CVE-2026-0300 | PAN-OS: Unauthenticated user initiated Buffer Overflow Vulnerability in User-ID™ Authentication Portal

Exp

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.

Published: 2026-05-06 Last update: 2026-05-12 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-0300 is rated Critical Active Threat (93.6/100): CVSS Critical severity, with medium exploitation likelihood (EPSS 4.54%). CISA KEV confirms active exploitation (added 2026-05-06) affecting Palo Alto Networks / PAN-OS. a weakness (CWE-787) Unauthenticated remote administrative access may be possible. The CISA remediation deadline has passed—treat as an emergency patch priority.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

CISA KEV Record for CVE-2026-0300

Name: Palo Alto Networks PAN-OS Out-of-bounds Write Vulnerability · CISA KEV detail

Exploit added: 2026-05-06

Action due: 2026-05-09

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.

Exploit prediction scoring system (EPSS) score for CVE-2026-0300

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-05-27 4.35% 4.54% +0.18%
2 2026-05-22 14.43% 4.35% -10.08%
3 2026-05-13 — 14.43% —

Full EPSS history (7 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-0300

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
9.3 4.0 CRITICAL
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:L/SI:L/SA:N/E:A/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:Y/R:U/V:C/RE:M/U:Red Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network.
Attack complexity (AC:L)
Exploitation conditions are straightforward and stable.
Attack requirements (AT:N)
No additional preconditions are required beyond normal reachability.
Privileges required (PR:N)
No privileges are required.
User interaction (UI:N)
No user interaction is required.
Vulnerable system confidentiality impact (VC:H)
High confidentiality impact on the vulnerable system.
Vulnerable system integrity impact (VI:H)
High integrity impact on the vulnerable system.
Vulnerable system availability impact (VA:H)
High availability impact on the vulnerable system.
Subsequent system confidentiality impact (SC:L)
Limited confidentiality impact on subsequent systems.
Subsequent system integrity impact (SI:L)
Limited integrity impact on subsequent systems.
Subsequent system availability impact (SA:N)
No availability impact on subsequent systems.
Exploit maturity (threat) (E:A)
Attacked: exploitation has been reported, or toolkits exist that simplify exploitation.
Confidentiality requirement (CR:X)
Not defined: insufficient information; scoring treats this like High (worst case).
Integrity requirement (IR:X)
Not defined: insufficient information; scoring treats this like High (worst case).
Availability requirement (AR:X)
Not defined: insufficient information; scoring treats this like High (worst case).
Modified attack vector (MAV:X)
Not defined: scoring uses the Base Attack Vector (AV).
Modified attack complexity (MAC:X)
Not defined: scoring uses the Base Attack Complexity (AC).
Modified attack requirements (MAT:X)
Not defined: scoring uses the Base Attack Requirements (AT).
Modified privileges required (MPR:X)
Not defined: scoring uses the Base Privileges Required (PR).
Modified user interaction (MUI:X)
Not defined: scoring uses the Base User Interaction (UI).
Modified vulnerable system confidentiality impact (MVC:X)
Not defined: scoring uses the Base VC metric.
Modified vulnerable system integrity impact (MVI:X)
Not defined: scoring uses the Base VI metric.
Modified vulnerable system availability impact (MVA:X)
Not defined: scoring uses the Base VA metric.
Modified subsequent system confidentiality impact (MSC:X)
Not defined: scoring uses the Base SC metric.
Modified subsequent system integrity impact (MSI:X)
Not defined: scoring uses the Base SI metric.
Modified subsequent system availability impact (MSA:X)
Not defined: scoring uses the Base SA metric.
Safety (supplemental) (S:X)
Not evaluated.
Automatable (supplemental) (AU:Y)
Yes: all four kill-chain steps (reconnaissance, weaponization, delivery, exploitation) can be automated.
Recovery (supplemental) (R:U)
User: manual user intervention is needed to recover services.
Value density (supplemental) (V:C)
Concentrated: a single exploit event controls rich resources (e.g., a central server).
Vulnerability response effort (supplemental) (RE:M)
Moderate effort (remote update, disable subsystem, simple upgrade with minor service impact).
Provider urgency (supplemental) (U:RED)
Red: provider rates highest urgency.
 — — [email protected]
9.8 3.1 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 5.9 [email protected]

Weakness enumeration for CVE-2026-0300

GitHub Security Advisory for CVE-2026-0300

GHSA-3vfh-3cpw-2378 · Severity: critical — A buffer overflow vulnerability in the User-ID™ Authentication Portal (aka Captive Portal)...

Affected software / configurations for CVE-2026-0300

Vendor Product Version Raw CPE
paloaltonetworks pan-os 10.2.0 cpe:2.3:o:paloaltonetworks:pan-os:10.2.0:*:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.1 cpe:2.3:o:paloaltonetworks:pan-os:10.2.1:*:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.2 cpe:2.3:o:paloaltonetworks:pan-os:10.2.2:*:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.3 cpe:2.3:o:paloaltonetworks:pan-os:10.2.3:*:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.4 cpe:2.3:o:paloaltonetworks:pan-os:10.2.4:*:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.5 cpe:2.3:o:paloaltonetworks:pan-os:10.2.5:*:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.6 cpe:2.3:o:paloaltonetworks:pan-os:10.2.6:*:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.7 cpe:2.3:o:paloaltonetworks:pan-os:10.2.7:-:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.7 cpe:2.3:o:paloaltonetworks:pan-os:10.2.7:h1:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.7 cpe:2.3:o:paloaltonetworks:pan-os:10.2.7:h12:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.7 cpe:2.3:o:paloaltonetworks:pan-os:10.2.7:h16:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.7 cpe:2.3:o:paloaltonetworks:pan-os:10.2.7:h19:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.7 cpe:2.3:o:paloaltonetworks:pan-os:10.2.7:h21:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.7 cpe:2.3:o:paloaltonetworks:pan-os:10.2.7:h24:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.7 cpe:2.3:o:paloaltonetworks:pan-os:10.2.7:h3:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.7 cpe:2.3:o:paloaltonetworks:pan-os:10.2.7:h32:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.7 cpe:2.3:o:paloaltonetworks:pan-os:10.2.7:h6:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.7 cpe:2.3:o:paloaltonetworks:pan-os:10.2.7:h8:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.8 cpe:2.3:o:paloaltonetworks:pan-os:10.2.8:*:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.9 cpe:2.3:o:paloaltonetworks:pan-os:10.2.9:*:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.10 cpe:2.3:o:paloaltonetworks:pan-os:10.2.10:-:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.10 cpe:2.3:o:paloaltonetworks:pan-os:10.2.10:h10:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.10 cpe:2.3:o:paloaltonetworks:pan-os:10.2.10:h12:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.10 cpe:2.3:o:paloaltonetworks:pan-os:10.2.10:h14:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.10 cpe:2.3:o:paloaltonetworks:pan-os:10.2.10:h17:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.10 cpe:2.3:o:paloaltonetworks:pan-os:10.2.10:h18:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.10 cpe:2.3:o:paloaltonetworks:pan-os:10.2.10:h2:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.10 cpe:2.3:o:paloaltonetworks:pan-os:10.2.10:h21:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.10 cpe:2.3:o:paloaltonetworks:pan-os:10.2.10:h27:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.10 cpe:2.3:o:paloaltonetworks:pan-os:10.2.10:h3:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.10 cpe:2.3:o:paloaltonetworks:pan-os:10.2.10:h30:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.10 cpe:2.3:o:paloaltonetworks:pan-os:10.2.10:h31:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.10 cpe:2.3:o:paloaltonetworks:pan-os:10.2.10:h4:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.10 cpe:2.3:o:paloaltonetworks:pan-os:10.2.10:h5:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.10 cpe:2.3:o:paloaltonetworks:pan-os:10.2.10:h7:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.10 cpe:2.3:o:paloaltonetworks:pan-os:10.2.10:h9:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.11 cpe:2.3:o:paloaltonetworks:pan-os:10.2.11:*:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.12 cpe:2.3:o:paloaltonetworks:pan-os:10.2.12:*:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.13 cpe:2.3:o:paloaltonetworks:pan-os:10.2.13:-:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.13 cpe:2.3:o:paloaltonetworks:pan-os:10.2.13:h1:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.13 cpe:2.3:o:paloaltonetworks:pan-os:10.2.13:h10:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.13 cpe:2.3:o:paloaltonetworks:pan-os:10.2.13:h16:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.13 cpe:2.3:o:paloaltonetworks:pan-os:10.2.13:h18:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.13 cpe:2.3:o:paloaltonetworks:pan-os:10.2.13:h2:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.13 cpe:2.3:o:paloaltonetworks:pan-os:10.2.13:h3:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.13 cpe:2.3:o:paloaltonetworks:pan-os:10.2.13:h4:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.13 cpe:2.3:o:paloaltonetworks:pan-os:10.2.13:h5:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.13 cpe:2.3:o:paloaltonetworks:pan-os:10.2.13:h7:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.14 cpe:2.3:o:paloaltonetworks:pan-os:10.2.14:*:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.15 cpe:2.3:o:paloaltonetworks:pan-os:10.2.15:*:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.16 cpe:2.3:o:paloaltonetworks:pan-os:10.2.16:-:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.16 cpe:2.3:o:paloaltonetworks:pan-os:10.2.16:h1:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.16 cpe:2.3:o:paloaltonetworks:pan-os:10.2.16:h4:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.16 cpe:2.3:o:paloaltonetworks:pan-os:10.2.16:h6:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.17 cpe:2.3:o:paloaltonetworks:pan-os:10.2.17:-:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.18 cpe:2.3:o:paloaltonetworks:pan-os:10.2.18:-:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.18 cpe:2.3:o:paloaltonetworks:pan-os:10.2.18:h1:*:*:*:*:*:*
paloaltonetworks pan-os 10.2.18 cpe:2.3:o:paloaltonetworks:pan-os:10.2.18:h5:*:*:*:*:*:*
paloaltonetworks pan-os 11.1.0 cpe:2.3:o:paloaltonetworks:pan-os:11.1.0:*:*:*:*:*:*:*
paloaltonetworks pan-os 11.1.1 cpe:2.3:o:paloaltonetworks:pan-os:11.1.1:*:*:*:*:*:*:*
paloaltonetworks pan-os 11.1.2 cpe:2.3:o:paloaltonetworks:pan-os:11.1.2:*:*:*:*:*:*:*
paloaltonetworks pan-os 11.1.3 cpe:2.3:o:paloaltonetworks:pan-os:11.1.3:*:*:*:*:*:*:*
paloaltonetworks pan-os 11.1.4 cpe:2.3:o:paloaltonetworks:pan-os:11.1.4:-:*:*:*:*:*:*
paloaltonetworks pan-os 11.1.4 cpe:2.3:o:paloaltonetworks:pan-os:11.1.4:h1:*:*:*:*:*:*
paloaltonetworks pan-os 11.1.4 cpe:2.3:o:paloaltonetworks:pan-os:11.1.4:h13:*:*:*:*:*:*
paloaltonetworks pan-os 11.1.4 cpe:2.3:o:paloaltonetworks:pan-os:11.1.4:h15:*:*:*:*:*:*
paloaltonetworks pan-os 11.1.4 cpe:2.3:o:paloaltonetworks:pan-os:11.1.4:h16:*:*:*:*:*:*
paloaltonetworks pan-os 11.1.4 cpe:2.3:o:paloaltonetworks:pan-os:11.1.4:h17:*:*:*:*:*:*
paloaltonetworks pan-os 11.1.4 cpe:2.3:o:paloaltonetworks:pan-os:11.1.4:h18:*:*:*:*:*:*
paloaltonetworks pan-os 11.1.4 cpe:2.3:o:paloaltonetworks:pan-os:11.1.4:h25:*:*:*:*:*:*
paloaltonetworks pan-os 11.1.4 cpe:2.3:o:paloaltonetworks:pan-os:11.1.4:h27:*:*:*:*:*:*
paloaltonetworks pan-os 11.1.4 cpe:2.3:o:paloaltonetworks:pan-os:11.1.4:h32:*:*:*:*:*:*
paloaltonetworks pan-os 11.1.4 cpe:2.3:o:paloaltonetworks:pan-os:11.1.4:h4:*:*:*:*:*:*
paloaltonetworks pan-os 11.1.4 cpe:2.3:o:paloaltonetworks:pan-os:11.1.4:h7:*:*:*:*:*:*
paloaltonetworks pan-os 11.1.4 cpe:2.3:o:paloaltonetworks:pan-os:11.1.4:h9:*:*:*:*:*:*
paloaltonetworks pan-os 11.1.5 cpe:2.3:o:paloaltonetworks:pan-os:11.1.5:*:*:*:*:*:*:*
paloaltonetworks pan-os 11.1.6 cpe:2.3:o:paloaltonetworks:pan-os:11.1.6:-:*:*:*:*:*:*
paloaltonetworks pan-os 11.1.6 cpe:2.3:o:paloaltonetworks:pan-os:11.1.6:h1:*:*:*:*:*:*
paloaltonetworks pan-os 11.1.6 cpe:2.3:o:paloaltonetworks:pan-os:11.1.6:h10:*:*:*:*:*:*
paloaltonetworks pan-os 11.1.6 cpe:2.3:o:paloaltonetworks:pan-os:11.1.6:h14:*:*:*:*:*:*

References for CVE-2026-0300

cvelogic Threat Intelligence