Cyber Resilience

CVE-2026-56397

CriticalPublic PoC

Published: 21 June 2026

Published
21 June 2026
Modified
24 June 2026
KEV Added
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Patch
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CVSS Score v4 9.4 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/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
EPSS Score 0.0039 31.0th percentile
Risk Priority 70 floored blend · peak EPSS

Summary

CVE-2026-56397 is a critical-severity Cross-site Scripting (CWE-79) vulnerability. Its CVSS base score is 9.4 (Critical).

Operationally, exploitation aligns with the MITRE ATT&CK technique Drive-by Compromise (T1189); ranked at the 31.0th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.

OWASP Top 10 for Web (2025)

A05:2025 Injection

EU & UK References

Vulnerability details

SiYuan before v3.6.1 fails to sanitize package metadata and README content in the Bazaar marketplace, allowing malicious package authors to inject arbitrary HTML and JavaScript. Attackers can achieve remote code execution on any user browsing the Bazaar by embedding XSS…

more

payloads in package displayName, description, or README fields, exploiting Electron's nodeIntegration setting to execute OS commands.

CWE(s)
CWE-79

Related Threats

MITRE ATT&CK Enterprise TechniquesAI

T1189 Drive-by Compromise Initial Access
Adversaries may gain access to a system through a user visiting a website over the normal course of browsing.
attack.mitre.org →
T1195.002 Compromise Software Supply Chain Initial Access
Adversaries may manipulate application software prior to receipt by a final consumer for the purpose of data or system compromise.
attack.mitre.org →
Why these techniques?

XSS in public Bazaar marketplace directly enables drive-by client compromise (T1189) and supply-chain poisoning via unsanitized package metadata (T1195.002) leading to Electron RCE.

Confidence: HIGH · MITRE ATT&CK Enterprise v19.0

Affected Assets

Mitigating Controls

Likely Mitigating Controls AI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

CA-8 Penetration Testing
addresses: CWE-79

Penetration testing submits XSS payloads to web applications, detecting cross-site scripting flaws for subsequent remediation.

SI-10 Information Input Validation
addresses: CWE-79

Validates web inputs to reject script-related content that could produce XSS.

SI-15 Information Output Filtering
addresses: CWE-79

Output validation against expected content can reject or sanitize script content in generated web pages, reducing XSS exploitability.

References