CVE-2024-27928: vantage6 Auth Bypass Vulnerability

CVE-2024-27928 Overview

CVE-2024-27928 affects vantage6, an open-source infrastructure for privacy preserving analysis. Versions prior to 5.0.0 allow an attacker who compromises a user's email account to reduce two-factor authentication (2FA) to single-factor authentication. The attacker can reset the account password via email and subsequently reset the 2FA token via the same email channel. This collapses both authentication factors into a single channel: email access. The vantage6 maintainers released version 5.0.0 to address the issue, tracked under GitHub Security Advisory GHSA-4c5c-2vc3-x5w2.

Critical Impact
An attacker with control over a vantage6 user's email inbox can reset both the account password and the 2FA token, fully taking over the account without needing the original second factor.

Affected Products

vantage6 versions prior to 5.0.0
vantage6 server deployments using email-based password and 2FA reset flows
Self-hosted vantage6 instances supporting federated privacy preserving analysis

Discovery Timeline

2026-06-17 - CVE-2024-27928 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2024-27928

Vulnerability Analysis

The weakness is classified as [CWE-308] Use of Single-factor Authentication. vantage6 supports 2FA to protect user accounts, but both recovery flows for the password and the 2FA secret terminate at the same email address. An attacker who obtains access to that mailbox can chain the two reset operations to bypass the second factor entirely.

The attack sequence is:

The attacker triggers a password reset for the target vantage6 account.
The reset link arrives in the compromised inbox, allowing the attacker to set a new password.
The attacker then triggers a 2FA reset, which is also delivered via email.
After consuming both reset emails, the attacker logs in with the new password and the newly enrolled 2FA factor.

Because both factors are recoverable through the same channel, the effective authentication strength is reduced to whatever protects the email account. The vantage6 advisory notes that most email providers themselves enforce 2FA, which limits real-world exposure but does not eliminate the design weakness.

Root Cause

The root cause is an authentication design flaw rather than a memory-safety or input-validation bug. The password reset workflow and the 2FA reset workflow both rely solely on possession of the account's email address as proof of identity. No independent out-of-band verification is required before resetting the second factor.

Attack Vector

Exploitation requires prior compromise of the victim's email account, which is reflected in the high privileges required component of the score. Once that prerequisite is met, the attack is performed over the network against the vantage6 web interface using standard account recovery requests. No user interaction by the legitimate account holder is needed. See GitHub Issue #1932 for the upstream discussion.

No verified proof-of-concept code is published for this issue, so exploitation is described in prose rather than with synthetic code.

Detection Methods for CVE-2024-27928

Indicators of Compromise

Password reset and 2FA reset events for the same vantage6 user account occurring within a short window.
Successful logins from new IP addresses or geolocations immediately following paired reset events.
New 2FA enrollment entries in the vantage6 server logs that are not associated with a legitimate user request.

Detection Strategies

Correlate vantage6 application logs for sequences of password reset followed by 2FA reset for the same user_id.
Alert on any 2FA reset event that is not preceded by an authenticated session from a known device.
Monitor authentication telemetry for logins that occur immediately after a 2FA reset and originate from previously unseen sources.

Monitoring Recommendations

Forward vantage6 server and email gateway logs into a centralized analytics platform for cross-source correlation.
Track email account takeover signals for users with vantage6 access, including impossible-travel logins and inbox rule changes.
Review administrative audit logs in vantage6 for unexpected role or permission changes following account recovery actions.

How to Mitigate CVE-2024-27928

Immediate Actions Required

Upgrade all vantage6 server deployments to version 5.0.0 or later as published in the GitHub Release Notes 5.0.0.
Enforce strong, provider-side 2FA on every email account associated with a vantage6 user.
Audit recent password reset and 2FA reset events and require re-verification for any account that performed both within a short window.
Rotate API tokens and session credentials for vantage6 accounts that show suspicious recovery activity.

Patch Information

The vantage6 maintainers fixed the issue in version 5.0.0. Administrators should consult the upstream GitHub Security Advisory GHSA-4c5c-2vc3-x5w2 for upgrade guidance and verify the running server version after deployment.

Workarounds

No workarounds are available according to the vendor advisory; upgrading to version 5.0.0 is the only supported fix.
As a compensating control, require email accounts used with vantage6 to enforce phishing-resistant 2FA such as hardware security keys.
Restrict vantage6 administrative access to a small set of accounts with hardened email security until the upgrade is complete.

bash

# Configuration example: verify the installed vantage6 version meets the fixed release
pip show vantage6 | grep -i version
pip install --upgrade "vantage6>=5.0.0"