How severe is CVE-2026-41161?

No CVSS score has been assigned to CVE-2026-41161 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-41161?

CVE-2026-41161 affects the following packages: @sync-in/server (npm). Ecosystems affected: npm.

How do I fix CVE-2026-41161?

Update @sync-in/server to 2.2.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-41161 is resolved across your whole dependency graph.

How do I detect CVE-2026-41161 in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @sync-in/server, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-41161 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2026-41161 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-41161 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-41161?

CVE-2026-41161 has an EPSS (Exploit Prediction Scoring System) score of 0.3%, placing it in the 27th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-41161?

CVE-2026-41161 is classified as CWE-208 (CWE-208). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-41161 published, and has it been updated?

CVE-2026-41161 was published on May 8, 2026 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦 npm

Not in CISA KEV

CVE-2026-41161 — @sync-in/server

CVE-2026-41161 is a CWE-208 vulnerability in @sync-in/server. A fix is available for @sync-in/server — see the affected versions and patch details below.

Username Enumeration via Timing Attack

Also known asGHSA-43fj-qp3h-hrh5

Published

May 8, 2026

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

Proof-of-concept exploit code exists

CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-41161.

EPSS Exploitation Probability

via FIRST.org ↗

0.3%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs27th percentile — riskier than 27% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

0other npm packages depend on this — each one inherits the vulnerability until it's patched upstream

@sync-in/servernpm

2Kdownloads / week

Description

Summary

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. <img width="1302" height="284" alt="image" src="https://github.com/user-attachments/assets/31eeb72a-c3c2-4057-ac69-c0c92f0bbd4e" />

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 Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`@sync-in/server`	all versions	2.2.0`npm install @sync-in/server@2.2.0`

Affected Products

1 product · 1 configurations

Application

sync-in serversync-in

< 2.2.0

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @sync-in/server, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update @sync-in/server to 2.2.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-41161 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

### Summary 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 b

O3 Security · Impact-Aware SCA

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