XSS in Mybb
CVE-2021-27889
Cross-site Scripting (XSS) vulnerability in MyBB before 1.8.26 via Nested Auto URL when parsing messages.
Vulnerability class: XSS (Cross-Site Scripting)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.
EPSS exploit prediction
EPSS: 0.051 (92.0th percentile), scored .
Low probability of exploitation in the next 30 days, but still tracked. 92nd percentile — 92.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.051 · newest: 0.051 · change: 0.000
Affected products
Weakness classification (CWE)
Public proof-of-concept exploits
References
- github.com/mybb/mybb/security/advisories/GHSA-xhj7-3349-mqcm (Patch, Third Party Advisory)
- packetstormsecurity.com/files/161908/MyBB-1.8.25-Remote-Command-Execution.html (Exploit, VDB Entry, Third Party Advisory)
- blog.sonarsource.com/mybb-remote-code-execution-chain (Exploit, Third Party Advisory)
Frequently asked questions
- What is CVE-2021-27889?
- CVE-2021-27889 is a medium-severity vulnerability in Mybb, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2021-03-15.
- How severe is CVE-2021-27889?
- Medium severity. CVSS v3 base score is 6.1 out of 10.
- Is CVE-2021-27889 known to be exploited?
- 5 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.