CVE-2021-27889
MEDIUMCVSS 6.1/10EPSS 5.07%
Last modified
CVE-2021-27889 is a medium-severity vulnerability rated 6.1/10 on the CVSS scale. Cross-site Scripting (XSS) vulnerability in MyBB before 1.8.26 via Nested Auto URL when parsing messages.. EPSS estimates a 5.07% chance of exploitation in the next 30 days.
Description
Cross-site Scripting (XSS) vulnerability in MyBB before 1.8.26 via Nested Auto URL when parsing messages.
Metrics
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Weakness Enumeration
Affected Software
| Vendor | Product | Versions |
|---|---|---|
| Mybb | Mybb | < 1.8.26 |
References
- http://packetstormsecurity.com/files/161908/MyBB-1.8.25-Remote-Command-Execution.htmlExploit, Third Party Advisory, VDB Entry
- https://blog.sonarsource.com/mybb-remote-code-execution-chainExploit, Third Party Advisory
- https://github.com/mybb/mybb/security/advisories/GHSA-xhj7-3349-mqcmPatch, Third Party Advisory
- http://packetstormsecurity.com/files/161908/MyBB-1.8.25-Remote-Command-Execution.htmlExploit, Third Party Advisory, VDB Entry
- https://blog.sonarsource.com/mybb-remote-code-execution-chainExploit, Third Party Advisory
- https://github.com/mybb/mybb/security/advisories/GHSA-xhj7-3349-mqcmPatch, Third Party Advisory
Timeline
- Published
- Last Modified
- Status
- Modified
Frequently Asked Questions
What is CVE-2021-27889?
Cross-site Scripting (XSS) vulnerability in MyBB before 1.8.26 via Nested Auto URL when parsing messages.
How severe is CVE-2021-27889?
CVE-2021-27889 has a CVSS score of 6.1/10 (MEDIUM severity). The EPSS model estimates a 5.07% probability of exploitation in the next 30 days.
How do I fix CVE-2021-27889?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.
How Strix Helps
- How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
- Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
- PR ReviewsPentest every pull request so vulnerable code is caught before it ships to production.
- AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.
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Are you affected by CVE-2021-27889?
Run a free Strix scan to check your systems for this vulnerability.
Scan your code nowSource: NVD / NIST