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

> Unauthenticated attackers can execute arbitrary code with root privileges on PAN-OS firewalls via a buffer overflow in the User-ID Authentication Portal.

- **Severity:** Critical 9.3 (`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`)
- **Exploited in the wild:** Yes, since 6 May 2026 (CISA KEV)
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 6 May 2026
- **Updated:** 15 Oct 2026
- **Also known as:** GHSA-3vfh-3cpw-2378

## What is CVE-2026-0300?

CVE-2026-0300 is a critical memory corruption vulnerability in Paloaltonetworks Pan-Os, published on 6 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2026-0300?

It affects 2 products.


Products: Paloaltonetworks Pan-Os, Siemens Ruggedcom Ape1808 Firmware.

## How do I fix CVE-2026-0300?

No fix has been published for CVE-2026-0300 yet. Limit exposure of the affected software until one is available. US federal agencies must fix it by 9 May 2026.

## Is CVE-2026-0300 being exploited?

Yes. Attackers have exploited CVE-2026-0300 in the wild since at least 6 May 2026.

Public exploit code:

- https://github.com/p3Nt3st3r-sTAr/CVE-2026-0300-POC (github_poc): https://github.com/p3Nt3st3r-sTAr/CVE-2026-0300-POC
- Security Research and Proof-of-Concept (PoC) for CVE-2026-0300 : Unauthenticated Remote Code Execution (RCE) in Palo Alto Networks PAN-OS User-ID Portal. (github_poc): https://github.com/matad0r-maghribi/CVE-2026-0300-PANOS
- A research-grade Proof-of-Concept (PoC) for CVE-2026-0300, targeting the Buffer Overflow vulnerability in Palo Alto Networks PAN-OS User-ID™ Authentication Portal (CWE-787). (github_poc): https://github.com/qassam-315/PAN-OS-User-ID-Buffer-Overflow-PoC
- Scanner: CVE-2026-0300 PAN-OS User-ID Captive Portal Buffer Overflow RCE — Python CLI for detecting actively exploited BOF vulnerability in Palo Alto firewalls (CISA KEV 2026-05-13) (github_poc): https://github.com/ridhinva/panos-captive-portal-rce
- a honeypot for CVE-2026-0300 (github_poc): https://github.com/mr-r3b00t/CVE-2026-0300
- CVE-2026-0300 (github_poc): https://github.com/0xredash/CVE-2026-0300

## Other vulnerabilities in Paloaltonetworks Pan-Os

- [CVE-2024-3400](https://insights.sbomify.com/CVE-2024-3400/): Palo Alto Networks PAN-OS Command Injection (critical 10.0, exploited in the wild)
- [CVE-2020-2021](https://insights.sbomify.com/CVE-2020-2021/): Palo Alto Networks PAN-OS Authentication Bypass (critical 10.0, exploited in the wild)
- [CVE-2017-15944](https://insights.sbomify.com/CVE-2017-15944/): Palo Alto Networks PAN-OS Remote Code Execution (critical 9.8, exploited in the wild)
- [CVE-2024-0012](https://insights.sbomify.com/CVE-2024-0012/): Palo Alto Networks PAN-OS Management Interface Authentication Bypass (critical 9.3, exploited in the wild)
- [CVE-2026-109618](https://insights.sbomify.com/CVE-2026-109618/): PHP Memory Corruption (critical 9.2, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-0300 and fix it if it is affected.

What it is: CVE-2026-0300 is a critical memory corruption vulnerability in Paloaltonetworks Pan-Os, published on 6 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: Yes. Attackers have exploited CVE-2026-0300 in the wild since at least 6 May 2026.

Affected product: Paloaltonetworks Pan-Os. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-0300/ (Markdown: https://insights.sbomify.com/CVE-2026-0300/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-0300
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-0300
- OSV: https://osv.dev/vulnerability/CVE-2026-0300

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-0300/
Summaries are generated and may contain mistakes; the official description above is the record.