Configuration corruption via unsafe recursive object merge
Published Aug 6, 2026 · Updated Aug 6, 2026
Prototype pollution in Mermaid before 10.9.8 and 11.0.0-alpha.1 through 11.16.0 allows attackers to modify object prototype properties. The mermaid.initialize, mermaidAPI.setConfig, and mermaidAPI.updateSiteConfig entry points pass caller-supplied objects to assignWithDepth, whose recursive merge does not block prototype keys. Exploitation requires an integrating application to forward untrusted data directly into these trusted-configuration APIs; diagram directives and YAML frontmatter are not affected.
Summary
What happened
Prototype pollution in Mermaid before 10.9.8 and 11.0.0-alpha.1 through 11.16.0 allows attackers to modify object prototype properties. The mermaid.initialize, mermaidAPI.setConfig, and mermaidAPI.updateSiteConfig entry points pass caller-supplied objects to assignWithDepth, whose recursive merge does not block prototype keys. Exploitation requires an integrating application to forward untrusted data directly into these trusted-configuration APIs; diagram directives and YAML frontmatter are not affected.
The record
- CVE
- CVE-2026-71438
- Published
- Aug 6, 2026
- Updated
- Aug 6, 2026
- Vendor
- Mermaid
- Product
- Mermaid
- Classifications
- CWE-1321
- Attack vector
- local
- Privileges
- admin
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=< 10.9.8
- Affected versionversion=>= 11.0.0-alpha.1, < 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
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