pf silently ignores certain rules

published 2026-04-01 7 mo ago modified 2026-06-17 4 mo ago also EUVD-2026-17818

cvss: 7.5; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.3%; EPSS 0.3% chance of exploitation in 30 days, percentile 17%
public exploits: 0; none known

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.

Patch / fix

fixed in 1

FreeBSD FreeBSD p1, p5, p10

CISA SSVC

Exploitation: none
Automatable: yes
Technical impact: partial
Assessed: 7 mo ago (2026-04-01)

Exploit prediction

0.25% chance of exploitation in the next 30 days, higher than 17% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CISA ADP	3.1	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
CNA	3.1	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Affected products

FreeBSD FreeBSD

Classification

Weakness

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

References

security.freebsd.org /advisories/FreeBSD-SA-26:09.pf.asc
vendor-advisory

Sources

CVE List CVE-2026-4748
NVD CVE-2026-4748

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary