CVE-2026-39321

Description

### Impact The 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. ### Patches A dummy bcrypt comparison is now performed when no user is found, normalizing response timing regardless of user existence. Additionally, accounts without a stored password (e.g. OAuth-only) now also run a dummy comparison to prevent the same timing oracle. ### Workarounds Configure rate limiting on the login endpoint to slow automated enumeration. This reduces throughput but does not eliminate the timing signal for individual requests.

How to fix CVE-2026-39321

To remediate CVE-2026-39321, upgrade the affected package to a fixed version below.

• —upgrade to 8.6.74 or later
• —upgrade to 9.8.0-alpha.6 or later

Is CVE-2026-39321 being exploited?

Low — EPSS is 0.0%, meaning exploitation activity has not been observed at scale.

Affected packages (2)

• from 0, < 8.6.74, >= 9.0.0, < 9.8.0
• >= 9.0.0, < 9.8.0-alpha.6

CVSS scores

References (5)

• ADVISORYnvd.nist.gov/vuln/detail/CVE-2026-39321
• PATCHgithub.com/parse-community/parse-server
• WEBgithub.com/parse-community/parse-server/pull/10398
• WEBgithub.com/parse-community/parse-server/pull/10399