CVE-2021-27890Known exploitationPublic exploitNetwork attack vector

SQL injection via uncoerced templateset property

Published Mar 15, 2021 · Updated Aug 3, 2024

SQL injection in MyBB before 1.8.26 allows attackers to alter database queries through malicious theme XML properties. The templateset property is stored from imported theme XML and later concatenated without integer coercion into template-selection queries in theme administration and rendering paths. Exploitation requires a theme-capable administrator to import the crafted XML and then export or duplicate the theme, or a user assigned the theme to visit a forum page; chaining the database write into template evaluation enables code execution.

CVSS severity8.8
High
EPSS probability10.59%
Next 30 days · Sep 16, 2026
Known exploitationReported
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

SQL injection in MyBB before 1.8.26 allows attackers to alter database queries through malicious theme XML properties. The templateset property is stored from imported theme XML and later concatenated without integer coercion into template-selection queries in theme administration and rendering paths. Exploitation requires a theme-capable administrator to import the crafted XML and then export or duplicate the theme, or a user assigned the theme to visit a forum page; chaining the database write into template evaluation enables code execution.

The record

CVE
CVE-2021-27890
Published
Mar 15, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-89, T1204.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 15, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

6.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:P
8.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationReported
Public exploitPublished

Weakness, pattern, technique

CWE-89Improper Neutralization of Special Elements used in an SQL Command ('SQL Injection')
T1204.002User Execution: Malicious File

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Reported exploitation

Technologies

Your stack

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Your stack

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