Summaryinfo

A vulnerability was found in FreeBSD up to p0.x/p4/p9. It has been declared as critical. Impacted is an unknown function of the component Hash Calculation Handler. The manipulation results in incorrect operator. This vulnerability is reported as CVE-2026-4748. The attack can be launched remotely. No exploit exists. It is advisable to implement a patch to correct this issue.

Detailsinfo

A vulnerability, which was classified as critical, was found in FreeBSD up to p0.x/p4/p9. Affected is some unknown processing of the component Hash Calculation Handler. The manipulation with an unknown input leads to a incorrect operator vulnerability. CWE is classifying the issue as CWE-480. The product accidentally uses the wrong operator, which changes the logic in security-relevant ways. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

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.

The weakness was disclosed by Michael Gmelin. The advisory is shared for download at security.freebsd.org. This vulnerability is traded as CVE-2026-4748 since 03/24/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. There are neither technical details nor an exploit publicly available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 04/01/2026).

Applying a patch is able to eliminate this problem.

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Productinfo

Type

• Operating System

Name

• FreeBSD

Version

• p0.x
• p4
• p9

License

• open-source

Website

• Product: https://www.freebsd.org/

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