CVE-2021-27279 json
MyBB before 1.8.25 allows stored XSS via nested [email] tags with MyCode (aka BBCode).
published 2021-02-22 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-14044
- cvss
- 5.4
- version 3.1, NVD
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 1.0%
- EPSS 1.0% chance of exploitation in 30 days, percentile 61%
- public exploits
- 0
- none known
Summary
MyBB before 1.8.25 allows stored XSS via nested [email] tags with MyCode (aka BBCode).
Patch / fix
Exploit prediction
0.96% chance of exploitation in the next 30 days, higher than 61% of all scored CVEs (FIRST EPSS, 2026-11-08).
Exploits and checks
- github.com https://github.com/mybb/mybb/security/advisories/GHSA-6483-hcpp-p75w referenced PoC, tagged "exploit" by a source, unverified
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| NVD | 3.1 | 5.4 | CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N |
| NVD | 2.0 | 3.5 | AV:N/AC:M/Au:S/C:N/I:P/A:N |
Classification
- Weakness
-
- CWE-79 Improper Neutralization of Input During Web Page Generation
References
-
github.com
/mybb/mybb/commit/cb781b49116bf5c4d8deca3e17498122b701677a
patch, third-party-advisory
-
github.com
/mybb/mybb/security/advisories/GHSA-6483-hcpp-p75w
exploit, third-party-advisory
-
mybb.com
/versions/1.8.25/
release-notes, vendor-advisory
Sources
- CVE List CVE-2021-27279
- NVD CVE-2021-27279
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.