# CVE-2026-2261: blocklistd(8) socket leak

> An attacker can exhaust file descriptors in FreeBSD's blocklistd by triggering adverse events, disabling IP blocking and causing system slowdowns.

- **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:** No
- **Published:** 9 Mar 2026
- **Updated:** 11 Mar 2026
- **Also known as:** GHSA-5cm6-5xpq-xrwv

## What is CVE-2026-2261?

CVE-2026-2261 is a high-severity denial of service vulnerability in Freebsd Freebsd, published on 9 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Due to a programming error, blocklistd leaks a socket descriptor for each adverse event report it receives.

Once a certain number of leaked sockets is reached, blocklistd becomes unable to run the helper script: a child process is forked, but this child dereferences a null pointer and crashes before it is able to exec the helper.  At this point, blocklistd still records adverse events but is unable to block new addresses or unblock addresses whose database entries have expired.

Once a second, much higher number of leaked sockets is reached, blocklistd becomes unable to receive new adverse event reports.

An attacker may take advantage of this by triggering a large number of adverse events from sacrificial IP addresses to effectively disable blocklistd before launching an attack.

Even in the absence of attacks or probes by would-be attackers, adverse events will occur regularly in the course of normal operations, and blocklistd will gradually run out file descriptors and become ineffective.

The accumulation of open sockets may have knock-on effects on other parts of the system, resulting in a general slowdown until blocklistd is restarted.

Weakness: CWE-772 (Missing Release of Resource after Effective Lifetime)

## Which versions are affected by CVE-2026-2261?

It affects 1 product.


Products: Freebsd Freebsd.

## How do I fix CVE-2026-2261?

No fix has been published for CVE-2026-2261 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-2261 being exploited?

There is no known exploitation of CVE-2026-2261 in the wild and no public exploit code.

## Other vulnerabilities in Freebsd Freebsd

- [CVE-2018-17160](https://insights.sbomify.com/CVE-2018-17160/): Memory corruption in FreeBSD (critical 10.0)
- [CVE-2014-3954](https://insights.sbomify.com/CVE-2014-3954/): Memory corruption in n/a (critical 10.0)
- [CVE-2006-4304](https://insights.sbomify.com/CVE-2006-4304/): Memory corruption in n/a (critical 10.0)
- [CVE-2006-0226](https://insights.sbomify.com/CVE-2006-0226/): Integer overflow in n/a (critical 10.0)
- [CVE-2004-0002](https://insights.sbomify.com/CVE-2004-0002/): Denial of service in n/a (critical 10.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-2261 and fix it if it is affected.

What it is: CVE-2026-2261 is a high-severity denial of service vulnerability in Freebsd Freebsd, published on 9 Mar 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-2026-2261 in the wild and no public exploit code.

Affected product: Freebsd Freebsd. 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-2026-2261/ (Markdown: https://insights.sbomify.com/CVE-2026-2261/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-2261
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-2261
- OSV: https://osv.dev/vulnerability/CVE-2026-2261

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-2261/
Summaries are generated and may contain mistakes; the official description above is the record.