CVE-2026-44657Network attack vector

Browser script execution via unsafe inline attachments

Published May 28, 2026 · Updated May 28, 2026

Stored XSS in file_download.php in MantisBT before 2.28.2 allows remote authenticated users to execute JavaScript in a victim's browser. The endpoint serves attacker-uploaded XHTML inline with an active MIME type, allowing that document to reference and run a separately uploaded JavaScript attachment. Exploitation requires upload privileges, show_inline=1, a valid file_show_inline_token CSRF token, and passive interaction by a user who opens the crafted attachment.

CVSS severity7.5
High
EPSS probability0.35%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored XSS in file_download.php in MantisBT before 2.28.2 allows remote authenticated users to execute JavaScript in a victim's browser. The endpoint serves attacker-uploaded XHTML inline with an active MIME type, allowing that document to reference and run a separately uploaded JavaScript attachment. Exploitation requires upload privileges, show_inline=1, a valid file_show_inline_token CSRF token, and passive interaction by a user who opens the crafted attachment.

The record

CVE
CVE-2026-44657
Published
May 28, 2026
Updated
May 28, 2026
Vendor
MantisBT
Product
MantisBT
Classifications
CWE-79, T1203
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. May 28, 2026CVE publishedPublication date reported by the CVE source.
  2. May 28, 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=< 2.28.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

MantisBT · MantisBTversion=< 2.28.2

Published CVSS scores

7.5GitHub Security AdvisoryCVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1203Exploitation for Client Execution

Public exploit references

No public exploit references are available in this record.

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

Technologies

Your stack

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Your stack

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