CVE-2021-21311 Adminer Adminer: web page flaw
In plain words: A web app can be made to act on someone's behalf or reach places it should not. Stolen sessions, actions taken as the victim, or access to internal systems.
Confirmed exploited by CISA on · US federal patch deadline Oct 20, 2025
What to do
- Install Adminer's security update for Adminer. If no update exists, follow the vendor's workaround or stop using the product until one ships.
- Keep a list of every internet-facing server you run so nothing is forgotten.
- Patch anything in this catalog first, ahead of normal patch cycles.
- Put admin and file-transfer apps behind a VPN or single sign-on instead of the open internet.
Who is affected
Work IT. Aimed mostly at company systems — you are affected through the companies you use, not your own phone.
What's at risk: Mass data theft and ransomware: a single flaw in a file-transfer or email server has exposed thousands of organisations at once.
The details
- Official name
- Adminer Server-Side Request Forgery Vulnerability
- Product
- Adminer Adminer
- CISA description
- Adminer contains a server-side request forgery vulnerability that, when exploited, allows a remote attacker to obtain potentially sensitive information.
- Type of flaw
- Web page flaw (CWE-918)
- Confirmed exploited
- Sep 29, 2025
- US federal patch deadline
- Oct 20, 2025
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Answering about CVE-2021-21311 ·
Questions about CVE-2021-21311
Is CVE-2021-21311 being exploited?
Yes. CISA added CVE-2021-21311 to its Known Exploited Vulnerabilities catalog on Sep 29, 2025, which means there is reliable evidence of real-world attacks.
How do I fix CVE-2021-21311?
Install Adminer's security update for Adminer. If no update exists, follow the vendor's workaround or stop using the product until one ships. Keep a list of every internet-facing server you run so nothing is forgotten.
Am I affected by CVE-2021-21311?
Only if you use Adminer Adminer. Aimed mostly at company systems — you are affected through the companies you use, not your own phone.