CVE-2023-53933: Serendipity 2.4.0 contains a remote code execution vulnerability that allows authenticated attackers to upload

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HIGH 8.8DOWNGRADE

CVE-2023-53933 is a high-severity flaw (CVSS 8.8) affecting serendipity. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Serendipity 2.4.0 contains a remote code execution vulnerability that allows authenticated attackers to upload malicious PHP files with .phar extension. Attackers can upload files with system command payloads to the media upload endpoint and execute arbitrary commands on the server.

Why this priority

High severity
Public exploit reference

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

Risk facts

CVSS score	8.8 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	1.0% (top 37%)
CISA exploited list	No
Weakness	CWE-434
Published	2025-12-17
Last modified	2026-06-17

Publisher (CNA): VulnCheck · Vendor: s9y

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

Am I affected?

Timeline

2025-12-17 23:15 UTCPublished CVE record published
2026-06-17 06:46 UTCUpdated Record last modified

s9y serendipity DOWNGRADE

Affected: 2.4.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.4.0

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 2.4.0 (Debian / Ubuntu)

apt-cache madison serendipity sudo apt install serendipity=<VERSION_BEFORE_2.4.0> sudo apt-mark hold serendipity

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

dnf --showduplicates list serendipity sudo dnf downgrade serendipity-<VERSION_BEFORE_2.4.0> sudo dnf versionlock add serendipity

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-2023-53933?

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

Is CVE-2023-53933 being exploited?

CVE-2023-53933 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-2023-53933 affect?

CVE-2023-53933 affects serendipity. Severity is high (CVSS 8.8). Serendipity 2.4.0 contains a remote code execution vulnerability that allows authenticated attackers to upload malicious PHP files with .phar extension. Attackers can upload files with system command payloads to the media upload endpoint an

How urgent is CVE-2023-53933?

Priority 52/100. High severity; Public exploit reference

Software pages

PHP vulnerabilities

Related CVEs

CVE-2026-39971 HIGH 7.2 UPGRADE Serendipity is a PHP-powered weblog engine
CVE-2026-39963 MEDIUM 6.9 UPGRADE Serendipity is a PHP-powered weblog engine
CVE-2024-58282 HIGH 7.2 DOWNGRADE Serendipity 2.5.0 contains a remote code execution vulnerability that allows authenticated administrators to u
CVE-2023-53932 MEDIUM 5.4 DOWNGRADE Serendipity 2.4.0 contains a stored cross-site scripting vulnerability that allows authenticated users to inje
CVE-2023-31576 HIGH 8.8 DOWNGRADE An arbitrary file upload vulnerability in Serendipity 2.4-beta1 allows attackers to execute arbitrary code via

References

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