CVE-2026-43930

Workarounds

• Disable SMS MFA and use TOTP instead (TOTP tokens are time-window validated, not stored single-use).
• Place a rate limiter on the /login endpoint to reduce concurrent-request burst capacity.

Resources

• GitHub security advisory: https://github.com/parse-community/parse-server/security/advisories/GHSA-jpq4-7fmq-q5fj
• Fix Parse Server 9: https://github.com/parse-community/parse-server/pull/10448
• Fix Parse Server 8: https://github.com/parse-community/parse-server/pull/10449

A race condition in the MFA SMS one-time password (OTP) login path allows two concurrent /login requests carrying the same OTP to both succeed and both receive valid session tokens, breaking the single-use property of the OTP. The vulnerability requires the attacker to already possess the victim's password and intercept the active SMS OTP (e.g. via SIM swap, network mirror, or phishing relay) and to race the legitimate login request, so the practical attack surface is narrow.

This advisory is the same class of incomplete fix as GHSA-2299-ghjr-6vjp (TOTP recovery codes) and GHSA-w73w-g5xw-rwhf (MFA recovery in authData-only login). Those previous fixes added optimistic locking only for array-typed authData fields; SMS MFA stores the OTP as a string, so the guard skipped it.

Multiple concurrent operations access a shared resource without proper synchronization, producing unpredictable results depending on timing. Typical impact: TOCTOU exploits, data corruption, or privilege escalation.

Kodem intelligence

The optimistic lock has been generalized to cover primitive (string, number, boolean) and array authData fields. The lock is implemented as a shared helper applyAuthDataOptimisticLock that adds equality predicates on the original values of changed fields to the update WHERE clause. Concurrent writers racing the same single-use token now miss the WHERE condition and surface as Invalid auth data.

1. What is CVE-2026-43930? CVE-2026-43930 is a low-severity race condition vulnerability in parse-server (npm), affecting versions >= 9.0.0, < 9.9.0-alpha.2. It is fixed in 9.9.0-alpha.2, 8.6.76. Multiple concurrent operations access a shared resource without proper synchronization, producing unpredictable results depending on timing.
2. Which versions of parse-server are affected by CVE-2026-43930? parse-server (npm) versions >= 9.0.0, < 9.9.0-alpha.2 is affected.
3. Is there a fix for CVE-2026-43930? Yes. CVE-2026-43930 is fixed in 9.9.0-alpha.2, 8.6.76. Upgrade to this version or later.
4. Is CVE-2026-43930 exploitable, and should I be worried? Whether CVE-2026-43930 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
5. What actually determines whether CVE-2026-43930 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
6. How do I fix CVE-2026-43930?
   • Upgrade parse-server to 9.9.0-alpha.2 or later
   • Upgrade parse-server to 8.6.76 or later