CVE-2016-9866: An issue was discovered in phpMyAdmin

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CRITICAL 9.8REMOTEDOWNGRADE

CVE-2016-9866 is a critical-severity flaw (CVSS 9.8) affecting phpmyadmin. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An issue was discovered in phpMyAdmin. When the arg_separator is different from its default & value, the CSRF token was not properly stripped from the return URL of the preference import action. All 4.6.x versions (prior to 4.6.5), 4.4.x versions (prior to 4.4.15.9), and 4.0.x versions (prior to 4.0.10.18) are affected.

Why this priority

Critical severity
Remotely exploitable, no login, no user action

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.0% (top 36%)
CISA exploited list	No
Weakness	CWE-352
Published	2016-12-11
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: phpmyadmin

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2016-12-11 03:00 UTCPublished CVE record published
2026-06-17 00:56 UTCUpdated Record last modified

phpmyadmin phpmyadmin DOWNGRADE

Affected: 4.6.0 · 4.6.1 · 4.6.2 · 4.6.3 · 4.6.4 · 4.4.0 · 4.4.1 · 4.4.1.1

Fixed in: no fixed release known

Safe to downgrade to: a release before 4.0.0

1. Check installed version

apt-cache policy phpmyadmin || rpm -q phpmyadmin || phpmyadmin --version

2. No fixed release: DOWNGRADE to a release before 4.0.0 (Debian / Ubuntu)

apt-cache madison phpmyadmin sudo apt install phpmyadmin=<VERSION_BEFORE_4.0.0> sudo apt-mark hold phpmyadmin

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list phpmyadmin sudo dnf downgrade phpmyadmin-<VERSION_BEFORE_4.0.0> sudo dnf versionlock add phpmyadmin

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2016-9866?

phpmyadmin: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2016-9866 being exploited?

CVE-2016-9866 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2016-9866 affect?

CVE-2016-9866 affects phpmyadmin. Severity is critical (CVSS 9.8). An issue was discovered in phpMyAdmin. When the arg_separator is different from its default & value, the CSRF token was not properly stripped from the return URL of the preference import action. All 4.6.x versions (prior to 4.6.5), 4.4.x ve

How urgent is CVE-2016-9866?

Priority 55/100. Critical severity; Remotely exploitable, no login, no user action

Software pages

phpMyAdmin vulnerabilities

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References

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