CVE-2026-45119Network attack vector

Service interrupt via forged conversion request

Published Aug 18, 2026 · Updated Aug 19, 2026

CSRF in MyBB before 1.8.40 allows same-site attackers to alter table encoding and interrupt service via a crafted Admin CP URL. In admin/modules/tools/system_health.php, the UTF-8 Conversion do=all path accepts GET requests naming a table and runs ALTER TABLE, column rewrite, and fulltext index rebuild work without verify_post_check validation. Exploitation requires an authenticated Admin CP user to load attacker-controlled content in the same site context; the published impact is limited to schema changes and denial of service, not data disclosure.

CVSS severity4.6
Medium
EPSS probability0.13%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

CSRF in MyBB before 1.8.40 allows same-site attackers to alter table encoding and interrupt service via a crafted Admin CP URL. In admin/modules/tools/system_health.php, the UTF-8 Conversion do=all path accepts GET requests naming a table and runs ALTER TABLE, column rewrite, and fulltext index rebuild work without verify_post_check validation. Exploitation requires an authenticated Admin CP user to load attacker-controlled content in the same site context; the published impact is limited to schema changes and denial of service, not data disclosure.

The record

CVE
CVE-2026-45119
Published
Aug 18, 2026
Updated
Aug 19, 2026
Vendor
MyBB Group
Product
MyBB
Classifications
CWE-352
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 18, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 19, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 1.8.40

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

MyBB Group · MyBBversion=< 1.8.40

Published CVSS scores

4.6GitHub_M CNACVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:L

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.

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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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-352Cross-Site Request Forgery (CSRF)

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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