CVE-2021-21311: Adminer Server-Side Request Forgery Vulnerability

Should you act?

Exploited: patch now if you run it

CISA has confirmed exploitation in the wild. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• Yes, if you run Adminer Adminer. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2025-09-29, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2025-10-20; treat that as the outer limit, not the target.
• EPSS 98.5%, percentile 99.9: FIRST’s model estimates a 98.5% chance of exploitation activity in the next 30 days, higher than 99.9% of all scored CVEs (very high). EPSS is a probability, not a verdict.
• Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.

What it is

Adminer is an open-source database management in a single PHP file. In adminer from version 4.0.0 and before 4.7.9 there is a server-side request forgery vulnerability. Users of Adminer versions bundling all drivers (e.g. adminer.php) are affected. This is fixed in version 4.7.9.

CISA’s summary

Adminer contains a server-side request forgery vulnerability that, when exploited, allows a remote attacker to obtain potentially sensitive information.

Weakness type: CWE-918.

Product: Adminer Adminer · Assigned by: GitHub_M · Published: 2021-02-11

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: none (no login)
• User interaction: none
• Scope: changed (can affect other components)

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: added 2025-09-29; federal due date 2025-10-20. Known ransomware use: Unknown.
• CISA 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.
• CISA SSVC assessment: exploitation active, automatable yes, technical impact partial.
• FIRST EPSS (model of 2026-10-21): 98.46% probability of exploitation activity in the next 30 days; percentile 99.9.

Timeline

• 2021-02-11 — CVE record published by GitHub_M
• 2025-09-29 — Added to CISA’s Known Exploited Vulnerabilities catalog
• 2025-10-20 — CISA remediation deadline for US federal agencies
• 2025-10-21 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vendor and project advisories, patches

1. Listed in CISA KEV notes (github.com) github.com

Vulnerability records

1. CVE.org record CVE-2021-21311 cve.org
2. NVD entry CVE-2021-21311 nvd.nist.gov

Government

1. CISA Known Exploited Vulnerabilities catalog entry cisa.gov

Other references from the CVE record and advisory

1. github.com github.com
2. packagist.org packagist.org
3. github.com github.com
4. [debian-lts-announce] 20210302 [SECURITY] [DLA 2580-1] adminer security update lists.debian.org

All exploited Adminer vulnerabilities · Today’s Security Digest