitation of CVE-2026-18453 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-18453 and fix it if it is affected.

What it is: CVE-2026-18453 is a high-severity vulnerability in Red Hat Directory Server 11.5 E4S for RHEL 8, published on 7 Sep 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-2026-18453 in the wild and no public exploit code.

Affected product: Red Hat Directory Server 11.5 E4S for RHEL 8. 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-2026-18453/ (Markdown: https://insights.sbomify.com/CVE-2026-18453/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-18453
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-18453
- OSV: https://osv.dev/vulnerability/CVE-2026-18453

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-18453/
Summaries are generated and may contain mistakes; the official description above is the record.