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FreeBSD : FreeBSD -- Jail chroot escape via fd exchange with a different jail (a88f5b2d-11e9-11f1-8148-bc241121aa0a)

high Nessus Plugin ID 300106

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Synopsis

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

Description

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 a88f5b2d-11e9-11f1-8148-bc241121aa0a advisory.

 If two sibling jails are restricted to separate filesystem trees, which is to say that neither of the two jail root directories is an ancestor of the other, jailed processes may nonetheless be able to access a shared directory via a nullfs mount, if the administrator has configured one.
 In this case, cooperating processes in the two jails may establish a connection using a unix domain socket and exchange directory descriptors with each other.
 When performing a filesystem name lookup, at each step of the lookup, the kernel checks whether the lookup would descend below the jail root of the current process. If the jail root directory is not encountered, the lookup continues.
 In a configuration where processes in two different jails are able to exchange file descriptors using a unix domain socket, it is possible for a jailed process to receive a directory for a descriptor that is below that process' jail root. This enables full filesystem access for a jailed process, breaking the chroot.
 Note that the system administrator is still responsible for ensuring that an unprivileged user on the jail host is not able to pass directory descriptors to a jailed process, even in a patched kernel.

Tenable has extracted the preceding description block directly from the FreeBSD security advisory.

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

Solution

Update the affected packages.

See Also

http://www.nessus.org/u?5409b34f

Plugin Details

Severity: High

ID: 300106

File Name: freebsd_pkg_a88f5b2d11e911f18148bc241121aa0a.nasl

Version: 1.4

Type: local

Published: 2/28/2026

Updated: 3/19/2026

Configuration: Enable paranoid mode

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: High

Score: 7.9

CVSS v2

Risk Factor: Medium

Base Score: 5.5

Temporal Score: 4.1

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

CVSS Score Source: CVE-2025-15576

CVSS v3

Risk Factor: High

Base Score: 7.5

Temporal Score: 6.5

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

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

Vulnerability Information

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

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: 2/25/2026

Vulnerability Publication Date: 2/25/2026

Reference Information

CVE: CVE-2025-15576

IAVA: 2026-A-0203