VulnerabilityPublished 16 Jan 2026

CVE-2026-23645: siyuan · Cross-site Scripting

Affects siyuanSource CVE Database V5

Not known to be exploited · CVSS 5.3 Medium : upgrade to 3.5.4-dev2 when convenient.

Data as of 26 Oct 2026, 17:16 UTC

CVSS 4.0 base score

5.3Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.2% chance of exploitation in 30 days – higher than 20% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 3.5.4-dev2

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

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: None
User Interaction: Passive
Vulnerable system confidentiality: None
Vulnerable system integrity: None
Vulnerable system availability: None
Subsequent system confidentiality: Low
Subsequent system integrity: Low
Subsequent system availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: Passive: Successful exploitation of this vulnerability requires limited interaction by the targeted user with the vulnerable system and the attacker’s payload. These interactions would be considered involuntary and do not require that the user actively subvert protections built into the vulnerable system.
Vulnerable system confidentiality: None: There is no loss of confidentiality within the Vulnerable System.
Vulnerable system integrity: None: There is no loss of integrity within the Vulnerable System.
Vulnerable system availability: None: There is no impact to availability within the Vulnerable System.
Subsequent system confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the Subsequent System.
Subsequent system integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact to the Subsequent System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 16 Jan 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade siyuan to 3.5.4-dev2.

Affected software

Product	Affected	Fixed in
siyuan-notesiyuan	Affected <3.5.4-dev2	Fixed in 3.5.4-dev2
GitHubsiyuan-note/siyuan`pkg:github/siyuan-note/siyuan`Other threats	Affected =3.5.4-dev2	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Upgrade SiYuan Note to version 3.5.4-dev2 or later immediately to apply the official fix that sanitizes SVG uploads.
Implement strict file upload policies restricting SVG uploads to trusted users or disabling SVG uploads entirely if not required.
Employ server-side SVG sanitization tools that remove or neutralize embedded scripts before storage or rendering.
Educate users on the risks of opening untrusted SVG files and encourage caution with files from unknown sources.
Monitor application logs for unusual upload or viewing activity related to SVG files.
Use Content Security Policy (CSP) headers to restrict script execution contexts and reduce the impact of potential XSS attacks.
Consider isolating the SiYuan Note environment or running it in a sandboxed container to limit the scope of compromise.
Regularly audit and update all self-hosted applications to ensure timely patching of vulnerabilities.

Description

CVE-2026-23645 is a stored Cross-Site Scripting (XSS) vulnerability in SiYuan Note versions prior to 3.5.4-dev2. The flaw arises because the application fails to sanitize uploaded SVG files, allowing malicious JavaScript embedded in SVGs to execute in the context of an authenticated user's session. Exploitation requires a user to upload and then view a crafted SVG file, leading to arbitrary script execution without requiring authentication or elevated privileges. The vulnerability has a CVSS 4.0 base score of 5.3, indicating medium severity. There are no known exploits in the wild as of now. European organizations using SiYuan Note for personal knowledge management should upgrade to version 3.

Impact

For European organizations, the impact of this vulnerability can be significant, especially for those relying on SiYuan Note for knowledge management and collaboration. Successful exploitation can lead to session hijacking, unauthorized data access, and potential lateral movement within internal networks. Confidentiality is at risk as attackers can steal sensitive information accessible through the user's session. Integrity may be compromised if attackers perform unauthorized actions or inject malicious content. Availability impact is limited but could occur if attackers disrupt user sessions or application functionality. Given that exploitation requires user interaction (viewing a malicious SVG), the risk is mitigated somewhat but remains notable due to the ease of embedding SVGs in documents and messages. European organizations with decentralized IT environments or those encouraging self-hosted solutions may be more exposed. The medium CVSS score reflects a moderate risk that should not be ignored, especially in sectors handling sensitive or regulated data. Attackers could leverage this vulnerability as an initial foothold or as part of a broader attack chain targeting knowledge management systems.

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') (opens in a new tab)
Base weaknessLikelihood of exploit: HighCWE Top 25 (2025): #1OWASP Top 10 A05:2025: Injection (opens in a new tab)
The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.
Architecture and Design · Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Implementation · Architecture and Design
Understand the context in which your data will be used and the encoding that will be expected. This is especially important when transmitting data between different components, or when generating outputs that can contain multiple encodings at the same time, such as web pages or multi-part mail messages.
Architecture and Design · Implementation · Attack Surface Reduction
Understand all the potential areas where untrusted inputs can enter your software: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide…
OWASP Cheat Sheets
Cross Site Scripting Prevention (opens in a new tab)
DOM based XSS Prevention (opens in a new tab)
Injection Prevention (opens in a new tab)
Abuse Case (opens in a new tab)
Deserialization (opens in a new tab)
OWASP ASVS 4.0.3
V5.3.3 (opens in a new tab)
V1.5.1 (opens in a new tab)
Attack patterns
XSS Using MIME Type Mismatch (opens in a new tab)
DOM-Based XSS (opens in a new tab)
Reflected XSS (opens in a new tab)
Stored XSS (opens in a new tab)
Cross-Site Scripting (XSS) (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 23 Jan 2026, 20:35 UTC

WeaknessesCWE-79

Technical details

References

Community reviews

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