How severe is CVE-2026-0300?

No CVSS score has been assigned to CVE-2026-0300 yet. Review the advisory details and affected package list to assess your exposure.

Which products are affected by CVE-2026-0300?

CVE-2026-0300 affects the following products: palo_alto_networks pan-os.

How do I patch CVE-2026-0300?

No patch has shipped for CVE-2026-0300 yet — track the palo_alto_networks pan-os advisory for a fixed release and apply the workarounds below in the meantime.

How do I detect CVE-2026-0300 across my infrastructure?

Inventory every palo_alto_networks pan-os deployment and check each version against the affected-products list above.

How do I mitigate CVE-2026-0300 if there is no patch (or I can't update yet)?

Constrain what reaches the vulnerable code: limit the size and shape of untrusted input, isolate the affected component in a sandboxed or least-privileged process, and enable the platform's memory-safety mitigations (ASLR, stack protector, hardened allocator) so an out-of-bounds access is more likely to fail closed than to be exploitable. Alongside that, restrict the management interface to trusted networks and apply the vendor's recommended configuration mitigations.

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

Yes. There are 3 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 31.7%, placing it in the 98th 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 warrants monitoring and prompt remediation.

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 palo_alto_networks pan-os (49 versions, e.g. 10.2.0, 10.2.1, 10.2.2…). 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 October 15, 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 · ACTIVELY EXPLOITED

CVE-2026-0300 — PAN-OS

CVE-2026-0300 is a Out-of-bounds Write vulnerability in palo_alto_networks pan-os. It is in CISA's Known Exploited Vulnerabilities catalog (added 2026-05-06) — treat it as actively exploited and patch now. No vendor fix is recorded yet; mitigation options are listed below.

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

Oct 15, 2026

Affected

1 product

Patched

See advisory

Exploits

3 known

Exploitation data as of Oct 23, 2026 · OSV.dev, NVD, CISA KEV, FIRST.org (EPSS)

Exploitation Status

Actively exploited in the wild

Confirmed by CISA's Known Exploited Vulnerabilities catalog on 2026-05-06. Federal agencies were required to remediate by 2026-05-09.
CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
A successful exploit gives an attacker total control of the affected component, not partial access.

Exploitation and automatability from CISA (KEV catalog and SSVC triage) for CVE-2026-0300.

EPSS Exploitation Probability

via FIRST.org ↗

31.7%probability of exploitation in next 30 days

Moderate Risk0.00%

Lower risk than most CVEs98th percentile — riskier than 98% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

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

1 product · 184 configurations

pan-ospalo_alto_networks

49 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

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

⭐ 22🍴 11Sep 2026

matad0r-maghribi/CVE-2026-0300-PANOS

Security Research and Proof-of-Concept (PoC) for CVE-2026-0300 : Unauthe

⭐ 4🍴 0Sep 2026

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

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

⭐ 3🍴 0Aug 2026

Detection & mitigation playbook

Vendor / appliance

Detect
Inventory every palo_alto_networks pan-os deployment and check each version against the affected-products list above.
Remediation status
No patch has shipped for CVE-2026-0300 yet — track the palo_alto_networks pan-os advisory for a fixed release and apply the workarounds below in the meantime.
Mitigate without a patch
Constrain what reaches the vulnerable code: limit the size and shape of untrusted input, isolate the affected component in a sandboxed or least-privileged process, and enable the platform's memory-safety mitigations (ASLR, stack protector, hardened allocator) so an out-of-bounds access is more likely to fail closed than to be exploitable. Alongside that, restrict the management interface to trusted networks and apply the vendor's recommended configuration mitigations.

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 · Runtime Protection

Is CVE-2026-0300 being exploited in your environment?

Detect and block the exploit chain at execution, on systems you cannot patch yet.

Protect my workloads How runtime protection works