Security readout for executives and security teams
Plain-English summary
SiYuan versions before 3.8.1 can store unsafe content in block names, aliases, or memos. When another user encounters the affected block through document hints, backlinks, or breadcrumbs, attacker-controlled script may run in that user’s browser, potentially compromising information and actions available through their session.
Executive priority
Treat internet-accessible or multi-user affected deployments as an immediate remediation priority. Upgrade promptly and temporarily reduce untrusted editing access. Although active exploitation is not documented, stored script execution across user sessions creates substantial confidentiality and integrity risk.
Technical view
This is stored cross-site scripting caused by insufficient output escaping in hint, backlink, and breadcrumb rendering. A low-privileged attacker can place HTML or script content in block metadata; exploitation then requires another user to view an affected rendering context. The published CVSS 4.0 score is 9.3, with high confidentiality and integrity impact.
Likely exposure
Exposure is most likely in multi-user SiYuan deployments running versions earlier than 3.8.1 where untrusted or lower-privileged users can edit block names, aliases, or memos. Risk increases when other users routinely view documents containing references, backlinks, hints, or breadcrumbs for attacker-controlled blocks.
Exploitation context
The sources describe a network-accessible, low-complexity attack requiring low privileges and passive victim interaction. The malicious content persists and executes when rendered to another user. This CVE is not identified as KEV, and the supplied sources provide no evidence of active exploitation in the wild.
Researcher notes
CWE-79 applies. Relevant sinks are the hint, backlink, and breadcrumb rendering functions; relevant stored inputs are block name, alias, and memo fields. The supplied evidence does not identify specific commits, observed attacks, affected deployment modes, or indicators of compromise, so those details should not be inferred.
Mitigation direction
- Upgrade affected SiYuan installations to version 3.8.1 or later, following vendor guidance.
- Restrict untrusted users from editing block names, aliases, and memos until upgraded.
- Limit access to affected collaborative instances where immediate upgrading is unavailable.
- Review the vendor advisory for any additional remediation or release-specific instructions.
Validation and detection
- Inventory every SiYuan deployment and confirm its installed version.
- Verify upgraded systems report version 3.8.1 or later.
- Review permissions for users who can edit block metadata.
- Inspect block names, aliases, and memos for unexpected HTML or script-like content.
- Safely regression-test that harmless markup is encoded in hints, backlinks, and breadcrumbs.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-79: User-session and phishing behavior lookup
Client-side and session-facing weaknesses should be reviewed alongside initial-access and user-execution behaviors. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2026-82654 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Critical
- CVSS
- 9.3 (4.0)
- Known Exploited
- No
- Published
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:H/VI:H/VA:L/SC:H/SI:H/SA:L
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
SSVC decision data
CVSS vector scores
2 official scoresWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:H/VI:H/VA:L/SC:H/SI:H/SA:L——VulnCheckCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:L2.36VulnCheckVulnerability scoring details
Base CVSS 4.0 score
9.3CriticalVector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:H/VI:H/VA:L/SC:H/SI:H/SA:L
Base CVSS 3.1 score
8.9HighVector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:L
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- GitHub Security Advisory (GHSA-hf87-qh3j-3p88)CVE reference, VulnCheck · vendor-advisory
- VulnCheck Advisory: SiYuan before v3.8.1 Stored XSS via block nameCVE reference, VulnCheck · third-party-advisory
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.