CVE-2001-0183

FreeBSD <= 4.2 - Unauthenticated Access Restriction Bypass via TCP ECE Flag

Title source: llm
STIX 2.1

Exploitation Summary

EIP tracks 1 public exploit for CVE-2001-0183. PoCs published by Aragon Gouveia.

AI-analyzed exploit summary The vulnerability in FreeBSD's packet filtering allows unauthorized packets with the ECE flag set to bypass established connection rules, potentially granting remote access to protected services. The provided text is a description rather than functional exploit code.

Description

ipfw and ip6fw in FreeBSD 4.2 and earlier allows remote attackers to bypass access restrictions by setting the ECE flag in a TCP packet, which makes the packet appear to be part of an established connection.

Exploits (1)

exploitdb WRITEUP VERIFIED
by Aragon Gouveia · textremotefreebsd
https://www.exploit-db.com/exploits/20593

The vulnerability in FreeBSD's packet filtering allows unauthorized packets with the ECE flag set to bypass established connection rules, potentially granting remote access to protected services. The provided text is a description rather than functional exploit code.

Classification
Writeup 90%
Attack Type
Auth Bypass
Complexity
Moderate
Reliability
Theoretical
Target: FreeBSD (IPv4/IPv6 packet filtering)
No auth needed
Prerequisites: Network access to target system · Ability to craft TCP packets with ECE flag
mistral-large-3 · analyzed Feb 16, 2026 Full analysis →

References (6)

Core 6
Core References
Exploit, Patch, Vendor Advisory vdb-entry x_refsource_bid
http://www.securityfocus.com/bid/2293
Third Party Advisory, US Government Resource third-party-advisory government-resource x_refsource_ciac
http://www.ciac.org/ciac/bulletins/l-029.shtml
Various Sources mailing-list x_refsource_bugtraq
http://www.security-express.com/archives/bugtraq/2001-01/0424.html
Third Party Advisory, VDB Entry vdb-entry x_refsource_xf
https://exchange.xforce.ibmcloud.com/vulnerabilities/5998
Patch, Vendor Advisory vendor-advisory x_refsource_freebsd
ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-01:08.ipfw.asc
Third Party Advisory, VDB Entry vdb-entry x_refsource_osvdb
http://www.osvdb.org/1743

Scores

EPSS 0.0809
EPSS Percentile 94.2%

Details

Status published
Products (10)
freebsd/freebsd 3.0
freebsd/freebsd 3.1
freebsd/freebsd 3.3
freebsd/freebsd 3.4
freebsd/freebsd 3.5
freebsd/freebsd 3.5.1
freebsd/freebsd 4.0 (2 CPE variants)
freebsd/freebsd 4.1
freebsd/freebsd 4.1.1
freebsd/freebsd 4.2
Published Mar 26, 2001
Tracked Since Feb 18, 2026