CVE-2026-29183: SiYuan: Unauthenticated Reflected XSS via SVG Injection in /api/icon/getDynamicIcon Endpoint

Should you act?

Critical and remotely reachable

No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
• EPSS 0.7%, percentile 52: FIRST’s model estimates a 0.7% chance of exploitation activity in the next 30 days, higher than 52% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
• Needs a user to click or open something. Phishing makes that realistic, but it is not wormable.
• Only applies if your dependency tree includes github.com/siyuan-note/siyuan/kernel (Go) < 0.0.0-20260304034809-d68bd5a79391, fixed in 0.0.0-20260304034809-d68bd5a79391. Check your lockfile, including transitive dependencies.

What it is

SiYuan is a personal knowledge management system. Prior to version 3.5.9, an unauthenticated reflected XSS vulnerability exists in the dynamic icon API endpoint "GET /api/icon/getDynamicIcon" when type=8, attacker-controlled content is embedded into SVG output without escaping. Because the endpoint is unauthenticated and returns image/svg+xml, a crafted URL can inject executable SVG/HTML event handlers (for example onerror) and run JavaScript in the SiYuan web origin. This can be chained to perform authenticated API actions and exfiltrate sensitive data when a logged-in user opens the malicious link. This issue has been patched in version 3.5.9.

From the GitHub advisory

Summary An unauthenticated reflected XSS vulnerability exists in the dynamic icon API endpoint:

- GET /api/icon/getDynamicIcon

When type=8, attacker-controlled content is embedded into SVG output without escaping. Because the endpoint is unauthenticated and returns image/svg+xml, a crafted URL can inject executable SVG/HTML event handlers (for example onerror) and run JavaScript in the SiYuan web origin.

This can be chained to perform authenticated API actions and exfiltrate sensitive data when a logged-in user opens the malicious link.

Details The issue is caused by unsafe output construction and incomplete sanitization:

Weakness type: CWE-79.

Product: github.com/siyuan-note/siyuan/kernel (Go) · Assigned by: GitHub_M · Published: 2026-03-06

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: none (no login)
• User interaction: required (a user must click/open something)
• Scope: changed (can affect other components)

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation none, automatable no, technical impact total.
• FIRST EPSS (model of 2026-10-21): 0.69% probability of exploitation activity in the next 30 days; percentile 52.

Timeline

• 2026-03-04 — GitHub-reviewed advisory GHSA-6865-qjcf-286f published (critical)
• 2026-03-06 — CVE record last updated
• 2026-03-06 — CVE record published by GitHub_M

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-6865-qjcf-286f github.com
2. CVE.org record CVE-2026-29183 cve.org
3. NVD entry CVE-2026-29183 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com

Critical Go advisories · Today’s Security Digest