FreeBSD 15 — python313t — multiple vulnerabilities (5 CVEs) — patch and remediation guide

📖 ~4 min read  •  Source: FreeBSD VuXML

VuXML topic: Python — The webbrowser.open() API allows leading dashes

Related CVEs: CVE-2025-15366 CVE-2025-15367 CVE-2026-0865 CVE-2026-1299 CVE-2026-4519

Upstream summary: https://github.com/python/cpython/pull/143931 reports: The webbrowser.open() API would accept leading dashes in the URL which could be handled as command line options for certain web browsers. New behavior rejects leading dashes. Users are recommended to sanitize URLs prior to passing to webbrowser.open().

Table of contents

1. Symptom & Impact
2. Environment & Reproduction
3. Root Cause Analysis
4. Quick Triage
5. Step-by-Step Diagnosis
6. Solution – Primary Fix
7. Solution – Alternative Approaches
8. Verification & Acceptance Criteria
9. Rollback Plan
10. Prevention & Hardening
11. Related Errors & Cross-Refs
12. References & Further Reading

Symptom & Impact

python313t is executed by every process started from it, so a flaw here surfaces inside your applications rather than in python313t itself: header-parsing and request-smuggling bugs in the bundled HTTP stack, weaknesses in the runtime’s own TLS and crypto code, unsafe archive, XML or deserialisation handling in the standard library, or memory-safety bugs in the JIT. Long-lived workers such as application servers, JVM daemons and resident node processes keep executing the old build after FreeBSD 15 replaces it on disk, so a patched machine stays exposed until each one is restarted. python313t is an interpreter or virtual machine plus its standard library, not a daemon: it runs only inside processes you start, so there is no python313t service to restart — restart the applications that execute it instead.

Environment & Reproduction

Reproduction targets FreeBSD 15. Confirm release, installed package, and capture baseline state:

freebsd-version -kru
uname -a
pkg info python313t
pkg query "%n-%v" python313t
pkg audit -F
service -e

Exercise the workload that uses python313t while collecting:

tail -200 /var/log/messages
dmesg -a | tail -200
tail -200 /var/log/pkg.log

Root Cause Analysis

Root cause is tracked at FreeBSD VuXML. The FreeBSD ports security team shipped a corrective python313t port revision; hosts on an outdated build remain exposed. Correlate package logs with system logs and kernel state to isolate the change that triggered the failure mode:

tail -500 /var/log/pkg.log
tail -500 /var/log/messages
sysctl kern.lastpid
sysctl kern.osreldate     # numeric __FreeBSD_version, e.g. 1400097

Quick Triage

Run these checks on FreeBSD 15 to confirm the failure mode and current state of python313t:

pkg version -v python313t                # installed vs available version
pkg audit python313t                     # advisory match for this package
tail -100 /var/log/messages
dmesg -a | tail -100
kldstat                              # kernel module state (for kernel/driver pkgs)
pfctl -sr 2>/dev/null || ipfw list   # only if pf/ipfw is enabled
# e.g. bind918→named, php83→php-fpm), check it:
pkg query '%Fp' python313t | sed -n 's|.*/etc/rc\.d/||p'  # FreeBSD: the REAL service name(s) = basename of the rc.d script (bind918 -> named, postgresql16-server -> postgresql, apache24 -> apache24)
pkg query '%b' python313t  # FreeBSD: shared libraries PROVIDED by python313t. Non-empty here + no rc.d script = it is a library: patch it, then restart its consumers

Step-by-Step Diagnosis

1. List enabled services (only relevant if the package provides one).

   service -e

2. Follow live logs.

   tail -F /var/log/messages
   dmesg

3. Validate firewall rules (skip if neither pf nor ipfw is enabled).

   pfctl -sr -v 2>/dev/null || ipfw show

4. Check package integrity for python313t.

   pkg check -B python313t
   pkg check -d python313t    # verify shared-library deps

5. Reinstall python313t if integrity check fails.

   pkg install -fy python313t

6. Correlate findings with /var/log/pkg.log and FreeBSD VuXML to pin the commit that introduced the regression.

Solution – Primary Fix

Install the corrective python313t port revision referenced by FreeBSD VuXML:

sudo pkg update
sudo pkg upgrade python313t              # or: sudo pkg upgrade -y for the whole system
pkg audit python313t                    # confirm no remaining advisory for this package

For ports-tree builders (FreeBSD 13.x and earlier used portsnap; on FreeBSD 14+ the ports tree is fetched with Git):

# FreeBSD 14+ (portsnap was removed):
sudo pkg install -y git-lite
sudo git clone --depth 1 https://git.FreeBSD.org/ports.git /usr/ports
# FreeBSD 13.x and earlier:
# sudo portsnap fetch update
cd /usr/ports/<category>/python313t
sudo make deinstall reinstall clean

Reboot only if the package ships a kernel module or replaces a shared library used by long-running daemons.

Solution – Alternative Approaches

If the primary fix is not viable, choose from these alternatives:

• Lock the package until the fix is vetted:

  sudo pkg lock python313t

• Downgrade to a known-good revision. pkg install pkgname-VERSION is not a real downgrade syntax — fetch a specific build instead:

  # 1. Discover available versions across configured repos:
  pkg search -e python313t
  pkg rquery -r FreeBSD-quarterly '%n-%v' python313t
  # 2. Install from a specific saved .pkg file:
  sudo pkg add -f /path/to/python313t-<older-version>.pkg
  # 3. Or switch the host repo to the quarterly branch (see snippet below) and:
  sudo pkg upgrade -fr FreeBSD-quarterly python313t

• Switch the pkg repository between quarterly and latest by editing /usr/local/etc/pkg/repos/FreeBSD.conf:

  FreeBSD: {
    url: "pkg+https://pkg.FreeBSD.org/${ABI}/quarterly",
    mirror_type: "srv",
    signature_type: "fingerprints",
    fingerprints: "/usr/share/keys/pkg",
    enabled: yes
  }

• Isolate the affected service in a jail with stricter firewall rules:

  iocage create -n python313t-jail -r 15.0-CURRENT
  iocage set allow_raw_sockets=0 python313t-jail
  # or with Bastille:
  bastille create python313t-jail 15.0-CURRENT 10.0.0.10

• Replace the service with a vendored static build for the period between exposure detection and full rollout.

Verification & Acceptance Criteria

All of these should pass after the fix:

pkg info python313t                # shows the expected fixed version
pkg audit python313t               # no advisory for this package (exit code 0)
tail -50 /var/log/messages   # no new errors after upgrade
# If python313t ships a service, confirm it is running under its rc.d name:

The conditions described in the advisory must no longer be reported for python313t across two consecutive runs.

Rollback Plan

Capture state before any change (only ZFS root has boot environments — UFS hosts skip bectl):

pkg query "%n-%v" > /root/pkg-pre.txt
# ZFS-on-root only:
sudo bectl create pre-python313t-patch

To revert if the upgrade is bad, reinstall the previously saved .pkg file:

sudo pkg add -f /var/cache/pkg/python313t-<previous-version>.pkg
# Or activate the pre-patch boot environment and reboot (ZFS-on-root only):
sudo bectl activate pre-python313t-patch
sudo shutdown -r now

For kernel/loader changes on a UFS host, boot the previous kernel from the loader prompt (press 3 at the menu, then boot kernel.old).

Prevention & Hardening

Prevent recurrence on FreeBSD 15 hosts running python313t:

• Enable the daily security pkg audit in /etc/periodic.conf:

  daily_status_security_pkgaudit_enable="YES"

• Subscribe to freebsd-security-notifications at lists.freebsd.org.

• Mirror through a local pkg repository managed by poudriere:

  poudriere jail -c -j 15amd64 -v 15.0-CURRENT
  poudriere ports -c -p default
  poudriere bulk -j 15amd64 -p default <category>/python313t

• Version-pin sensitive packages:

  sudo pkg lock python313t

• Take an automatic ZFS boot-environment snapshot before every upgrade (ZFS root only):

  sudo bectl create pre-upgrade-$(date +%Y%m%d)

• Monitor file integrity (create a baseline, verify against it later):

  # Create a baseline (use -c; target /usr/local/etc, /etc, /boot — NOT /):
  sudo mtree -c -K sha256digest -p /usr/local/etc > /var/db/usr-local-etc.mtree
  sudo mtree -c -K sha256digest -p /etc          > /var/db/etc.mtree
  # Verify later:
  sudo mtree -p /usr/local/etc < /var/db/usr-local-etc.mtree
  # Or with AIDE for a richer ruleset:
  sudo pkg install -y aide && sudo aide --init && sudo aide --check

• Harden jails with allow.* tunables in /etc/jail.conf:

  python313t_jail {
    allow.raw_sockets = 0;
    allow.sysvipc    = 0;
    allow.mount      = 0;
    allow.chflags    = 0;
  }

Related Errors & Cross-Refs

Issues that commonly surface alongside a python313t update: pkg lock contention, mismatched ABI after kernel/userland skew, pf rule drift, and stale shared-library references after upgrade. Triage with:

freebsd-version -kru
uname -K
pkg check -d
pfctl -sr

View all freebsd-15 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Primary reference: FreeBSD VuXML. Useful manual pages on FreeBSD 15:

man pkg
man freebsd-update
man pfctl
man ipfw
man bectl
man periodic.conf

Other resources: the FreeBSD Handbook, the FreeBSD Security Advisories at security.freebsd.org, and the /usr/ports/UPDATING file for port-specific notes implicated in this advisory.