CVE-2026-55660Network attack vector

Session takeover via unchecked cross-origin messages

Published Jul 1, 2026 · Updated Jul 1, 2026

Origin validation errors in TinaCMS before 3.9.3 allow remote attackers to take over authenticated editing sessions through forged messages. The useTina overlay, OAuth popup, and admin-to-preview GraphQL handlers process event.data without checking event.origin or event.source and send replies to non-specific origins. Exploitation requires an editor to visit an attacker-controlled page or maintain an opener or iframe relationship, after which forged messages can drive the editor, inject preview content, or compromise the session.

CVSS severity8.5
High
EPSS probability0.28%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Origin validation errors in TinaCMS before 3.9.3 allow remote attackers to take over authenticated editing sessions through forged messages. The useTina overlay, OAuth popup, and admin-to-preview GraphQL handlers process event.data without checking event.origin or event.source and send replies to non-specific origins. Exploitation requires an editor to visit an attacker-controlled page or maintain an opener or iframe relationship, after which forged messages can drive the editor, inject preview content, or compromise the session.

The record

CVE
CVE-2026-55660
Published
Jul 1, 2026
Updated
Jul 1, 2026
Vendor
TinaCMS
Product
@tinacms/app
Classifications
CWE-79, CWE-601, CWE-346, CWE-940, T1189
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 1, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 1, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 2.5.6

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

TinaCMS · @tinacms/appversion=< 2.5.6
TinaCMS · TinaCMSversion=< 3.9.3

Published CVSS scores

8.5GitHubCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:N/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 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 exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CWE-601URL Redirection to Untrusted Site ('Open Redirect')
CWE-346Origin Validation Error
CWE-940Improper Verification of Source of a Communication Channel
T1189Drive-by Compromise

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

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo