CVE-2026-34226Public exploitNetwork attack vector

Cookie disclosure via page-origin fetch lookup

Published Mar 27, 2026 · Updated Mar 27, 2026

Information disclosure in capricorn86 Happy DOM before 20.8.9 allows remote attackers to leak page-origin cookies in cross-origin fetches. FetchRequestHeaderUtility.getRequestHeaders passes an originURL derived from window.location to cookieContainer.getCookies instead of using the request URL. Exploitation requires credentials include, distinct page and destination origins, and a page-origin cookie; the destination receives that cookie.

CVSS severity7.5
High
EPSS probability0.46%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Information disclosure in capricorn86 Happy DOM before 20.8.9 allows remote attackers to leak page-origin cookies in cross-origin fetches. FetchRequestHeaderUtility.getRequestHeaders passes an originURL derived from window.location to cookieContainer.getCookies instead of using the request URL. Exploitation requires credentials include, distinct page and destination origins, and a page-origin cookie; the destination receives that cookie.

The record

CVE
CVE-2026-34226
Published
Mar 27, 2026
Updated
Mar 27, 2026
Vendor
capricorn86
Product
Happy DOM
Classifications
CWE-201, T1539
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 27, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 27, 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=< 20.8.9

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

capricorn86 · Happy DOMversion=< 20.8.9

Published CVSS scores

7.5GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/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.

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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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-201Insertion of Sensitive Information Into Sent Data
T1539Steal Web Session Cookie

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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