CVE-2019-13956: Discuz!ML 3.2 through 3.4 allows remote attackers to execute arbitrary PHP code via a modified language cookie

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CRITICAL 9.8REMOTEUPGRADE

CVE-2019-13956 is a critical-severity flaw (CVSS 9.8) affecting discuz\!ml. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Discuz!ML 3.2 through 3.4 allows remote attackers to execute arbitrary PHP code via a modified language cookie, as demonstrated by changing 4gH4_0df5_language=en to 4gH4_0df5_language=en'.phpinfo().'; (if the random prefix 4gH4_0df5_ were used).

Why this priority

Critical severity
EPSS top 8%: very likely to be exploited
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	4.6% (top 8%)
CISA exploited list	No
Weakness	CWE-94
Published	2019-07-18
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: codersclub

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

Am I affected?

Timeline

2019-07-18 18:15 UTCPublished CVE record published
2026-06-17 02:17 UTCUpdated Record last modified

codersclub discuz\!ml UPGRADE

Affected: >= 3.2 and <= 3.4

Fixed in: newer than 3.4

Safe to downgrade to: a release before 3.2

1. Check installed version

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

2. UPGRADE to newer than 3.4 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade discuzml

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade discuzml

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 3.2 (Debian / Ubuntu)

apt-cache madison discuzml sudo apt install discuzml=<VERSION_BEFORE_3.2> sudo apt-mark hold discuzml

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list discuzml sudo dnf downgrade discuzml-<VERSION_BEFORE_3.2> sudo dnf versionlock add discuzml

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-2019-13956?

discuz\!ml: upgrade to newer than 3.4. Exact commands for each OS are on this page.

Is CVE-2019-13956 being exploited?

CVE-2019-13956 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-2019-13956 affect?

CVE-2019-13956 affects discuz\!ml. Severity is critical (CVSS 9.8). Discuz!ML 3.2 through 3.4 allows remote attackers to execute arbitrary PHP code via a modified language cookie, as demonstrated by changing 4gH4_0df5_language=en to 4gH4_0df5_language=en'.phpinfo().'; (if the random prefix 4gH4_0df5_ were u

How urgent is CVE-2019-13956?

Priority 67/100. Critical severity; EPSS top 8%: very likely to be exploited; Public exploit reference; Remotely exploitable, no login, no user action

Software pages

PHP vulnerabilities

References

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