GHSA-43FJ-QP3H-HRH5
Vulnerability from github – Published: 2026-04-15 18:57 – Updated: 2026-05-12 13:31Summary
The /api/auth/login endpoint contains a logic flaw that allows unauthenticated remote attackers to enumerate valid usernames by measuring the application's response time.
Details
The logic flaw can be located at the below point in source: https://github.com/Sync-in/server/blob/7868bb2b3025f92e6c38087456304758713971b2/backend/src/applications/users/services/users-queries.service.ts#L91-L95
Endpoints used for authentication should respond to the user with a consistent cadence, preventing remote actors from deriving sensitive information about an application based on backend behavior. In the case of authentication endpoints, this timing discrepancy is often caused by short-circuiting due to the lack of a matched user to compare against - as is the case with Sync-in.
Validation
TickTock Enum (Burp Suite Extension) was utilized to validate this finding. Authentication attempts with a valid username see a response from the application at around 350-400ms on average, while invalid usernames are returned at only 95-100ms on average.
Impact
An unauthenticated remote attacker can enumerate valid usernames. This significantly weakens the application's security posture by facilitating targeted brute-force attacks, stuffing, social engineering, and a suite of other more targeted attacks.
{
"affected": [
{
"database_specific": {
"last_known_affected_version_range": "\u003c= 2.1.0"
},
"package": {
"ecosystem": "npm",
"name": "@sync-in/server"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "2.2.0"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-41161"
],
"database_specific": {
"cwe_ids": [
"CWE-208"
],
"github_reviewed": true,
"github_reviewed_at": "2026-04-15T18:57:50Z",
"nvd_published_at": "2026-05-08T14:16:33Z",
"severity": "MODERATE"
},
"details": "### Summary\nThe `/api/auth/login` endpoint contains a logic flaw that allows unauthenticated remote attackers to enumerate valid usernames by measuring the application\u0027s response time.\n\n### Details\nThe logic flaw can be located at the below point in source:\nhttps://github.com/Sync-in/server/blob/7868bb2b3025f92e6c38087456304758713971b2/backend/src/applications/users/services/users-queries.service.ts#L91-L95\n\nEndpoints used for authentication should respond to the user with a consistent cadence, preventing remote actors from deriving sensitive information about an application based on backend behavior. In the case of authentication endpoints, this timing discrepancy is often caused by short-circuiting due to the lack of a matched user to compare against - as is the case with Sync-in.\n\n### Validation\nTickTock Enum (Burp Suite Extension) was utilized to validate this finding. Authentication attempts with a valid username see a response from the application at around 350-400ms on average, while invalid usernames are returned at only 95-100ms on average.\n\u003cimg width=\"1302\" height=\"284\" alt=\"image\" src=\"https://github.com/user-attachments/assets/31eeb72a-c3c2-4057-ac69-c0c92f0bbd4e\" /\u003e\n\n### Impact\nAn unauthenticated remote attacker can enumerate valid usernames. This significantly weakens the application\u0027s security posture by facilitating targeted brute-force attacks, stuffing, social engineering, and a suite of other more targeted attacks.",
"id": "GHSA-43fj-qp3h-hrh5",
"modified": "2026-05-12T13:31:20Z",
"published": "2026-04-15T18:57:50Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/Sync-in/server/security/advisories/GHSA-43fj-qp3h-hrh5"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-41161"
},
{
"type": "PACKAGE",
"url": "https://github.com/Sync-in/server"
},
{
"type": "WEB",
"url": "https://github.com/Sync-in/server/releases/tag/v2.2.0"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N",
"type": "CVSS_V4"
}
],
"summary": "Sync-in Server has Username Enumeration via Timing Attack"
}
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
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- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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