Parse Server: MFA SMS one-time password accepted twice under concurrent login

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Prior to 8.6.76 and 9.9.0-alpha.2, 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 vulnerability is fixed in 8.6.76 and 9.9.0-alpha.2.

Source published

12 May 2026 13:34:50 UTC

Source modified

13 May 2026 14:27:47 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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CVSS 4.0 · 2.1 CVSS:4.0/AV:N/AC:H/AT:N/PR:H/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Prior to 8.6.76 and 9.9.0-alpha.2, 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 vulnerability is fixed in 8.6.76 and 9.9.0-alpha.2.

Source published

May 12, 2026, 1:34:50 PM (timezone not stated)

Source modified

May 13, 2026, 2:27:47 PM (timezone not stated)

Observed here

7 Nov 2026 09:37:21 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 4.0 · 2.1 CVSS:4.0/AV:N/AC:H/AT:N/PR:H/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Prior to 8.6.76 and 9.9.0-alpha.2, 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 vulnerability is fixed in 8.6.76 and 9.9.0-alpha.2.

Source published

12 May 2026 14:17:08 UTC

Source modified

26 Oct 2026 18:10:00 UTC

Observed here

27 Oct 2026 11:12:04 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 4.0 · [email protected] · Secondary · 2.1 CVSS:4.0/AV:N/AC:H/AT:N/PR:H/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

CVSS 3.1 · [email protected] · Primary · 5.9 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

### Impact 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](https://github.com/parse-community/parse-server/security/advisories/GHSA-2299-ghjr-6vjp) (TOTP recovery codes) and [GHSA-w73w-g5xw-rwhf](https://github.com/parse-community/parse-server/security/advisories/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. ### Patches 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`. ### 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

Source published

5 May 2026 20:30:44 UTC

Source modified

14 May 2026 12:26:29 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V4 · CVSS:4.0/AV:N/AC:H/AT:N/PR:H/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

Publisher rating · LOW