What’s Vulnerable › Vulnerabilities

CVE-2021-27279

• Severity: medium (CVSS 5.4 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.0% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2021-02-22 · updated 2026-06-17
• Weakness: CWE-79

Description

MyBB before 1.8.25 allows stored XSS via nested [email] tags with MyCode (aka BBCode).

Affected products

• mybb: before 1.8.25 — fixed in 1.8.25

How to fix

Upgrade to a fixed version: mybb 1.8.25. Check the vendor advisory for mitigations.

References

• https://github.com/mybb/mybb/commit/cb781b49116bf5c4d8deca3e17498122b701677a
• https://github.com/mybb/mybb/security/advisories/GHSA-6483-hcpp-p75w
• https://mybb.com/versions/1.8.25/
• https://github.com/mybb/mybb/commit/cb781b49116bf5c4d8deca3e17498122b701677a
• https://github.com/mybb/mybb/security/advisories/GHSA-6483-hcpp-p75w
• https://mybb.com/versions/1.8.25/

Get alerted when CVE-2021-27279 or the next vulnerability affects your stack