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CVE-2021-27889

MediumPublished

Cross-site Scripting (XSS) vulnerability in MyBB before 1.8.26 via Nested Auto URL when parsing messages.

Published: Mar 15, 2021
Updated: Aug 3, 2024
Assigning CNA: mitre
Evidence observed: Mar 22, 2021

Primary CVSS

6.1/ 10Medium

nvd · CVSS 3.1

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

EPSS probability estimate

5.1%

Low · next 30 days

Percentile: 92.0%
Model date: Sep 21, 2026

EPSS is a statistical estimate, not a certainty or a measure of impact. Combine it with CVSS, KEV status, exposure and your environment.

Summary

Cross-site Scripting (XSS) vulnerability in MyBB before 1.8.26 via Nested Auto URL when parsing messages.

Sources

Mybb-XSS_SQL_RCE-POCPoC
Mybb associate CVE-2021-27890 & CVE-2021-27889 to RCE poc
MyBB 1.8.25 - Chained Remote Command ExecutionExploit
SivertPL · php · Mar 22, 2021

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