CVE-2026-0265 Vulnerability Assessment Tool

Safely determine whether a Palo Alto Networks PAN-OS GlobalProtect portal is vulnerable to CVE-2026-0265 without authenticating any session or modifying any state.

Description

CVE-2026-0265 is a remote authentication bypass affecting PAN-OS and Panorama that triggers when an authentication profile uses Cloud Authentication Service (CAS). The vulnerable pan_auth_verify function in libpanmp_mp.so dispatches JSON Web Token signature verification purely on the attacker-controlled alg header — a forged JWT with alg=HS256 and HMAC-SHA256(cas_public_key_pem, header.payload) as its signature is accepted as if it were a real RS256-signed CAS token, letting any attacker impersonate any user.

The bug is reachable through two attack surfaces — the GlobalProtect portal (/saml/acs.esp, yields a VPN session) and the management UI (/SAML20/SP/ACS, yields full PAN-OS administrator). This tool covers the GlobalProtect portal surface only.

How it works

A single anonymous GET /global-protect/prelogin.esp request reveals everything needed for an authoritative verdict:

1. Precondition factor — The prelogin response carries an XML element <cas-auth>yes|no</cas-auth> set directly by the portal's auth configuration. A value of yes confirms the CVE precondition is met for this listener.
2. Build factor — When CAS is attached, the same response embeds an outbound CAS request token in its <saml-request> field. Decoding it yields the firewall's authoritative version string, which is then cross-referenced against the vendor advisory's per-base patched-hotfix matrix to produce the verdict.
3. .saas short-circuit — PA cloud-managed builds are not affected per Palo Alto's clarification (2026-05-21), regardless of the underlying base build number.

Output is intentionally minimal

The script emits the verdict, the firewall's reported PanOS version (so a defender can sanity-check the assessment against their inventory), and basic triage context (prelogin_status, prelogin_msg, http_status, error notes). If your pipeline needs richer appliance metadata, cross-reference the target URL against your own inventory.

Installation

git clone https://github.com/BishopFox/CVE-2026-0265-check
cd CVE-2026-0265-check
pip install requests

Requires Python 3.9+ and the requests package.

Usage

Pass one or more targets as positional arguments, via --targets-file, or on stdin. Hostnames and host:port strings are auto-wrapped to https://.

python3 CVE-2026-0265-check.py [options] <target> [<target>...]

Flag	Meaning
-f, --targets-file FILE	Read one target per line from FILE
-t, --timeout SECONDS	Per-request timeout. Default: 20.0
-c, --concurrent N	Max parallel targets. Default: 5
-b, --brief	Emit <url>\t<verdict>\t<panos_version> per target instead of full JSON
--user-agent UA	Override probe User-Agent. The default is a browser-like Chrome string that bypasses gpsvc's GP-client version gate; use a custom UA if you need access-log audit visibility and don't need the version-gated path.

Default output is one JSON object per target on stdout (jq-friendly).

Verdicts

The script emits one of three classes of verdict per target. Determined verdicts answer the vulnerability question authoritatively for that target. Undetermined verdicts indicate the probe could not reach a conclusion and operator follow-up is required.

Determined — vulnerable

Verdict	When
VULNERABLE	CAS attached, PanOSversion strictly below the advisory's patched hotfix for this base, not .saas.

Determined — not vulnerable

Verdict	When
PATCHED	CAS attached, PanOSversion at or above the advisory's patched hotfix for this base.
NOT-AFFECTED-SAAS	CAS attached but PanOSversion has the .saas suffix (PA cloud-managed; not affected per PA 2026-05-21).
NOT-AFFECTED-NO-CAS	Prelogin returned successfully but <cas-auth> indicates SAML / RADIUS / LDAP / local auth. CVE doesn't apply to this listener.
NOT-AFFECTED-NOT-GLOBALPROTECT	Response shape isn't a GP portal (e.g. "GlobalProtect portal does not exist"). Out of scope.

Undetermined — operator follow-up required

Verdict	When	Suggested follow-up
UNDETERMINED-VERSION-GATED	gpsvc returned "CAS is not supported by the client". CAS is attached but the probe was rejected for User-Agent reasons; PanOSversion cannot be read from this response.	Retry with --user-agent set to a real GP-client string.
UNDETERMINED-MTLS-GATED	"Valid client certificate is required" in the prelogin response. Auth surface hidden behind an mTLS gate.	Confirm the build via a separate channel (customer's authoritative version, or a probe with a valid client cert).
UNDETERMINED-ERROR	Network failure, malformed response, unparsable PanOSversion, or Token decode failure despite cas-auth=yes.	Re-run; if persistent, the target is probably not reachable from this position.

Example output

Brief mode, mixed targets

$ python3 CVE-2026-0265-check.py -b -f targets.txt
https://gp1.customer.example         VULNERABLE                       11.1.6-h23
https://gp2.customer.example         PATCHED                          11.1.6-h32
https://vpn.cloud.customer.example   NOT-AFFECTED-SAAS                11.2.7-h9.saas
https://mgmt.customer.example        NOT-AFFECTED-NO-CAS              -
https://www.customer.example         NOT-AFFECTED-NOT-GLOBALPROTECT   -
https://internal-vpn.customer.example UNDETERMINED-MTLS-GATED         -

JSON mode (default)

$ python3 CVE-2026-0265-check.py gp.customer.example | jq .
{
  "target": "https://gp.customer.example",
  "verdict": "VULNERABLE",
  "panos_version": "11.1.6-h23",
  "prelogin_status": "Success",
  "http_status": 200,
  "notes": [
    "11.1.6-h23 is below the advisory's patched hotfix for this base."
  ]
}

Sweep with low concurrency

gpsvc rate-limits under back-to-back probing — the script already retries each HTTP 503 with growing backoff, but -c 5 and a moderate -t is friendly to large fleets:

cat all-targets.txt | python3 CVE-2026-0265-check.py -b -c 5

Preconditions

The script can produce a determined verdict only when:

• The target is reachable from the operator's vantage point.
• The target is a PAN-OS GlobalProtect portal (responses from non-PAN-OS hosts resolve to NOT-AFFECTED-NOT-GLOBALPROTECT or UNDETERMINED-ERROR).
• The prelogin response is not gated by mTLS (otherwise UNDETERMINED-MTLS-GATED) or by an aggressive User-Agent check (otherwise UNDETERMINED-VERSION-GATED).

License

Distributed under an MIT license.

Legal Disclaimer

Usage of this tool for attacking targets without prior mutual consent is illegal. It is the end user's responsibility to obey all applicable local, state, and federal laws. The developers assume no liability and are not responsible for any misuse or damage caused by this program.

See Also

• Bishop Fox Blog
• Palo Alto Networks Advisory CVE-2026-0265
• NVD — CVE-2026-0265