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CriticalKEV

CVE-2026-0300 — PAN-OS: Unauthenticated user initiated Buffer Overflow Vulnerability in User-ID™ Authentication Portal

CVE-2026-0300 · PAN-OS · CVSS 9.8 · KEV

In brief

Severity · CVSS
Critical9.8CVSS 3.1, Critical
EPSS
32%
CISA KEV
Known exploited, listed since 6 May 2026
Products
PAN-OS
Published · Modified
·
Last verified

Summary

A buffer overflow vulnerability in the User-ID™ Authentication Portal (aka Captive Portal) service of Palo Alto Networks PAN-OS software allows an unauthenticated attacker to execute arbitrary code with root privileges on the PA-Series and VM-Series firewalls by sending specially crafted packets. The risk of this issue is greatly reduced if you secure access to the User-ID™ Authentication Portal per the best practice guidelines https://knowledgebase.paloaltonetworks.com/KCSArticleDetail by restricting access to only trusted internal IP addresses. Prisma Access, Cloud NGFW and Panorama appliances are not impacted by this vulnerability.

Weakness: CWE-787

Title, description and the vendor's statements are quoted from the CVE record; a vendor's advisory is summarised in Patcharo's words, with a link.

Affected and fixed versions

Per product and release branch, as the vendor's CVE record and official advisory state them. A fixed release is shown only when a document names it: the vendor's, or CERT-FR's for Check Point, with its source.

4 branches with a published fixed release

Palo Alto Networks PAN-OS

Source: CVE-2026-0300

  1. 12.1
    Affected versions>= 12.1.0, < 12.1.4-h5>= 12.1.5, < 12.1.7
    First fixed release12.1.4-h512.1.7
  2. 11.2Approaching end of support
    Affected versions>= 11.2.0, < 11.2.4-h17>= 11.2.5, < 11.2.7-h13>= 11.2.8, < 11.2.10-h6>= 11.2.11, < 11.2.12
    First fixed release11.2.4-h1711.2.7-h1311.2.10-h611.2.12
  3. 11.1Approaching end of support
    Affected versions>= 11.1.0, < 11.1.4-h33>= 11.1.5, < 11.1.6-h32>= 11.1.7, < 11.1.7-h6>= 11.1.8, < 11.1.10-h25>= 11.1.11, < 11.1.13-h5>= 11.1.14, < 11.1.15
    First fixed release11.1.4-h3311.1.6-h3211.1.7-h611.1.10-h2511.1.13-h511.1.15
  4. 10.2End of life
    Affected versions>= 10.2.0, < 10.2.7-h34>= 10.2.8, < 10.2.10-h36>= 10.2.11, < 10.2.13-h21>= 10.2.14, < 10.2.16-h7>= 10.2.17, < 10.2.18-h6
    First fixed release10.2.7-h3410.2.10-h3610.2.13-h2110.2.16-h710.2.18-h6

Releases the vendor does not list are not affected.

Remediation

Fix available

Vendor fix

  • PAN-OS 12.112.1.4-h5, 12.1.7
  • PAN-OS 11.211.2.4-h17, 11.2.7-h13, 11.2.10-h6, 11.2.12
  • PAN-OS 11.111.1.4-h33, 11.1.6-h32, 11.1.7-h6, 11.1.10-h25, 11.1.13-h5, 11.1.15
  • PAN-OS 10.210.2.7-h34, 10.2.10-h36, 10.2.13-h21, 10.2.16-h7, 10.2.18-h6

Upgrade to a fixed release listed above for your branch, or to a later fixed release the vendor explicitly supports.

This issue will be fixed in upcoming releases of PAN-OS as captured in the table above. We strongly recommend that you secure access to your User-ID™ Authentication Portal following the instructions in the workarounds section below.

SourcePalo Alto Networks (CVE record)

Mitigation (vendor)

Customers can mitigate the risk of this issue by taking either of the following actions: * Restrict User-ID™ Authentication Portal access to only trusted zones and in addition, disable Response Pages in the Interface Management Profile attached to every L3 interface in any zone where untrusted/internet traffic can

Full text

ingress. Keep Response Pages enabled only on interfaces in trust/internal zones where legitimate users' browsers ingress. Refer to Step 6 of the following Live Community article (https://live.paloaltonetworks.com/t5/general-articles/why-it-s-essential-to-secure-your-management-interface/ta-p/1001286) and Knowledgebase article (https://knowledgebase.paloaltonetworks.com/KCSArticleDetail?id=kA14u000000CqbiCAC) for steps to restrict access. * Disable User-ID™ Authentication Portal if not required. Customers with a Threat Prevention subscription can block attacks for this vulnerab…

SourcePalo Alto Networks (CVE record)

CISA KEV required action

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Full CISA action

Until the vendor releases an official fix, the following workaround should be implemented: - Restrict User-ID Authentication Portal access to only trusted zones. - Disable User-ID Authentication Portal if not required. 5/13/2026: Palo Alto has released a variety of patches. If these are relevant to your environment, please apply the designated patch.

CISA due date:

SourceCISA KEV

CERT-FR recommendation

Refer to the vendor's security bulletin to obtain patches (see Documentation section).

SourceCERTFR-2026-AVI-0537

Last verified 1 Oct 2026 at 09:32 UTC

Known exploitation

Added to CISA KEV on 6 May 2026

Federal remediation due date: 9 May 2026

The CISA required action is shown under Remediation.

32% probability of exploitation in the next 30 days (percentile 98%).

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CERT-FR

1 document of the French national CERT (ANSSI) references this CVE.

Advisory (AVI)CERTFR-2026-AVI-0537Published 6 May 2026

Vulnerability in Palo Alto Networks User-ID Authentication Portal

Remote arbitrary code execution

Summary

A vulnerability has been discovered in Palo Alto Networks User-ID Authentication Portal. It allows an attacker to cause remote arbitrary code execution. Palo Alto Networks indicates that vulnerability CVE-2026-0300 is being actively exploited. The vendor indicates that patches will be published on May 13 and May 28, 2026.

Recommendation

Refer to the vendor's security bulletin to obtain patches (see Documentation section).

Official document on cert.ssi.gouv.frread by Patcharo 28 Sept 2026 at 20:03 UTCMachine translation of the French text published by CERT-FR; a text whose translation did not pass Patcharo's checks stays in French. Identifiers, versions and links are copied unchanged.

Timeline

  1. Added to CISA KEV
  2. Published by the source
  3. CISA remediation due date
  4. Source record last modified
  5. EPSS score computed
  6. Last verified by Patcharo

Official sources

Vendor advisory

References

Palo Alto Networks · CISA Known Exploited Vulnerabilities · NVD · FIRST EPSS

How Patcharo reads this

Affected and fixed releases come from the vendor's structured statements and are matched against exact versions; CVSS from NVD, exploitation from CISA KEV and the vendor's own advisory, probability from FIRST EPSS. Missing data stays Unknown and never becomes Not affected.

Read the methodologyRead the guide: PAN-OS versions explained: release lines, maintenance releases and the -h1, -h2, -h3 suffixes

Related vulnerabilities

Other records affecting the same products, newest first.

  • CVE-2026-0301PAN-OS: Information Disclosure Vulnerability in URL FilteringHigh
  • CVE-2026-0280PAN-OS: IPv6 Firewall Policy BypassHigh
  • CVE-2026-0281PAN-OS: Information Disclosure Vulnerability in Management Web InterfaceHigh
  • CVE-2026-0283PAN-OS: Authentication Bypass Vulnerability in Large Scale VPN (LSVPN)High
  • CVE-2026-0284PAN-OS: XML Injection Vulnerability in Large Scale VPN (LSVPN)Critical

All PAN-OS vulnerabilitiesAll Palo Alto Networks vulnerabilities