9.8

CVE-2026-0300: Palo Alto Networks PAN-OS Out-of-bounds Write Vulnerability

CVSS: 9.8v3.1CriticalKEVAnalyzed
Published 06-05-2026Last modified 15-10-2026
Open JSON

Vulnerability summary

CVE-2026-0300 is a critical (CVSS 9.8) Out-of-bounds Write vulnerability in Palo Alto Networks PAN-OS. It is known to be exploited: CISA lists it, first on 06-05-2026. EPSS estimates a 31.72% chance of exploitation in the next 30 days, higher than 98.2% of scored vulnerabilities.

Overall risk
85/100
0100
Critical · default modelHow is this calculated?
CVSS score
9.8/10
010
Critical · v3.1 (NVD)
EPSS score
31.72%
0%100%
High · 0.00 pp in 30 days
KEVListedCISA
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Timeline

  1. 06-05-2026
    PublishedVulnerability first disclosed.
  2. 06-05-2026
    Added to CISA KEVPalo Alto Networks PAN-OS Out-of-bounds Write Vulnerability
  3. 09-05-2026
    CISA remediation dueApply mitigations per vendor instructions.
  4. 15-10-2026
    Last modifiedVulnerability information updated.

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.

CVSS metrics

3 scores · 2 sources · 2 versions

EPSS trend

Probability

31.72%

Chance of exploitation in the next 30 days

Percentile

98%

Versus all other CVEs

30-day change

0.00 pp

From 31.72% on 21-09-2026

21-09-202621-10-2026
EPSS score
31.72%

Known exploited

Compare KEV catalogs
CISA KEVListed
Added
06-05-2026
Federal due date
09-05-2026

CISA required action

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. security.paloaltonetworks.com/CVE-2026-0300 nvd.nist.gov/vuln/detail/CVE-2026-0300

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Palo alto networks1 product
  • pan-os≥ 12.1.0, < 12.1.7 | ≥ 11.2.0, < 11.2.12 | ≥ 11.1.0, < 11.1.15 | ≥ 10.2.0, < 10.2.18-h6
Paloaltonetworks1 product
  • pan-osEOL11.1.6:h7 | 11.1.7 | 11.1.7:h1 | 11.1.7:h2 | 11.1.7:h4 | 11.1.8 | 11.1.9 | 11.1.10 | 11.1.10:h1 | 11.1.10:h10 | 11.1.10:h12 | 11.1.10:h21 | 11.1.10:h4 | 11.1.10:h5 | 11.1.10:h7 | 11.1.10:h9 | 11.1.11 | 11.1.12 | 11.1.13 | 11.1.13:h1 | 11.1.13:h2 | 11.1.13:h3 | 11.1.14 | 11.2.0 | 11.2.1 | 11.2.2 | 11.2.3 | 11.2.4 | 11.2.4:h1 | 11.2.4:h10 | 11.2.4:h11 | 11.2.4:h12 | 11.2.4:h14 | 11.2.4:h15 | 11.2.4:h2 | 11.2.4:h4 | 11.2.4:h5 | 11.2.4:h6 | 11.2.4:h7 | 11.2.4:h8 | 11.2.4:h9 | 11.2.5 | 11.2.6 | 11.2.7 | 11.2.7:h1 | 11.2.7:h10 | 11.2.7:h11 | 11.2.7:h12 | 11.2.7:h2 | 11.2.7:h3 | 11.2.7:h4 | 11.2.7:h7 | 11.2.7:h8 | 11.2.8 | 11.2.9 | 11.2.10 | 11.2.10:h1 | 11.2.10:h2 | 11.2.10:h3 | 11.2.10:h4 | 11.2.10:h5 | 11.2.11 | 12.1.2 | 12.1.3 | 12.1.4 | 12.1.4:h2 | 12.1.4:h3 | 12.1.5 | 12.1.6 | 10.2.0 | 10.2.1 | 10.2.2 | 10.2.3 | 10.2.4 | 10.2.5 | 10.2.6 | 10.2.7 | 10.2.7:h1 | 10.2.7:h12 | 10.2.7:h16 | 10.2.7:h19 | 10.2.7:h21 | 10.2.7:h24 | 10.2.7:h3 | 10.2.7:h32 | 10.2.7:h6 | 10.2.7:h8 | 10.2.8 | 10.2.9 | 10.2.10 | 10.2.10:h10 | 10.2.10:h12 | 10.2.10:h14 | 10.2.10:h17 | 10.2.10:h18 | 10.2.10:h2 | 10.2.10:h21 | 10.2.10:h27 | 10.2.10:h3 | 10.2.10:h30 | 10.2.10:h31 | 10.2.10:h4 | 10.2.10:h5 | 10.2.10:h7 | 10.2.10:h9 | 10.2.11 | 10.2.12 | 10.2.13 | 10.2.13:h1 | 10.2.13:h10 | 10.2.13:h16 | 10.2.13:h18 | 10.2.13:h2 | 10.2.13:h3 | 10.2.13:h4 | 10.2.13:h5 | 10.2.13:h7 | 10.2.14 | 10.2.15 | 10.2.16 | 10.2.16:h1 | 10.2.16:h4 | 10.2.16:h6 | 10.2.17 | 10.2.18 | 10.2.18:h1 | 10.2.18:h5 | 11.1.0 | 11.1.1 | 11.1.2 | 11.1.3 | 11.1.4 | 11.1.4:h1 | 11.1.4:h13 | 11.1.4:h15 | 11.1.4:h16 | 11.1.4:h17 | 11.1.4:h18 | 11.1.4:h25 | 11.1.4:h27 | 11.1.4:h32 | 11.1.4:h4 | 11.1.4:h7 | 11.1.4:h9 | 11.1.5 | 11.1.6 | 11.1.6:h1 | 11.1.6:h10 | 11.1.6:h14 | 11.1.6:h17 | 11.1.6:h19 | 11.1.6:h2 | 11.1.6:h20 | 11.1.6:h21 | 11.1.6:h22 | 11.1.6:h23 | 11.1.6:h25 | 11.1.6:h29 | 11.1.6:h3 | 11.1.6:h4 | 11.1.6:h5 | 11.1.6:h6
Siemens1 product

3 vendors · 3 products

References

3 links