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Exploited vulnerability · CISA KEV

Is CVE-2026-0300 exploited? Yes: in CISA KEV since 6 May 2026

Gociux · Palo Alto Networks PAN-OS · data: CISA KEV, CVE record, FIRST EPSS

Yes. CVE-2026-0300, Palo Alto Networks PAN-OS Out-of-bounds Write Vulnerability, is being exploited in the wild. CISA added it to its Known Exploited Vulnerabilities catalog on 6 May 2026, the day it was published. It affects Palo Alto Networks PAN-OS, an internet-facing product of the kind attackers use for initial access. If you run it, CISA's required action is: 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.

exploitedYesCISA KEV · 6 May 2026
ransomwareNot knownno confirmed use
EPSStop 5%very likely to be exploited
severity9.3CVSS 4.0 · critical
US federal due9 May 2026BOD 22-01 deadline

What it is

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.

VendorPalo Alto Networks (16 exploited CVEs in KEV)
ProductPAN-OS
VulnerabilityPalo Alto Networks PAN-OS Out-of-bounds Write Vulnerability
WeaknessCWE-787
Published6 May 2026
Added to KEV6 May 2026
Reported by (CNA)palo_alto

What to do

  1. Check whether you run it. Look for PAN-OS in your asset inventory, including appliances and cloud images. Stack check lists every exploited Palo Alto Networks CVE at once.
  2. Apply the fix. 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.
  3. If you can't patch today, take the affected service off the internet or restrict who can reach it, and check its logs for signs of compromise since 6 May 2026.
  4. Get told next time. Email alerts when CISA adds a CVE for Palo Alto Networks.

Other exploited CVEs in PAN-OS

References

Questions

Is CVE-2026-0300 being exploited?

Yes. CISA added CVE-2026-0300 to the Known Exploited Vulnerabilities catalog on 6 May 2026, which means there is reliable evidence of exploitation in the wild.

Is CVE-2026-0300 used in ransomware attacks?

CISA does not list known ransomware use for it. That can change, and exploitation alone is reason to fix it first.

How do I fix CVE-2026-0300?

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. Check Palo Alto Networks's advisory for the fixed versions, and if you can't patch quickly, restrict access to the affected PAN-OS and watch it for signs of compromise.

Sources: CISA KEV (exploitation, ransomware use, required action, due date), the CVE record (publication date, CVSS, CNA), NVD and FIRST EPSS (live score). More: all KEV additions in May 2026 · Palo Alto Networks scorecard · act-now radar.

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