EUVD-2026-54242
GHSA-3rrr-jr9j-h3q3
Severity by source
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Network-reachable via untrusted diagram input, no auth or interaction needed for automated rendering, scope changed because pollution crosses into the embedding application's realm.
AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
Primary rating from Vendor (https://github.com/mermaid-js/mermaid).
CVSS VectorVendor: https://github.com/mermaid-js/mermaid
Lifecycle Timeline
3Blast Radius
ecosystem impact- 1 npm packages depend on mermaid (1 direct, 0 indirect)
Ecosystem-wide dependent count for version 11.5.0.
DescriptionCVE.org
Rendering an untrusted architecture-beta diagram lets the diagram author write an arbitrary property with the value horizontal or vertical onto Object.prototype. A group id of __proto__ is accepted as a valid parent.
Impact
Any code in the same realm that reads a property of that name from an arbitrary object, or enumerates an object with bare for...in, observes the injected value (which can only be the string horizontal or vertical.
This may mean corrupted option/config defaults, bypassed truthiness checks, causing denial of service or logic corruption in the embedding application.
Because the injected value cannot be an object or function, this is not directly exploitable for remote code execution.
PoC
architecture-beta
group mermaidPrototypePollutionMarker(cloud)[Marker]
service a(server)[A] in __proto__
service b(server)[B] in mermaidPrototypePollutionMarker
a:R -- L:bThe vulnerable write was introduced in commit cb0a4703bdf01d47508bde1c08aa9a980d70bc20 and first shipped in mermaid@11.5.0. The lines are unchanged in every release since.
Patches
This has been patched by https://github.com/mermaid-js/mermaid/commit/99af3fc35ef0a9a9c8c6314521344d67523ddccf, released in Mermaid v11.16.1
Workarounds
There are no known workarounds. Please update to a patched version.
References
_Are there any links users can visit to find out more?_
- https://github.com/mermaid-js/mermaid/commit/99af3fc35ef0a9a9c8c6314521344d67523ddccf
- https://github.com/mermaid-js/mermaid/releases/tag/mermaid%4011.16.1
AnalysisAI
Prototype pollution in Mermaid's architecture-beta diagram renderer (mermaid@11.5.0 through 11.16.0) allows an untrusted diagram author to write the string 'horizontal' or 'vertical' directly onto Object.prototype by supplying '__proto__' as a valid group parent identifier. All JavaScript code sharing the same runtime realm that reads or enumerates the injected property name may observe corrupted option defaults, bypassed truthiness checks, or denial-of-service conditions in the embedding application. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires two concrete conditions: first, the application must accept untrusted Mermaid diagram source text and pass it to the Mermaid renderer without stripping or validating diagram type; second, the diagram must use the 'architecture-beta' diagram type (diagrams using other Mermaid types such as flowchart, sequence, or gantt are not affected by this vulnerability). … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | No CVSS score or EPSS probability was provided for this CVE, so quantitative risk ranking is not possible. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Upgrade to mermaid@11.16.1 or later, which resolves this issue by replacing prototype-vulnerable plain-object group storage with ES6 Map and Set structures (commit 99af3fc35ef0a9a9c8c6314521344d67523ddcommit, PR https://github.com/mermaid-js/mermaid/pull/8022; release notes at https://github.com/mermaid-js/mermaid/releases/tag/mermaid%4011.16.1). … Detailed patch versions, workarounds, and compensating controls in full report. |
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View allVendor StatusVendor
SUSE
Severity: ModerateShare
External POC / Exploit Code
Leaving vuln.today