FreeBSD : FreeBSD -- TCP spoofing vulnerability in pf(4) (9cbbc506-93c1-11ee-8e38-002590c1f29c)

high Nessus Plugin ID 186607



The remote FreeBSD host is missing one or more security-related updates.


The version of FreeBSD installed on the remote host is prior to tested version. It is, therefore, affected by a vulnerability as referenced in the 9cbbc506-93c1-11ee-8e38-002590c1f29c advisory.

- As part of its stateful TCP connection tracking implementation, pf performs sequence number validation on inbound packets. This makes it difficult for a would-be attacker to spoof the sender and inject packets into a TCP stream, since crafted packets must contain sequence numbers which match the current connection state to avoid being rejected by the firewall. A bug in the implementation of sequence number validation means that the sequence number is not in fact validated, allowing an attacker who is able to impersonate the remote host and guess the connection's port numbers to inject packets into the TCP stream. An attacker can, with relatively little effort, inject packets into a TCP stream destined to a host behind a pf firewall. This could be used to implement a denial-of-service attack for hosts behind the firewall, for example by sending TCP RST packets to the host. (CVE-2023-6534)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.


Update the affected packages.

See Also

Plugin Details

Severity: High

ID: 186607

File Name: freebsd_pkg_9cbbc50693c111ee8e38002590c1f29c.nasl

Version: 1.4

Type: local

Published: 12/5/2023

Updated: 12/20/2023

Configuration: Enable paranoid mode

Supported Sensors: Nessus

Risk Information


Risk Factor: Medium

Score: 4.4


Risk Factor: High

Base Score: 7.8

Temporal Score: 5.8

Vector: CVSS2#AV:N/AC:L/Au:N/C:N/I:N/A:C

CVSS Score Source: CVE-2023-6534


Risk Factor: High

Base Score: 7.5

Temporal Score: 6.5

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

CPE: p-cpe:/a:freebsd:freebsd:freebsd-kernel, cpe:/o:freebsd:freebsd

Required KB Items: Host/local_checks_enabled, Settings/ParanoidReport, Host/FreeBSD/release, Host/FreeBSD/pkg_info

Exploit Ease: No known exploits are available

Patch Publication Date: 12/5/2023

Vulnerability Publication Date: 12/5/2023

Reference Information

CVE: CVE-2023-6534

IAVA: 2023-A-0676