CVE-2026-43900: DeepChat SVG Artifact XSS via Sanitizer Bypass
CVE-2026-43900 is a critical cross-site scripting flaw in DeepChat, an open-source AI agent platform, affecting versions before v1.0.4-beta.1. The SVG sanitizer removes javascript: protocols with plain-text regular expressions and does not account for HTML entity decoding before Vue's v-html rendering. The advisory says it is fixed in v1.0.4-beta.1, and the sources consulted show no confirmed exploitation.
Overview
DeepChat is an open-source AI agent platform. According to the GitHub Security Advisory, a cross-site scripting issue exists in versions before v1.0.4-beta.1 because the SVG sanitizer validates content differently from how the browser renders it. The record classifies the weakness as CWE-79.
Impact
- The advisory describes arbitrary JavaScript execution in the victim's browser context when the victim interacts with a rendered SVG artifact.
- The record assigns a CVSS 3.1 base score of 9.3 (critical), with high confidentiality and integrity impact and no availability impact, requiring user interaction.
- The scope is marked as changed in the CVSS data, which is consistent with script running beyond the vulnerable component.
Affected products and versions
- The advisory states the flaw affects DeepChat releases prior to v1.0.4-beta.1.
- The structured affected-product list in the record is empty, so the exact product identifiers and version ranges should be confirmed in the GitHub advisory.
Exploitation status
The record shows that this CVE is not listed in the CISA Known Exploited Vulnerabilities catalog. No confirmed exploitation appears in the sources consulted. The EPSS probability is 0.00502, which is a statistical estimate and not evidence of exploitation.
Remediation and mitigation
- Upgrade DeepChat to v1.0.4-beta.1 or a later release, as stated in the advisory.
- Until the upgrade is complete, avoid opening SVG artifacts from untrusted sources in DeepChat, and limit which users can supply content that is rendered.
- Where feasible, treat rendered SVG content as untrusted active content and reduce the trust placed in client-side sanitization alone.
Detection guidance
- Review stored SVG artifacts for unexpected protocol-like strings or encoded character references in attribute and link contexts.
- Monitor application logs and the front-end for unusual SVG artifact creation or rendering activity, recognizing that the sources do not describe specific indicators.
Limitations of the available information
The record does not include a structured list of affected or fixed versions, vendor-supplied patch details beyond the advisory text, or proof-of-concept details. The EPSS date in the record is later than the publication date, so its timing should be verified against the source. Whether other components are affected is unknown from the sources consulted.
Frequently asked questions
What is CVE-2026-43900?
It is a critical cross-site scripting vulnerability in DeepChat, caused by an SVG sanitizer that does not account for HTML entity decoding before rendering. The advisory says it is fixed in v1.0.4-beta.1.
Which versions are affected?
According to the advisory, versions prior to v1.0.4-beta.1 are affected. The structured affected-version data in the record is empty, so the GitHub advisory should be checked for exact details.
Is this vulnerability being actively exploited?
The record shows it is not listed in CISA's Known Exploited Vulnerabilities catalog, and no confirmed exploitation appears in the sources consulted.
What should administrators do?
Upgrade DeepChat to v1.0.4-beta.1 or later, and avoid opening SVG artifacts from untrusted sources until the upgrade is complete.
This analysis was drafted with AI assistance from verified source data and automatically checked against it.