CVE-2026-72583Network attack vector

Stored XSS via client-controlled MIME validation

Published Aug 10, 2026 · Updated Aug 10, 2026

Stored XSS in FastSchema 0 through 0.15.1 allows remote authenticated users to store script-bearing SVG files via uploads. The PutMultipart function in pkg/rclonefs/base.go trusts the client-supplied Content-Type header instead of inspecting file contents, so a renamed .jpg can carry SVG JavaScript into the web root. Low-privileged access to the upload route and a victim opening the stored asset are required; the script then runs in the victim's browser origin.

CVSS severity5.4
Medium
EPSS probability0.15%
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 FastSchema 0 through 0.15.1 allows remote authenticated users to store script-bearing SVG files via uploads. The PutMultipart function in pkg/rclonefs/base.go trusts the client-supplied Content-Type header instead of inspecting file contents, so a renamed .jpg can carry SVG JavaScript into the web root. Low-privileged access to the upload route and a victim opening the stored asset are required; the script then runs in the victim's browser origin.

The record

CVE
CVE-2026-72583
Published
Aug 10, 2026
Updated
Aug 10, 2026
Vendor
FastSchema
Product
FastSchema
Classifications
CWE-79, T1059.007
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 10, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 10, 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=0 <=0.15.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

FastSchema · FastSchemaversion=0 <=0.15.1

Published CVSS scores

5.4TuranSecCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A: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')
T1059.007JavaScript/JScript

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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