# CVE-2026-102356: Kroki Mermaid companion SSRF via flowchart image URLs

Status: published. Published: 2026-11-06. Updated: 2026-11-09.

Kroki creates diagrams from textual descriptions. From 0.26.0 until 0.31.2, the optional Mermaid companion's mermaid/src/worker.js renders attacker-controlled flowchart image nodes in headless Chromium without a network request policy, even when KROKI_SAFE_MODE is set to secure. An actor who can submit Mermaid source and satisfy any authentication or authorization configured by the deployment can cause the companion to issue HTTP or HTTPS GET requests when requesting PNG output. Exploitation requires the Mermaid companion, PNG rendering through its headless Chromium process, a diagram-submission path available to the actor, and network reachability from the companion to the target. The demonstrated impact is limited to blind request reachability and possible state-changing GET endpoints; response exfiltration, cloud metadata access, port scanning, and access beyond the companion's network reachability are not established. This issue is fixed in version 0.31.2.

## Remediation

- fix: io.kroki:kroki-server (maven): GitHub reports patched versions 0.31.2. Check the advisory for the affected release branch. (source: GitHub GHSA-px99-rjv4-49g8) — https://github.com/yuzutech/kroki/security/advisories/GHSA-px99-rjv4-49g8

## Affected products and versions

- yuzutech / kroki: >= 0.26.0, < 0.31.2 (affected). Source: CNA: GitHub_M
-  / io.kroki:kroki-server (io.kroki:kroki-server): >= 0.26.0, <= 0.31.1 (affected, GitHub advisory range). Source: GitHub GHSA-px99-rjv4-49g8

## Severity and prioritization

- CVSS 3.1: 5 (medium); CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:N/A:N; source: CNA: GitHub_M

- CVSS 3.1: 5 (medium); CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:N/A:N; source: NVD: security-advisories@github.com

- CISA KEV: No listing in collected sources

- EPSS: 0.23% as of 2026-11-09; percentile 14.42%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-918

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/yuzutech/kroki/security/advisories/GHSA-px99-rjv4-49g8 (CNA: GitHub_M; x_refsource_CONFIRM)

- https://github.com/yuzutech/kroki/commit/428ea380bc7db9da5c7947f908851c8461d51f82 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/yuzutech/kroki/releases/tag/v0.31.2 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/yuzutech/kroki/commit/428ea380bc7db9da5c7947f908851c8461d51f82 (security-advisories@github.com)

- https://github.com/yuzutech/kroki/releases/tag/v0.31.2 (security-advisories@github.com)

- https://github.com/yuzutech/kroki/security/advisories/GHSA-px99-rjv4-49g8 (security-advisories@github.com)

- https://github.com/yuzutech/kroki/security/advisories/GHSA-px99-rjv4-49g8 (GitHub Security Advisories; advisory)

## Provenance

- CNA: GitHub_M: https://www.cve.org/CVERecord?id=CVE-2026-102356; retrieved 2026-11-09; source updated 2026-11-09

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-102356; retrieved 2026-11-10; source updated 2026-11-09

- GitHub Security Advisories: https://github.com/yuzutech/kroki/security/advisories/GHSA-px99-rjv4-49g8; retrieved 2026-11-08; source updated 2026-09-28

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-102356; retrieved 2026-11-09; source updated Not reported

Revision: 351e1e30dcefba5881d6e93af44e0d212d56fef853840e6db006686602ae2334

Canonical: https://y2.dev/cve/CVE-2026-102356

## Agent and API access

Public CVE pages, Markdown, and JSON are free to read without an account or API key.

- Public catalog: https://y2.dev/cve/index.json. Follow nextCursor with the same search, filters, sort, and limit (1–100). A null cursor marks the end.

- WebMCP: search_cve_disclosures, get_cve_disclosure, get_cve_page_markdown, get_y2_cve_access. Available in compatible browsers.

- Cyber API: https://api.y2.dev/api/v2/cyber/cves and https://api.y2.dev/api/v2/cyber/cves/{cveId}.

- Y2 Pro or Elite: create a workspace API key with the intel:cyber scope and send Authorization: Bearer <Y2_API_KEY>. Setup: https://y2.dev/docs/api/create-key.

- x402: Pay per request without an account or API key. Omit Authorization, read the HTTP 402 PAYMENT-REQUIRED challenge, validate its current requirements, and retry with PAYMENT-SIGNATURE through an authorized payment client. These browser tools never make payments. Guide: https://y2.dev/docs/api/x402.

- OpenAPI: https://y2.dev/api/openapi.yaml. Agent access metadata: https://y2.dev/cve/agent.json.

Collected public records only. Check source status for coverage and freshness.