How severe is CVE-2021-21311?

CVE-2021-21311 has a CVSS score of 7.2/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2021-21311?

CVE-2021-21311 affects the following packages: vrana/adminer (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2021-21311?

Update vrana/adminer to 4.7.9 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-21311 is resolved across your whole dependency graph.

How do I detect CVE-2021-21311 in my Packagist dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for vrana/adminer, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2021-21311 if there is no patch (or I can't update yet)?

Restrict outbound requests from the affected component to an allowlist of hosts, block access to link-local and internal address ranges at the network layer, and require authentication on internal services so a forged request cannot reach them unauthenticated.

Is CVE-2021-21311 actively exploited in the wild?

Yes. There are 4 known exploit references for CVE-2021-21311, including 2 in-the-wild exploitations observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2021-21311?

CVE-2021-21311 has an EPSS (Exploit Prediction Scoring System) score of 98.5%, placing it in the 100th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. A score above 50% indicates significantly elevated exploitation risk — immediate patching is strongly recommended.

Is CVE-2021-21311 in the CISA Known Exploited Vulnerabilities catalog?

Yes. CVE-2021-21311 (Adminer Server-Side Request Forgery Vulnerability) was added to CISA's Known Exploited Vulnerabilities (KEV) catalog on 2025-09-29. CISA required all US federal civilian agencies to remediate this vulnerability by 2025-10-20. The required action was: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. Being listed in the KEV catalog is the strongest possible confirmation of active exploitation — treat this as a critical priority.

What type of vulnerability is CVE-2021-21311?

CVE-2021-21311 is classified as Server-Side Request Forgery (SSRF) (CWE-918). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

Is there exploit tooling available for CVE-2021-21311?

A Nuclei detection template exists for CVE-2021-21311, meaning automated scanners can fingerprint it. Public exploit tooling significantly increases real-world risk — prioritize patching and ensure detection coverage. Exploit tooling should only ever be used in isolated, authorized testing environments.

When was CVE-2021-21311 published, and has it been updated?

CVE-2021-21311 was published on February 11, 2021 and was last updated on October 20, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐘

🐘 Packagist

CISA KEV · ACTIVELY EXPLOITED

HIGH severity

CVE-2021-21311 — adminer

HIGHFix: vrana/adminer@ccd2374

CVE-2021-21311 is a high-severity (CVSS 7.2) Server-Side Request Forgery (SSRF) vulnerability in vrana/adminer. It is in CISA's Known Exploited Vulnerabilities catalog (added 2025-09-29) — treat it as actively exploited and patch now. A fix is available for vrana/adminer — see the affected versions and patch details below.

SSRF in adminer

Also known asGHSA-x5r2-hj5c-8jx6

Published

Feb 11, 2021

Updated

Oct 20, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

4 known

Exploitation data as of Oct 23, 2026 · OSV.dev, NVD, CISA KEV, FIRST.org (EPSS)

Exploitation Status

Actively exploited in the wild

Confirmed by CISA's Known Exploited Vulnerabilities catalog on 2025-09-29. Federal agencies were required to remediate by 2025-10-20.
CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.

Exploitation and automatability from CISA (KEV catalog and SSVC triage) for CVE-2021-21311.

EPSS Exploitation Probability

via FIRST.org ↗

98.5%probability of exploitation in next 30 days

Very High Risk0.00%

Lower risk than most CVEs100th percentile — riskier than 100% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2021-21311 by exploitation likelihood (EPSS) against impact (CVSS). In the shaded patch-first corner (EPSS 50%+, CVSS 7.0+).

Where this sits among everything scored

Of 395,249 CVEs with a current EPSS score, this one falls in the ≥ 90% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected

🐘vrana/adminer

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.

Description

Impact

Users of Adminer versions bundling all drivers (e.g. adminer.php) are affected.

Patches

Patched by ccd2374b, included in version 4.7.9.

Workarounds

Use a single driver version (e.g. adminer-mysql.php).
Protect access to Adminer also by other means, e.g. by HTTP password, IP address limiting or by OTP plugin.

References

https://github.com/vrana/adminer/files/5957311/Adminer.SSRF.pdf

For more information

If you have any questions or comments about this advisory:

Comment at ccd2374b.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`vrana/adminer`	all versions	4.7.9`composer require vrana/adminer:^4.7.9`

Affected Products

2 products · 2 configurations

Application

admineradminer

≥ 4.0.0 && < 4.7.9

range

debian linuxdebian

1 version

9.0

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

Adminer is an open-source database management in a single PHP file. In a…

github.comNVDJun 2021

Adminer is an open-source database management in a single PHP file. In a…

github.comGithubFeb 2022

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for vrana/adminer, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update vrana/adminer to 4.7.9 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-21311 is resolved across your whole dependency graph.
Workarounds
Restrict outbound requests from the affected component to an allowlist of hosts, block access to link-local and internal address ranges at the network layer, and require authentication on internal services so a forged request cannot reach them unauthenticated.

How to detect CVE-2021-21311

A community-maintained Nuclei template exists for this CVE. You can scan for it directly:

nuclei -id cve-2021-21311 -u https://target

Template: Adminer <4.7.9 - Server-Side Request Forgery
Severity: high
Impact: Successful exploitation of this vulnerability could lead to unauthorized access to internal resources and potential data leakage.
Remediation: Upgrade to version 4.7.9 or later.

Template by ProjectDiscovery nuclei-templates (Adam Crosser, pwnhxl), MIT licensed. View the full template. Scan only systems you are authorised to test.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

UbuntuHIGH

USN-5271-1Ubuntu

Frequently Asked Questions

### Impact Users of Adminer versions bundling all drivers (e.g. `adminer.php`) are affected. ### Patches Patched by ccd2374b, included in version [4.7.9](https://github.com/vrana/adminer/releases/tag/v4.7.9). ### Workarounds * Use a single driver version (e.g. `adminer-mysql.php`). * Protect access to Adminer also by other means, e.g. by HTTP password, IP address limiting or by OTP [plugin](https://www.adminer.org/plugins/). ### References https://github.com/vrana/adminer/files/5957311/Adminer.SSRF.pdf ### For more information If you have any questions or comments about this advisory: * Co