What’s Vulnerable › Vulnerabilities

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

• Severity: low (CVSS 3.7 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-04-07 · updated 2026-10-26
• Weakness: CWE-208

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.

Affected products

• parse-community parse-server: before 8.6.74; from 9.0.0 before 9.8.0; 9.8.0-alpha1, 9.8.0-alpha2, 9.8.0-alpha3, 9.8.0-alpha4, 9.8.0-alpha5 — fixed in 8.6.74, 9.8.0

How to fix

Upgrade to a fixed version: parse-community parse-server 8.6.74, 9.8.0. Check the vendor advisory for mitigations.

References

• https://github.com/parse-community/parse-server/pull/10398
• https://github.com/parse-community/parse-server/pull/10399
• https://github.com/parse-community/parse-server/security/advisories/GHSA-mmpq-5hcv-hf2v

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