# CVE-2026-4748: pf silently ignores certain rules

> A regression in FreeBSD's pf firewall causes certain address range rules to be silently ignored, potentially leading to unexpected over- or underblocking of network traffic.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 1 Apr 2026
- **Updated:** 1 Apr 2026
- **Also known as:** GHSA-2v62-qxwf-qh42

## What is CVE-2026-4748?

CVE-2026-4748 is a high-severity vulnerability in Freebsd Freebsd, published on 1 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A regression in the way hashes were calculated caused rules containing the address range syntax (x.x.x.x - y.y.y.y) that only differ in the address range(s) involved to be silently dropped as duplicates.  Only the first of such rules is actually loaded into pf.  Ranges expressed using the address[/mask-bits] syntax were not affected.

Some keywords representing actions taken on a packet-matching rule, such as 'log', 'return tll', or 'dnpipe', may suffer from the same issue.  It is unlikely that users have such configurations, as these rules would always be redundant.

Affected rules are silently ignored, which can lead to unexpected behaviour including over- and underblocking.

Weakness: CWE-754 (Improper Check for Unusual or Exceptional Conditions), CWE-480 (Use of Incorrect Operator), CWE-1023 (Incomplete Comparison with Missing Factors)

## Which versions are affected by CVE-2026-4748?

It affects 1 product.


Products: Freebsd Freebsd.

## How do I fix CVE-2026-4748?

No fix has been published for CVE-2026-4748 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-4748 being exploited?

There is no known exploitation of CVE-2026-4748 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-2026-4748 and fix it if it is affected.

What it is: CVE-2026-4748 is a high-severity vulnerability in Freebsd Freebsd, published on 1 Apr 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-2026-4748 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-2026-4748/ (Markdown: https://insights.sbomify.com/CVE-2026-4748/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-4748
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-4748
- OSV: https://osv.dev/vulnerability/CVE-2026-4748

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-4748/
Summaries are generated and may contain mistakes; the official description above is the record.