CVE-2026-63429Public exploitNetwork attack vector

Unauthenticated file hosting via unguarded upload endpoint

Published Jul 20, 2026 · Updated Jul 20, 2026

Unrestricted file upload in HeyForm before 3.0.0-rc.9 allows remote attackers to store arbitrary files through POST /api/upload. UploadController accepts multipart files without an authentication guard, session cookie, openToken, or binding the request to a form. No account or user interaction is required; accepted files receive public URLs, enabling attacker-controlled hosting and storage exhaustion.

CVSS severity8.6
High
EPSS probability0.51%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Unrestricted file upload in HeyForm before 3.0.0-rc.9 allows remote attackers to store arbitrary files through POST /api/upload. UploadController accepts multipart files without an authentication guard, session cookie, openToken, or binding the request to a form. No account or user interaction is required; accepted files receive public URLs, enabling attacker-controlled hosting and storage exhaustion.

The record

CVE
CVE-2026-63429
Published
Jul 20, 2026
Updated
Jul 20, 2026
Vendor
HeyForm
Product
HeyForm
Classifications
CWE-306, CWE-434, T1608.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 20, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 20, 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=< 3.0.0-rc.9

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

HeyForm · HeyFormversion=< 3.0.0-rc.9

Published CVSS scores

9.4GitHub Security AdvisoryCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:H
8.6GitHub CNACVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/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.

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 exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-306Missing Authentication for Critical Function
CWE-434Unrestricted Upload of File with Dangerous Type
T1608.001Upload Malware

Public exploit references

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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