CVE-2026-43899
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedDeepChat is an open-source artificial intelligence agent platform that unifies models, tools, and agents. Prior to v1.0.4-beta.1, An incomplete mitigation for CVE-2025-55733 leaves DeepChat vulnerable to an arbitrary protocol execution bypass (RCE). While the patch correctly restricted api.openExternal() inside the renderer's preload/index.ts script, it structurally neglected to sanitize native Electron pop-up window handlers. An attacker or a compromised AI endpoint returning a Markdown link can trigger a target="_blank" native window interception in tabPresenter.ts, which forwards the malicious URL directly to shell.openExternal(url) and completely bypasses the isValidExternalUrl security boundary. This vulnerability is fixed in v1.0.4-beta.1.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceDeepChat prior to v1.0.4-beta.1 contains an RCE bypass where native Electron pop-up window handlers in tabPresenter.ts fail to validate URLs before passing them to shell.openExternal(). Attackers exploit this by crafting malicious Markdown links that trigger target='_blank' window interception, completely circumventing the isValidExternalUrl security boundary that was fixed for CVE-2025-55733.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- Required
- Scope
- Changed
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Check DeepChat versionLocate DeepChat's package.json or version file in the installation directory and identify the installed version numberAffected if version is prior to v1.0.4-beta.1 (e.g., v1.0.3-beta.1, v1.0.2, etc.)
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Locate tabPresenter.tsSearch for the file tabPresenter.ts in the DeepChat source code or installation - typically found in the src or lib directoryAffected if the file exists and contains pop-up window handler code
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Verify vulnerable code patternInspect tabPresenter.ts for code that handles pop-up windows and calls shell.openExternal() without calling isValidExternalUrl firstAffected if code passes URLs from pop-up handlers directly to shell.openExternal() without validation
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Check for security bypass in Markdown handlingLook for code handling Markdown links with target="_blank" attributes that may trigger native window interceptionAffected if Markdown link handling exists that forwards URLs to shell.openExternal without the isValidExternalUrl check from preload/index.ts
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Confirm preload security exists but is bypassedVerify that preload/index.ts contains proper isValidExternalUrl implementation that is correctly used elsewhere but not in tabPresenter.ts pop-up handlersAffected if isValidExternalUrl exists in preload/index.ts but is NOT called by the pop-up handlers in tabPresenter.ts
You are affected if DeepChat is installed with a version prior to v1.0.4-beta.1 and the tabPresenter.ts file contains pop-up window handlers that bypass the isValidExternalUrl validation before calling shell.openExternal().
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scopedUpgrade to v1.0.4-beta.1 and ensure all code paths invoking shell.openExternal() properly validate URLs through isValidExternalUrl or equivalent sanitization before execution.
v1.0.4-beta.1
- 1. Identify all DeepChat installations in your environment and note their current version numbers
- 2. If running a version prior to v1.0.4-beta.1, plan for upgrade to v1.0.4-beta.1
- 3. Obtain v1.0.4-beta.1 from the official DeepChat repository (github.com)
- 4. Back up the current DeepChat configuration and data
- 5. Upgrade DeepChat to v1.0.4-beta.1 following standard upgrade procedures
- 6. Verify the upgrade was successful by checking the version number
- 7. Test that external URL handling works correctly and that shell.openExternal is properly validated
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation3.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-43899 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-43899 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data