[Eclipse Theia] Data Exfiltration via Markdown Image Rendering in AI Chat

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

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

EPSS

• CVE-2026-22551: 0.31% estimated exploitation activity in the next 30 days; percentile 24.17 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

In Eclipse Theia versions prior to 1.71.0, the AI chat rendered Markdown image tags from AI responses, triggering HTTP requests to arbitrary external URLs without restriction. Combined with prompt injection in a malicious workspace, an attacker could induce the AI agent to construct image URLs encoding sensitive information from the workspace or conversation context, exfiltrating it to attacker-controlled servers. The workspace trust enforcement introduced in v1.71.0 mitigates the documented attack chain by disabling AI features in untrusted workspaces.

Published by the source

18 Jun 2026, 18:35 UTC

Last modified by the source

10 Sep 2026, 03:50 UTC

Source last checked

26 Oct 2026, 12:56 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-qwjm-9c66-w4q4

2. Revision 2 · amended · 25 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-qwjm-9c66-w4q4

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# Patch Next advisory brief: CVE-2026-22551

Advisory: [Eclipse Theia] Data Exfiltration via Markdown Image Rendering in AI Chat
IDs: CVE-2026-22551, GHSA-qwjm-9c66-w4q4
Record: https://patchnext.com/advisories/cve-2026-22551 (revision 3, source checked 26 Oct 2026, 12:56 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: @theia/ai-code-completion 1.71.0; @theia/ai-claude-code 1.71.0; @theia/ai-chat-ui 1.71.0; @theia/ai-core 1.71.0; @theia/ai-editor 1.71.0; @theia/ai-chat 1.71.0; @theia/ai-ide 1.71.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @theia/ai-code-completion: affected < 1.71.0; fixed in 1.71.0
- npm @theia/ai-claude-code: affected < 1.71.0; fixed in 1.71.0
- npm @theia/ai-chat-ui: affected < 1.71.0; fixed in 1.71.0
- npm @theia/ai-core: affected < 1.71.0; fixed in 1.71.0
- npm @theia/ai-editor: affected < 1.71.0; fixed in 1.71.0
- npm @theia/ai-chat: affected < 1.71.0; fixed in 1.71.0
- npm @theia/ai-ide: affected < 1.71.0; fixed in 1.71.0

## Suggested inspection (read-only)
- `npm ls @theia/ai-code-completion --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.
- `npm ls @theia/ai-claude-code --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.
- `npm ls @theia/ai-chat-ui --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.
- `npm ls @theia/ai-core --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.
- `npm ls @theia/ai-editor --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.
- `npm ls @theia/ai-chat --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.
- `npm ls @theia/ai-ide --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on @theia/ai-code-completion, @theia/ai-claude-code, @theia/ai-chat-ui, @theia/ai-core, @theia/ai-editor, @theia/ai-chat, @theia/ai-ide.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-qwjm-9c66-w4q4 (OSV record GHSA-qwjm-9c66-w4q4 lists affected ranges: npm @theia/ai-chat-ui >=0 =0 =0 =0 =0 =0 =0 <1.71.0 (fixed))
- Verified: https://github.com/advisories/GHSA-qwjm-9c66-w4q4 (GitHub-reviewed advisory GHSA-qwjm-9c66-w4q4 lists affected ranges: npm @theia/ai-chat-ui >=0 =0 =0 =0 =0 =0 =0 <1.71.0)

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