CVE-2021-27889
Cross-site Scripting (XSS) vulnerability in MyBB before 1.8.26 via Nested Auto URL when parsing messages.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- Required
What an attacker can affect
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
Exploit likelihood
What each source reports
NVD Score used
Cross-site Scripting (XSS) vulnerability in MyBB before 1.8.26 via Nested Auto URL when parsing messages.
- Record
CVE-2021-27889- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - CVSS 2.0
- 4.3 Medium
AV:N/AC:M/Au:N/C:N/I:P/A:N - Weakness
- CWE-79
- Updated
- 2026-11-02
CVE List No score
Cross-site Scripting (XSS) vulnerability in MyBB before 1.8.26 via Nested Auto URL when parsing messages.
- Record
CVE-2021-27889- Updated
- 2026-11-02
EUVDEUVD-2021-14626 No score
Cross-site Scripting (XSS) vulnerability in MyBB before 1.8.26 via Nested Auto URL when parsing messages.
- Record
EUVD-2021-14626- Updated
- 2026-11-03
Affected products
Public exploits
Links only. Every CVE stores no exploit code.
| Source | Link | Date |
|---|---|---|
| Exploit-DB | MyBB 1.8.25 - Chained Remote Command Execution | 2021-03-22 |
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE List, Exploit-DB, NVD |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-27889 is a medium vulnerability (CVSS 6.1) in Mybb, published March 15, 2021. Public exploit code exists. EPSS puts the chance of exploitation in the next 30 days at 5.07%, the 92nd percentile. No source names a fixed version.