CVE-2026-4748

# PoC Configuration for CVE-2026-4748 # Demonstration of rule dropping issue # Intended to block traffic from 192.168.1.0/24 range block in on em0 from 192.168.1.1 to 192.168.1.100 # Intended to block traffic from 10.0.0.0/24 range # Due to hash collision, this rule might be silently dropped block in on em0 from 10.0.0.1 to 10.0.0.100 # Mitigation: Use CIDR notation # block in on em0 from 192.168.1.0/24 # block in on em0 from 10.0.0.0/24

{"cve": {"id": "CVE-2026-4748", "sourceIdentifier": "[email protected]", "published": "2026-04-01T07:16:02.447", "lastModified": "2026-04-02T20:47:20.810", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "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.\n\nSome 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.\n\nAffected rules are silently ignored, which can lead to unexpected behaviour including over- and underblocking."}], "metrics": {"cvssMetricV31": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N", "baseScore": 7.5, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "availabilityImpact": "NONE"}, "exploitabilityScore": 3.9, "impactScore": 3.6}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-480"}, {"lang": "en", "value": "CWE-754"}, {"lang": "en", "value": "CWE-1023"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:*:*:*:*:*:*:*:*", "versionStartIncluding": "14.0", "versionEndExcluding": "14.4", "matchCriteriaId": "B18512F3-168B-42C3-9579-58A44E18B50B"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:14.3:-:*:*:*:*:*:*", "matchCriteriaId": "9DC7C54E-58AF-4ADE-84AF-0EF0F325E20E"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:14.3:p1:*:*:*:*:*:*", "matchCriteriaId": "D3D22B8C-36CF-4800-9673-0B0240558BDD"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:14.3:p2:*:*:*:*:*:*", "matchCriteriaId": "242FA2A8-5D7D-4617-A411-2651FF3A3E4C"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:14.3:p3:*:*:*:*:*:*", "matchCriteriaId": "40573F60-F3B7-4AEC-846A-B08E5B7D9D00"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:14.3:p4:*:*:*:*:*:*", "matchCriteriaId": "1FB832CE-0A98-44A2-8BAC-CD38A64279B6"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:14.3:p5:*:*:*:*:*:*", "matchCriteriaId": "9A785F8E-C218-41AE-8D57-BF06DDAEF7CB"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:14.3:p6:*:*:*:*:*:*", "matchCriteriaId": "C3909FDD-B2A2-45B6-A40B-1D303A717F15"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:14.3:p7:*:*:*:*:*:*", "matchCriteriaId": "720597A2-F181-46E1-8A0D-097E17ADC4FB"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:14.3:p8:*:*:*:*:*:*", "matchCriteriaId": "DC8A75D0-148A-427A-9783-45477EABED21"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:14.3:p9:*:*:*:*:*:*", "matchCriteriaId": "F5D39FC9-6DBA-46C8-BB80-A6188E6A8527"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:14.4:-:*:*:*:*:*:*", "matchCriteriaId": "8F3856BE-666F-4FA1-A6AD-FE179CEBF1E4"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:14.4:rc1:*:*:*:*:*:*", "matchCriteriaId": "0342A715-E211-4AF6-97ED-32EB9EBB947D"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:15.0:-:*:*:*:*:*:*", "matchCriteriaId": "368CFE5D-C5C2-42AF-AAF4-28DFE1A59C3B"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:15.0:p1:*:*:*:*:*:*", "matchCriteriaId": "AA4AAA57-70A7-4717-ACF2-A253E757FF2C"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:15.0:p2:*:*:*:*:*:*", "matchCriteriaId": "E24ABFA6-4D12-4DE5-832B-438502C7D188"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:15.0:p3:*:*:*:*:*:*", "matchCriteriaId": "C1C9869C-494B-4628-9AA3-4AA5B989C377"}, {"vulnerable": true, "criteria": "cpe:2.3:o:freebsd:freebsd:15.0:p4:*:*:*:*:*:*", "matchCriteriaId": "002AA2FE-C7BA-471A-9434-0E56A878ACBF"}]}]}], "references": [{"url": "https://security.freebsd.org/advisories/FreeBSD-SA-26:09.pf.asc", "source": "[email protected]", "tags": ["Vendor Advisory"]}]}}