CVE-2026-39321
LOW3.7EPSS 0.03%Parse Server has a login timing side-channel reveals user existence
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.
Affected packages (2)
- Bitnami/parsefrom 0, < 8.6.74, >= 9.0.0, < 9.8.0
- npm/parse-server>= 9.0.0, < 9.8.0-alpha.6
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 4.0 | — | 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 |
| osv | CVSS 3.1 | LOW3.7 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N |
References (5)
- ADVISORYhttps://nvd.nist.gov/vuln/detail/CVE-2026-39321
- PATCHhttps://github.com/parse-community/parse-server
- WEBhttps://github.com/parse-community/parse-server/pull/10398
- WEBhttps://github.com/parse-community/parse-server/pull/10399
- WEBhttps://github.com/parse-community/parse-server/security/advisories/GHSA-mmpq-5hcv-hf2v