How severe is CVE-2026-0300?

CVE-2026-0300 has a CVSS score of 9.8/10, rated CRITICAL. Immediate patching is strongly recommended.

Which packages are affected by CVE-2026-0300?

Affected package information for CVE-2026-0300 is not yet fully mapped. Check the official advisory links for details.

How do I fix CVE-2026-0300?

No fixed version has been published for CVE-2026-0300 yet. Monitor the advisory for updates, apply mitigations recommended by the vendor, and use O3 Security to track when a fix becomes available in your stack.

Is CVE-2026-0300 actively exploited in the wild?

Yes. There are 2 known exploit references for CVE-2026-0300, including . All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2026-0300?

CVE-2026-0300 has an EPSS (Exploit Prediction Scoring System) score of 4.9%, placing it in the 90th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

Is CVE-2026-0300 in the CISA Known Exploited Vulnerabilities catalog?

Yes. CVE-2026-0300 (Palo Alto Networks PAN-OS Out-of-bounds Write Vulnerability) was added to CISA's Known Exploited Vulnerabilities (KEV) catalog on 2026-05-06. CISA required all US federal civilian agencies to remediate this vulnerability by 2026-05-09. The required action was: 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. Being listed in the KEV catalog is the strongest possible confirmation of active exploitation — treat this as a critical priority.

What type of vulnerability is CVE-2026-0300?

CVE-2026-0300 is classified as Out-of-bounds Write (CWE-787). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

Which products and versions are affected by CVE-2026-0300?

CVE-2026-0300 affects paloaltonetworks pan-os (51 versions, e.g. 10.2.0, 10.2.1, 10.2.2…); siemens ruggedcom ape1808 firmware. Check the affected-products list on this page against your deployed version to confirm exposure.

When was CVE-2026-0300 published, and has it been updated?

CVE-2026-0300 was published on May 6, 2026 and was last updated on May 12, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

CISA KEV·Added 2026-05-06 — agencies required to remediate by 2026-05-09

CVE-2026-0300

CRITICAL

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…

Published

May 6, 2026

Updated

May 12, 2026

Affected

0 pkgs

Patched

None yet

Exploits

2 known

EPSS Exploitation Probability

via FIRST.org ↗

4.9%probability of exploitation in next 30 days

Lower Risk90th percentile+0.38%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Description

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.

Affected Products

2 products · 163 configurations

pan-ospaloaltonetworks

51 versions

10.2.010.2.110.2.210.2.310.2.410.2.510.2.610.2.710.2.810.2.910.2.1010.2.11

ruggedcom ape1808 firmwaresiemens

all

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

p3Nt3st3r-sTAr/CVE-2026-0300-POC

⭐ 19🍴 11Jun 2026

qassam-315/PAN-OS-User-ID-Buffer-Overflow-PoC

A research-grade Proof-of-Concept (PoC) for CVE-2026-0300, targeting the

⭐ 3🍴 0May 2026

Frequently Asked Questions

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 app

O3 Security · Impact-Aware SCA

Is CVE-2026-0300 in your stack?

O3 detects CVE-2026-0300 across dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

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