Application logic corruption via __proto__ parent identifier
Published Aug 6, 2026 · Updated Aug 6, 2026
Prototype pollution in Mermaid Architecture Diagrams 11.5.0 through 11.16.0 allows remote authenticated users to corrupt application logic. The parser accepts proto as a parent group identifier and writes a horizontal or vertical service direction through that key onto Object.prototype. Remote authenticated users must be able to submit untrusted architecture-beta diagram text; the polluted property can corrupt defaults, bypass truthiness checks, interrupt processing, or alter embedding-application logic.
Summary
What happened
Prototype pollution in Mermaid Architecture Diagrams 11.5.0 through 11.16.0 allows remote authenticated users to corrupt application logic. The parser accepts proto as a parent group identifier and writes a horizontal or vertical service direction through that key onto Object.prototype. Remote authenticated users must be able to submit untrusted architecture-beta diagram text; the polluted property can corrupt defaults, bypass truthiness checks, interrupt processing, or alter embedding-application logic.
The record
- CVE
- CVE-2026-71437
- Published
- Aug 6, 2026
- Updated
- Aug 6, 2026
- Vendor
- Mermaid
- Product
- Mermaid
- Classifications
- CWE-1321
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Aug 6, 2026CVE publishedPublication date reported by the CVE source.
- Aug 6, 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.
- Affected versionversion=>= 11.5.0, < 11.16.1
What conditions does exploitation require?
What is affected?
Published CVSS scores
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.
Weakness, pattern, technique
Public exploit references
- GHSA-3rrr-jr9j-h3q3 architecture-beta proof of conceptproof of concept · demonstrated
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