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 products 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 patch CVE-2026-0300?

No patch has shipped for CVE-2026-0300 yet — track the paloaltonetworks 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 paloaltonetworks pan-os deployment and check each version against the affected-products list above. Because the exploit targets the running system rather than your application code, also watch for remote code execution at the network and runtime layer — O3 flags the exploit behaviour from runtime telemetry and egress traffic even before a vulnerable build is confirmed.

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

Cut exposure now: restrict the management/admin interface to trusted networks, segment the device, and apply the vendor's recommended configuration mitigations and any WAF/IPS signature. O3's runtime protection blocks the exploit chain at execution, holding the line on unpatched or end-of-life systems until you can patch.

How does O3 Security protect against CVE-2026-0300?

O3 detects and blocks CVE-2026-0300 exploitation at runtime: eBPF exploit-chain detection, plus L7 egress monitoring that catches the post-exploitation callback and severs the attacker's outbound channel.

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

No public exploit code has been indexed for CVE-2026-0300 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

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

CVE-2026-0300 has an EPSS (Exploit Prediction Scoring System) score of 32.1%, 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 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 June 17, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

CVE-2026-0300: PAN-OS Out-of-bounds Write (Critical 9.8)

EPSS Exploitation Probability

via FIRST.org ↗

32.1%probability of exploitation in next 30 days

Moderate Risk98th percentile-4.08%

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

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.

Affected Products

2 products · 163 configurations

OS

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

OS

ruggedcom ape1808 firmwaresiemens

all

Detection & mitigation playbook

Vendor / appliance

Detect
Inventory every paloaltonetworks pan-os deployment and check each version against the affected-products list above. Because the exploit targets the running system rather than your application code, also watch for remote code execution at the network and runtime layer — O3 flags the exploit behaviour from runtime telemetry and egress traffic even before a vulnerable build is confirmed.
Remediation status
No patch has shipped for CVE-2026-0300 yet — track the paloaltonetworks pan-os advisory for a fixed release and apply the workarounds below in the meantime.
Mitigate without a patch
Cut exposure now: restrict the management/admin interface to trusted networks, segment the device, and apply the vendor's recommended configuration mitigations and any WAF/IPS signature. O3's runtime protection blocks the exploit chain at execution, holding the line on unpatched or end-of-life systems until you can patch.
How O3 protects you
O3 detects and blocks CVE-2026-0300 exploitation at runtime: eBPF exploit-chain detection, plus L7 egress monitoring that catches the post-exploitation callback and severs the attacker's outbound channel.

Tailored to CVE-2026-0300. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

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?

O3's eBPF runtime sensors and L7 egress monitoring detect and block the CVE-2026-0300 exploit chain at execution — protecting unpatched and end-of-life systems until the vendor patch is applied.

Protect my workloads How runtime protection works

CVE-2026-0300

EPSS Exploitation Probability

Description

Affected Products

Detection & mitigation playbook

Detect

Remediation status

Mitigate without a patch

How O3 protects you

Frequently Asked Questions

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