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Palo Alto Networks disclosed CVE-2026-0300, a critical CWE-787 out-of-bounds write in the PAN-OS User-ID Authentication Portal, also known as the Captive Portal, that allows an unauthenticated attacker to achieve remote code execution as root on affected PA-Series and VM-Series firewalls. The flaw was reported as actively exploited in the wild and added to CISA's Known Exploited Vulnerabilities catalog, with exploitation observed against portals reachable from untrusted networks or the public internet. Palo Alto said Prisma Access, Cloud NGFW, and Panorama are not affected, while vulnerable PAN-OS branches included 10.2, 11.1, 11.2, and 12.1 below fixed releases.
Reporting on observed intrusions said attackers used the firewall access for shellcode injection into nginx worker processes, credential extraction, Active Directory enumeration, outbound tunneling with tools such as EarthWorm and ReverseSocks5, internal pivoting, and anti-forensic log cleanup. Palo Alto began releasing patches in staged waves and urged defenders to disable the Captive Portal if unused or restrict it to trusted IPs and zones, enable available threat-prevention signatures, and treat previously exposed devices as potentially fully compromised by auditing configurations, checking admin accounts and SSH keys, rotating credentials, and monitoring for persistence or suspicious outbound connections.
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6 events from the most recent confirmed update back to the earliest known activity.
Palo Alto Networks began releasing patches for CVE-2026-0300 in staged waves starting on May 13, 2026, for affected PAN-OS branches. The company continued to recommend restricting Authentication Portal access to trusted zones or disabling the feature until systems were fully remediated.
At disclosure, Palo Alto said fixes were not yet available but published estimated release dates for patched PAN-OS versions. Reporting said the first wave of patches would begin on May 13, 2026, followed by a second wave on May 28, 2026.
On May 6, 2026, CISA added CVE-2026-0300 to its Known Exploited Vulnerabilities catalog due to active exploitation. The listing set a remediation deadline of May 9, 2026 for affected federal agencies.
On May 6, 2026, Palo Alto Networks disclosed CVE-2026-0300 as a critical unauthenticated out-of-bounds write / buffer overflow in the PAN-OS User-ID Authentication Portal that can lead to root-level remote code execution on affected PA-Series and VM-Series firewalls. The vendor said the flaw was being actively exploited in the wild and advised restricting or disabling the Captive Portal where possible.
By April 16, 2026, attackers had achieved remote code execution as root via CVE-2026-0300. Reported follow-on activity included shellcode injection into nginx worker processes, credential extraction, Active Directory enumeration, anti-forensic log cleanup, and outbound tunneling with tools such as EarthWorm and ReverseSocks5.
Palo Alto Networks and Unit 42 observed limited in-the-wild exploitation of CVE-2026-0300 starting on April 9, 2026, targeting PAN-OS User-ID Authentication Portals exposed to untrusted networks or the public internet.
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Palo Alto Networks disclosed **CVE-2026-0300**, a critical `CWE-787` buffer overflow in the PAN-OS User-ID Authentication Portal (Captive Portal) that allows **unauthenticated remote code execution as root** on affected **PA-Series** and **VM-Series** firewalls. The flaw carries a **CVSS v4 score of 9.3** when the portal is exposed to untrusted networks or the public internet, and Palo Alto confirmed limited in-the-wild exploitation against exposed portals. Affected versions span PAN-OS 10.2, 11.1, 11.2, and 12.1, while **Prisma Access, Cloud NGFW, and Panorama are not affected**. With patches not immediately available at disclosure, Palo Alto said fixed releases would begin rolling out between May 13 and May 28 and urged customers to restrict portal access to trusted internal zones or disable the feature entirely; the company also released a Threat Prevention Signature for PAN-OS 11.1 and later. U.S. **CISA** added the vulnerability to its **Known Exploited Vulnerabilities** catalog and ordered federal civilian agencies to remediate by the mandated deadline, while other national and regional cyber authorities issued parallel alerts. Palo Alto Unit 42 and multiple reports linked the activity to a likely state-sponsored cluster tracked as **CL-STA-1132**, which reportedly probed targets for weeks, injected shellcode into an `nginx` worker process, deleted crash artifacts and logs, enumerated Active Directory through firewall-linked service accounts, and used **EarthWorm** and **ReverseSocks5** tunnels for command and control and lateral movement. Researchers warned that thousands of internet-exposed PAN-OS instances remain reachable, making perimeter firewalls with exposed Captive Portal services high-priority compromise candidates.
Jun 29, 2026
Palo Alto Networks disclosed and patched **CVE-2026-0300**, a critical `PAN-OS` vulnerability in the **User-ID Authentication Portal** that can let an unauthenticated remote attacker execute arbitrary code with **root** privileges. The flaw, rated **CVSS 9.3**, is described as a stack overflow and out-of-bounds write issue affecting multiple `PAN-OS` release lines, including versions in the `10.2`, `11.1`, `11.2`, and `12.1` branches, on affected **PA Series** and **VM-Series** firewalls. Palo Alto Networks reported signs of **active exploitation**, particularly on devices exposed to the internet or reachable from untrusted IP addresses, and **CISA** added the bug to its **Known Exploited Vulnerabilities** catalog. Exploitation depends on the Authentication Portal being enabled and a management interface profile with a response page being attached to a Layer 3 interface reachable by untrusted traffic; defenders were urged to upgrade to fixed releases, restrict portal access to trusted zones or IP addresses, disable the feature if unnecessary, and investigate systems for signs of compromise.
Jul 23, 2026
Palo Alto Networks disclosed and patched multiple vulnerabilities in **PAN-OS** affecting **PA-Series**, **VM-Series**, and **Panorama**, including `CVE-2026-0273`, an authenticated administrator command injection flaw in the **CLI** and **web management interface** that can allow arbitrary commands to run as **root**. The vendor also fixed `CVE-2026-0272`, an authenticated **CLI privilege escalation** issue, and `CVE-2026-0266`, a **stored XSS** vulnerability in the web interface. A separate issue, `CVE-2026-0269`, can trigger a **denial of service** through crafted tunnel traffic and repeatedly reboot affected firewalls, potentially forcing them into maintenance mode. Affected versions span supported **PAN-OS 12.1, 11.2, 11.1, and 10.2** release trains, while **Cloud NGFW** and **Prisma Access** were reported as unaffected. Palo Alto Networks said it was not aware of active exploitation at disclosure time and urged customers to upgrade promptly, restrict management access to trusted internal IPs, limit CLI exposure, and use hardened jump boxes; for `CVE-2026-0273`, organizations with **Threat Prevention** can also enable dedicated **Threat IDs** to help block exploit attempts when management traffic is inspectable and decrypted.
Jun 29, 2026