CVE-2023-53979: MyBB 1.8.32 contains a chained vulnerability that allows authenticated administrators to bypass avatar upload

This month

HIGH 8.8DOWNGRADE

CVE-2023-53979 is a high-severity flaw (CVSS 8.8) affecting mybb. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

MyBB 1.8.32 contains a chained vulnerability that allows authenticated administrators to bypass avatar upload restrictions and execute arbitrary code. Attackers can modify upload path settings, upload a malicious PHP-embedded image file, and execute commands through the language configuration editing interface.

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	0.8% (top 43%)
CISA exploited list	No
Weakness	CWE-22
Published	2025-12-22
Last modified	2026-06-17

Publisher (CNA): VulnCheck · Vendor: mybb

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

Am I affected?

Timeline

2025-12-22 22:16 UTCPublished CVE record published
2026-06-17 06:46 UTCUpdated Record last modified

mybb mybb DOWNGRADE

Affected: 1.8.32

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.8.32

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 1.8.32 (Debian / Ubuntu)

apt-cache madison mybb sudo apt install mybb=<VERSION_BEFORE_1.8.32> sudo apt-mark hold mybb

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

dnf --showduplicates list mybb sudo dnf downgrade mybb-<VERSION_BEFORE_1.8.32> sudo dnf versionlock add mybb

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-2023-53979?

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

Is CVE-2023-53979 being exploited?

CVE-2023-53979 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-2023-53979 affect?

CVE-2023-53979 affects mybb. Severity is high (CVSS 8.8). MyBB 1.8.32 contains a chained vulnerability that allows authenticated administrators to bypass avatar upload restrictions and execute arbitrary code. Attackers can modify upload path settings, upload a malicious PHP-embedded image file, an

How urgent is CVE-2023-53979?

Priority 50/100. High severity; Public exploit reference

Software pages

PHP vulnerabilities

Related CVEs

CVE-2025-48941 MEDIUM 5.3 UPGRADE MyBB is free and open source forum software
CVE-2025-48940 HIGH 7.2 UPGRADE MyBB is free and open source forum software
CVE-2025-29460 HIGH 7.6 DOWNGRADE An issue in MyBB 1.8.38 allows a remote attacker to obtain sensitive information via the Add Mycode function
CVE-2025-29459 HIGH 7.6 DOWNGRADE An issue in MyBB 1.8.38 allows a remote attacker to obtain sensitive information via the Mail function
CVE-2025-29458 HIGH 7.6 DOWNGRADE An issue in MyBB 1.8.38 allows a remote attacker to obtain sensitive information via the Change Avatar functio

References

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