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Full vulnerability report · 2026
CVE-2026-0300High confidence

Palo Alto Networks PAN-OS Out-of-bounds Write Vulnerability

Palo Alto Networks · PAN-OS

Official source article: Siemens SSA-967325 ↗. Check the applicable product and release in the original source.

9.3CriticalCVSS 4.0
Recommended action
Patch only the product branches with a verified fix

CISA confirms exploitation in the wild and lists 2026-05-09 as the remediation due date. Verified remediation exists for at least one product or source, but 1 structured product or package state remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Fix availability varies by product
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityCriticalOperational priority:Critical, unchanged from published severity.unchanged

Evidence used

  • CISA confirms exploitation in the wild.
  • The selected CVSS metric records a network-reachable, unauthenticated path with no user interaction.
  • EPSS is 41.71% for the current model date.

Compensating controls

  • Validate the affected product branch and deploy the verified fixed release.
  • Restrict the affected network interface to trusted sources where business-safe.
  • Increase monitoring for the attack path and post-exploitation behaviour described in the report.

Verification

  1. Confirm that the asset runs Palo Alto Networks PAN-OS and falls inside the recorded affected range.
  2. Verify the installed build against the product-specific fixed version after deployment.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: Within 3 daysRemediation target: Within 90 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Cross-source reconciliation

Remediation availability differs by product scope

Verified remediation exists for at least one product or source, but 1 structured product or package state remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Direct vendor intelligence

Authoritative vendor CSAF and VEX advisories

Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.

1 current
SSA-967325 · CSAF 2.0 · revision 4 · finalSiemens ProductCERTCVE-2026-0300
1 known affected

The vendor explicitly identifies these products as affected by this CVE.

  • RUGGEDCOM APE1808 with Palo Alto Networks Virtual NGFW with User-ID™ Authentication Portal configured and interface management profile with response pages enabled
Summary
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.
Remediation
Upgrade Palo Alto Networks Virtual NGFW V11.2.10-h6. Contact customer support to receive patch and update information
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2026-27879

CISA KEV mirrored by ENISA

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.

EUVD state
Present in the current official mapping
Known exploitation
Recorded by ENISA since 6 May 2026. Evidence sources: cisa_kev.
ENISA score
9.3 · CVSS 4.0
Advisory evidence
3 linked advisory records
Explicit mitigation evidence

Only statements that explicitly mention a fix, patch, update, workaround or mitigation are shown here.

  • csaf_ncscnl · NCSC-2026-0132Kwetsbaarheid verholpen in Palo Alto Networks PAN-OS
Recommended actionPatch only the product branches with a verified fix

CISA confirms exploitation in the wild and lists 2026-05-09 as the remediation due date. Verified remediation exists for at least one product or source, but 1 structured product or package state remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Fix availability varies by product
01

What, why and how

Palo Alto Networks PAN-OS contains an out-of-bounds write vulnerability in the User-ID Authentication Portal (aka Captive Portal) service that can allow an unauthenticated attacker to execute arbitrary code with root privileges on the PA-Series and VM-Series firewalls by sending specially crafted packets.

What

Palo Alto Networks PAN-OS contains an out-of-bounds write vulnerability in the User-ID Authentication Portal (aka Captive Portal) service that can allow an unauthenticated attacker to execute arbitrary code with root privileges on the PA-Series and VM-Series firewalls by sending specially crafted packets.

Why

A bounds error lets data be written beyond the intended memory region, potentially corrupting control data.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may execute code or commands in the affected security context.

What

Palo Alto Networks PAN-OS contains an out-of-bounds write vulnerability in the User-ID Authentication Portal (aka Captive Portal) service that can allow an unauthenticated attacker to execute arbitrary code with root privileges on the PA-Series and VM-Series firewalls by sending specially crafted packets.

Why

A bounds error lets data be written beyond the intended memory region, potentially corrupting control data.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may execute code or commands in the affected security context.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
Confirmed in the wild

CISA added this CVE to its Known Exploited Vulnerabilities catalogue on 2026-05-06.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path
a network path → Out-of-bounds Write → execute code or commands in the affected security context
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Not a CVSS 4.0 base metric
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-787 ↗

CWE-787: Out-of-bounds Write. The product writes data past the end, or before the beginning, of the intended buffer.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
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/AU:Y/R:U/V:C/RE:M/U:Red

Common Vulnerability Scoring System 4.0: the compact vector below is decoded into plain language.

AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.ATNoneAttack requirements: No additional deployment or execution condition is required.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.VCHighVulnerable-system confidentiality: A successful attack can cause a major loss.VIHighVulnerable-system integrity: A successful attack can cause a major loss.VAHighVulnerable-system availability: A successful attack can cause a major loss.SCLowSubsequent-system confidentiality: A successful attack can cause a limited loss.SILowSubsequent-system integrity: A successful attack can cause a limited loss.SANoneSubsequent-system availability: No direct loss is represented by this metric.
Post-exploitation / living off the land
After compromise, an attacker may use built-in shells, scripting engines, scheduled tasks and native network utilities for discovery, persistence or movement. This is a plausible LoTL path, not evidence that it has occurred for every attack.
NetworkUnauthenticatedRemote code executionCWE-787CISA KEV
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

ENISA EUVD · EUVD-2026-27879Known-exploited evidence recorded

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.

Official EUVD record ↗
BSI · German · WID-SEC-2026-1366Palo Alto Networks PAN-OS: Schwachstelle ermöglicht Ausführen von beliebigem Programmcode mit Administratorrechten

Ein entfernter, anonymer Angreifer kann eine Schwachstelle in Palo Alto Networks PAN-OS ausnutzen, um beliebigen Programmcode mit Administratorrechten auszuführen.

Official advisory ↗
Canadian Centre for Cyber Security · English · AV26-425Palo Alto Networks security advisory (AV26-425) – Update 1

On May 5, 2026, Palo Alto Networks published a security advisory to address critical vulnerabilities in the following products: Palo Alto has received reports that CVE-2026-0300 is being actively exploited.

Official advisory ↗
Cyber Security Agency of Singapore · English · CSA-SB-20260513Security Bulletin 13 May 2026

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 13 May 2026, published on 13 May 2026. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
CISA · English · ICSA-26-139-02Siemens RUGGEDCOM APE1808 Devices

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.

Official advisory ↗
CERT-FR · French · CERTFR-2026-AVI-0537Vulnérabilité dans Palo Alto Networks User-ID Authentication Portal

Une vulnérabilité a été découverte dans Palo Alto Networks User-ID Authentication Portal. Elle permet à un attaquant de provoquer une exécution de code arbitraire à distance. Palo Alto Networks indique que la vulnérabilité CVE-2026-0300 est activement exploitée. L'éditeur indique que les correctifs seront publiés le 13 et le 28 mai 2026.

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2026-014858Palo Alto NetworksのPAN-OSにおける境界外書き込みに関する脆弱性

Palo Alto NetworksのPAN-OSソフトウェアにおけるUser-ID認証ポータル（別名Captive Portal）サービスにバッファオーバーフローの脆弱性があります。この脆弱性により、認証されていない攻撃者が特別に細工されたパケットを送信すると、PA-SeriesおよびVM-Seriesファイアウォール上でroot権限の任意のコードを実行できる可能性があります。この問題のリスクは、ベストプラクティスガイドラインhttps://knowledgebase.paloaltonetworks.com/KCSArticleDetailに従い、User-ID認証ポータルへのアクセスを信頼できる内部IPアドレスのみに制限することで大幅に低減されます。Prisma Access、Cloud NGFW、およびPanoramaアプライアンスはこの脆弱性の影響を受けません。

Official advisory ↗
KISA KrCERT/CC · Korean · KNVD-6780Palo Alto Networks 제품 보안 업데이트 권고

PAN-OS에서 발생하는 Out-of-bounds Write 취약점(CVE-2026-0300) [1][2]

Official advisory ↗
KISA KrCERT/CC · Korean · KNVD-6778美 CISA 발표 주요 Exploit 정보공유(Update. 2026-05-06)

Palo Alto Networks PAN-OS Out-of-bounds Write Vulnerability

Official advisory ↗
NCSC-NL · Dutch · NCSC-2026-0132Kwetsbaarheid verholpen in Palo Alto Networks PAN-OS

A buffer overflow vulnerability in Palo Alto Networks PAN-OS User-ID Authentication Portal allows unauthenticated attackers to execute arbitrary code with root privileges on PA-Series and VM-Series firewalls, excluding Prisma Access, Cloud NGFW, and Panorama appliances.

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Fix availability varies by product
Affected
RUGGEDCOM APE1808 with Palo Alto Networks Virtual NGFW with User-ID™ Authentication Portal configured and interface management profile with response pages enabled
Fixed
Action
Use the product-specific evidence above. Patch only products with a verified fixed release, and keep every affected or under-investigation state without a matching fix in the remediation queue.
Workaround
A mitigation or workaround reference is available from the source linked below; validate it against the affected product and version.
04

Evidence and provenance

Published 6 May 2026 · Last source change 15 Oct 2026, 01:11 UTC · CWE-787 · Out-of-bounds Write

CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2026-27879
Product sourceVendor CSAF · Siemens ProductCERT
Remediation sourceVendor CSAF · Siemens ProductCERT
CWE sourceCNA
NVD statusNVD enriched

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates ↗
  1. BlackTree coverageBlackTree article coverage changed from no BlackTree article to 1 BlackTree article.
    Before
    no BlackTree article
    After
    1 BlackTree article
    BlackTree editorial ↗
  2. Affected versionsThe structured affected or fixed version information changed.
    Before
    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 · Fixed: All
    After
    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 · Fixed: Cloud NGFW: All; Prisma Access: All
    CNA ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Added to CISA KEV
Fixed release or patch reference recorded
ENISA EUVD · EUVD-2026-27879↗Vendor CSAF · Siemens ProductCERT · Siemens SSA-967325↗CISA KEV record↗CVE authority or vendor reference↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2026-0300 · cve.blacktree.nl