CVE-2026-56299Public exploitNetwork attack vector

Service interruption via unauthenticated OPTIONS request

Published Jun 21, 2026 · Updated Jun 21, 2026

Authentication bypass in Capgo's build-upload API before 12.128.2 allows remote attackers to interrupt service via an OPTIONS request. The OPTIONS route for /build/upload/:jobId/* skips middlewareKey and passes a synthetic empty API-key object to tusProxy, whose downstream state handling returns HTTP 500 even for nonexistent jobs. No authentication or valid job identifier is required; repeated requests cause application-layer request flooding and log amplification.

CVSS severity6.9
Medium
EPSS probability0.68%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authentication bypass in Capgo's build-upload API before 12.128.2 allows remote attackers to interrupt service via an OPTIONS request. The OPTIONS route for /build/upload/:jobId/* skips middlewareKey and passes a synthetic empty API-key object to tusProxy, whose downstream state handling returns HTTP 500 even for nonexistent jobs. No authentication or valid job identifier is required; repeated requests cause application-layer request flooding and log amplification.

The record

CVE
CVE-2026-56299
Published
Jun 21, 2026
Updated
Jun 21, 2026
Vendor
Capgo
Product
Capgo
Classifications
CWE-306, CWE-755, T1499.003
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 21, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 21, 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 <12.128.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Capgo · Capgoversion=0 <12.128.2

Published CVSS scores

6.9VulnCheckCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
5.3VulnCheckCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 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-755Improper Handling of Exceptional Conditions
T1499.003Application Exhaustion Flood

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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