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CVE-2026-0300: Palo Alto Networks PAN-OS Out-of-bounds Write Vulnerability

criticalknown exploitedpublic exploitCVE-2026-0300
Actively exploited. At least one CVE in this advisory is listed in the CISA Known Exploited Vulnerabilities catalog — exploitation has been observed in the wild. Treat remediation as urgent.
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.

CSIRTS triage

vendor: Palo Alto Networksproduct: PAN-OSRemote code execution
What
Palo Alto Networks PAN-OS contains an out-of-bounds write vulnerability that can allow an unauthenticated attacker to execute arbitrary code with root privileges.
Who is affected
Users of PA-Series and VM-Series firewalls are affected.
Urgency
Remediation is urgent due to the critical nature of the vulnerability and its exploitation status.
Action
Users should apply the latest patches provided by Palo Alto Networks.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source
CISA Known Exploited Vulnerabilities (US · database · site)
Severity
critical
Published
2026-05-06
Exploitation
Observed in the wild (CISA KEV)

Original advisory: https://nvd.nist.gov/vuln/detail/CVE-2026-0300

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Referenced CVEs

CVECSIRTS overviewExternal
CVE-2026-0300coverage & exploitation statusNVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

Recent advisories for Palo Alto Networks

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

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