CVE-2026-84803
Stored XSS in SiYuan < v3.8.2 allows JS execution via crafted uploaded files.
Is CVE-2026-84803 being exploited?
Not confirmed. CVE-2026-84803 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.23% probability of exploitation in the next 30 days.
How severe is CVE-2026-84803?
CVE-2026-84803 is rated High with a CVSS score of 8.6. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-84803?
Yes. A fix has been recorded for CVE-2026-84803. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-84803 affect?
CVE-2026-84803 affects SiYuan < 3.8.2, SiYuan self-hosted instances, SiYuan desktop/web deployments. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-84803?
Upgrade to v3.8.2, remove untrusted uploads, rotate exposed API tokens.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Stored XSS via script-capable uploaded files; attackers can run JS in users' browsers, steal API tokens and hijack workspaces/sessions.
Immediate action required
- affected< 3.8.2
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.