Adminer Server-Side Request Forgery
CVE-2021-21311 is a high-severity server-side request forgery vulnerability in adminer from Vrana, with a CVSS 3.1 base score of 7.2 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected adminer versions: >= 4.0.0, < 4.7.9. The record does not name a fixed version, so check the vendor advisory. CISA added it to the Known Exploited Vulnerabilities catalogue on September 29, 2025, which means attacks have been observed in the wild.
Attackers are already exploiting this vulnerability, according to CISA.
What to do
- Check which version of adminer you run against the affected versions below, and install the vendor's latest release.
- CISA's 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.
- Read the advisory on github.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Vrana | adminer | >= 4.0.0, < 4.7.9 | Not stated |
| Debian | Debian Linux | 9.0 | Not stated |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- Confidentiality
- LowSome restricted data can be read.
- Integrity
- LowLimited modification of data is possible.
- Availability
- NoneAvailability is not affected.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 7.2 | High | CNA (github.com) |
| CVSS 3.1 | 7.2 | High | NVD |
| CVSS 2.0 | 6.4 | Medium | NVD |
Official description
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.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Server-Side Request Forgery
The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.
How developers prevent this class of flaw
- If there is a known list of applications, IP, hostname, and/or domains to which the product is allowed to communicate, then use allowlists to ensure that outgoing requests are restricted to these known entities. The allowlists could be in the application code or possibly enforced by firewalls or network segmentation.
- If the product is expected to be able to connect to arbitrary IP addresses or domains, consider using a denylist that includes private network addresses, internal domain names, etc. The denylist could be in the application code or possibly enforced by firewalls or network segmentation.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: active, automatable: yes, technical impact: partial).
- Added to CISA's Known Exploited Vulnerabilities catalogue.
- Deadline for US federal agencies to remediate, set by CISA.
- Record last changed materially (score, affected products, status or references).
References
Advisories
- github.com/vrana/adminer/security/advisories/GHSA-x5r2-hj5c-8jx6Third Party Advisory
Patches and release notes
Third-party and government advisories
- lists.debian.org/debian-lts-announce/2021/03/msg00002.htmlMailing List, Third Party Advisory
- packagist.org/packages/vrana/adminerProduct, Third Party Advisory
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-21311US Government Resource
Technical write-ups (may include proof of concept)
- github.com/vrana/adminer/files/5957311/Adminer.SSRF.pdfExploit, Third Party Advisory
Other vulnerabilities in adminer
- 7.2 High severity
- 8.6 High severity
- 9.8 Critical severity
- 7.2 High severity
- 8.8 High severity
- 8.1 High severity
Recent Server-Side Request Forgery vulnerabilities
- 9.8 Critical severity
- 7.5 High severity
- 5.5 Medium severity
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