Palo Alto Networks PAN-OS Out-of-bounds Write Vulnerability
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…
Severity = CVSS. Probability = EPSS (FIRST). Exploitation = public signals: KEV, EUVD, ransomware, EPSS above 10 %, no account required.
Exploitation probability EPSS · FIRST
Exploitation signals 4 / 5
- KEV catalog (CISA)06 May 2026
- Exploited in EUVD (ENISA)06 May 2026
- Used by ransomwareno
- EPSS above 10 %41.7%
- No account, over the networkyes
What to do
Fix
Apply the vendor’s fix as soon as it is available.
CISA guidance: 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.
Meanwhile
Take the service off the internet or restrict access to it, watch the logs and look for signs of compromise.
Manufacturers (CRA)
Exploited vulnerability in your product: early warning to ENISA within 24 h, then notification within 72 h (Article 14 of the Cyber Resilience Act). The CRA explained
Description ENISA EUVD
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
- 11.1.0 <11.1.15
- 12.1.0 <12.1.7
- 11.2.0 <11.2.12
- 10.2.0 <10.2.18-h6
Open source packages OSV
Affected libraries according to OSV, with fixed versions.
Timeline
-
Published
-
Exploitation reported (ENISA)
-
Added to the KEV catalog
-
CISA remediation due date
-
EPSS peak: 41.7%
References
Other exploited vulnerabilities from the same vendor
- CVE-2026-0322Palo Alto Networks PAN-OS Code Injection Vulnerability4.7 · Rising fast
- CVE-2026-0257Palo Alto Networks PAN-OS Authentication Bypass Vulnerability9.0 · Actively exploited
- CVE-2025-0111Palo Alto Networks PAN-OS File Read Vulnerability4.1 · Background exploitation
- CVE-2025-0108Palo Alto Networks PAN-OS Authentication Bypass Vulnerability8.9 · Background exploitation
- CVE-2024-3393Palo Alto Networks PAN-OS Malicious DNS Packet Vulnerability6.8 · Background exploitation
- CVE-2024-9474Palo Alto Networks PAN-OS Management Interface OS Command Injection Vulnerability8.0 · Background exploitation