CVE-2021-27889

Mybb vulnerability

CVSS

6.1

EPSS

5.1%

EPSS pct

91th

Exploited

No known

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

Affected vendor

Mybb

Affected product

Mybb

CVSS vector

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

Weakness type (CWE)

CWE-79 — Cross-Site Scripting (XSS)

Published

2021-03-15

Risk analysis

Based on its CVSS vector, this vulnerability is exploitable over the network, low attack complexity, requiring no privileges, user interaction. Successful exploitation leads to low impact to confidentiality, low impact to integrity.

Its EPSS score of 5.1% reflects a lower probability of exploitation activity in the wild over the next 30 days, placing it above 91% of all scored CVEs.

Check your external exposure to CVE-2021-27889

Confirm whether Mybb Mybb is running on any internet-facing host or subdomain.
Match discovered service fingerprints against the version affected by CVE-2021-27889.
Prioritise remediation if the asset is public, business-critical, or near authentication/payment flows.

How ThreatPort helps with CVE-2021-27889

ThreatPort's external attack surface scanner checks your internet-facing assets — agentlessly, from the outside in — for the exposed services and versions that CVE-2021-27889 affects, then prioritises the finding by real risk using CISA KEV and FIRST.org EPSS.

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Are you exposed to CVE-2021-27889?

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