CVE-2026-87811

Exploitation

Public exploit code exists. CISA's assessment records a public proof of concept. That is not a report of exploitation in the wild.

SSVC decision

• ExploitationpocPublic proof-of-concept exploit code exists. Not a report of exploitation in the wild.
• AutomatablenoAt least one step from reconnaissance to exploitation cannot be reliably automated.
• Technical ImpacttotalSuccessful exploitation gives total control of the vulnerable component.

CISA publishes the decision points, not a final SSVC decision. The decision also depends on mission and well-being impact, which is a property of your deployment rather than of the vulnerability.

EPSS probability

0.36% probability of exploitation activity in the next 30 days.

EPSS percentile

Equal to or higher than the score of 30.2% of scored records. A rank, not a probability.

NVD base score

8.4 (CVSS v4.0), scored by the NVD independently of the CNA.

NVD CVSS vector

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/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

NVD analysis status

Deferred. NVD last modified this record on 2026-09-09.

Red Hat severity

No Red Hat rating. Red Hat rates the CVEs that affect its products.

Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.

Published

2026-09-09 11:20Z1 MO AGO

Last updated

2026-09-09 12:19Z1 MO AGO

Reserved

2026-09-09

Assigning CNA

VulnCheck

Record state

PUBLISHED

Severity

High (CVSS 8.4)

CNA CVSS vector

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

Weaknesses

• CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')Base

Data version

5.2

Document digest

e23ededa2acac65504cb990b861604b9c945a9a68e719d39c33a9aea05b3f23b

• github.comGitHub Security Advisory (GHSA-v6wf-r2gr-rrgf)https://github.com/siyuan-note/siyuan/security/advisories/GHSA-v6wf-r2gr-rrgfvendor-advisory
• www.vulncheck.comVulnCheck Advisory: SiYuan before v3.8.2 Stored XSS via notebook template pathshttps://www.vulncheck.com/advisories/siyuan-before-3.8.2-stored-xss-via-notebook-template-pathsthird-party-advisory