Skip to content

CVE-2026-0300

Out-of-bounds Write — is CVE-2026-0300real, exploitable, or a false positive? Here's the community ground truth.

☆ Watch
Critical · CVSS 9.8EPSS 31.8%CISA KEVCWE-787 · Out-of-bounds Write

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

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.

References

NVD MITRE CVE.org CISA KEV

Published

Embed this verdict
TruePositive verdict for CVE-2026-0300
Markdown
[![TruePositive verdict](https://www.truepositive.app/cve/CVE-2026-0300/badge.svg)](https://www.truepositive.app/cve/CVE-2026-0300)
HTML
<a href="https://www.truepositive.app/cve/CVE-2026-0300"><img src="https://www.truepositive.app/cve/CVE-2026-0300/badge.svg" alt="TruePositive verdict for CVE-2026-0300"></a>

Live badge — updates automatically as the community verdict changes.

Community ground truth

Community verdict

2 verdicts
Not a real issue

Includes TruePositive's curated baseline from public sources — community verdicts accrue on top.

to add your verdict.

Community real-world severity: Critical (Critical 2) — CVSS base score 9.8

In line with its CVSS base score.

Field notes & remediation

Verdicts are the quick signal — notes are the evidence and fixes behind them.

  • 0
    Field note · Tomáš NovákCurated

    Palo Alto Networks PAN-OS Out-of-bounds Write Vulnerability — Palo Alto Networks PAN-OS contains an out-of-bounds write vulnerability in the User-ID Authentication Portal (aka Captive Portal) service that can allow an unauthenticated attacker to execute arbitrary code with root privileges on the PA-Series and VM-Series firewalls by sending specially crafted packets. Listed in the CISA KEV catalog (added 2026-05-06) — confirmed exploited in the wild, not theoretical. FIRST EPSS puts the chance of exploitation in the next 30 days at ~32%. Treat it as real and prioritize remediation over triage.

  • 0
    Remediation · Lin WeiCurated

    Required action for Palo Alto Networks PAN-OS: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. 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 set a federal remediation due date of 2026-05-09. After patching, verify the vulnerable path is no longer reachable before closing the finding.

Related CVEs

Same weakness — CWE-787 · Out-of-bounds Write.