# tinfoil-factory netfoil domain name filter bypass via multiple questions

Source: https://junglewise.ai/threats/tinfoil-factory-netfoil-domain-name-filter-bypass-via-multiple-72d002ff  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-07. Updated: 2026-07-07  
License: CC BY 4.0 with a link back

Severity: medium · CVSS 5.9 · Published 2026-07-07

netfoil is a Go-based library used for handling network traffic and DNS filtering. A security flaw allows a local attacker to bypass domain name filters by including multiple questions in a single DNS request. This could allow unauthorized access to restricted websites or services that the software was intended to block.

Technologies: [github.com/tinfoil-factory/netfoil (Go)](https://junglewise.ai/threats/technologies/github-com-tinfoil-factory-netfoil), [Tinfoil Factory Netfoil](https://junglewise.ai/threats/technologies/netfoil). Vendors: [Go](https://junglewise.ai/threats/vendors/go), [Tinfoil Factory](https://junglewise.ai/threats/vendors/tinfoil-factory).

## Quick answers

**Is This vulnerability exploited in the wild?** No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.

**How severe is This vulnerability?** Medium severity, with a CVSS score of 5.9, published 7 July 2026.

**Which products and versions are affected?** github.com/tinfoil-factory/netfoil (Go) < 0.3.0; Tinfoil Factory Netfoil < 0.3.0.

**Is there a fix for This vulnerability?** A patch was published on 0.3.0. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is This vulnerability attacked?** It is attacked with local access, in a software library.

**Am I affected?** Check whether you run github.com/tinfoil-factory/netfoil (Go) or Tinfoil Factory Netfoil at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A vulnerability exists in netfoil versions prior to 0.3.0 where the domain name filter can be bypassed due to an interpretation conflict (CWE-436). When a DNS request contains multiple questions, the filter may only validate the first (legitimate) question while allowing subsequent restricted domains to pass through to a remote DNS-over-HTTPS (DoH) server. This requires a local attacker to be able to craft multi-question DNS packets and for the upstream DoH server to support such requests. The issue is resolved in version 0.3.0.

## Affected products

- tinfoil-factory netfoil < 0.3.0

## Timeline

- 2026-05-31: disclosed
- 2026-07-07: advisory
- 0.3.0: patched

## References

- [https://github.com/tinfoil-factory/netfoil/security/advisories/GHSA-59qp-cfj3-rp64](https://github.com/tinfoil-factory/netfoil/security/advisories/GHSA-59qp-cfj3-rp64)
- [https://api.github.com/repos/tinfoil-factory/netfoil/security-advisories/GHSA-59qp-cfj3-rp64](https://api.github.com/repos/tinfoil-factory/netfoil/security-advisories/GHSA-59qp-cfj3-rp64)

## Related threats

- [Netfoil TTL not decremented in DNS responses](https://junglewise.ai/threats/go-2026-6906-netfoil-doesn-t-decrement-ttl-in-github-com-tinfoil-a5094761)
- [Netfoil TTL decrement logic flaw](https://junglewise.ai/threats/netfoil-doesn-t-decrement-ttl-f0272cfd)
- [GO-2026-6277 - netfoil vulnerable to improper handling of untrusted DoH response data in github.com/tinfoil-factory/netfoil](https://junglewise.ai/threats/go-2026-6277-netfoil-vulnerable-to-improper-handling-of-untrusted-doh-3c188b0a)
- [netfoil improper output neutralization for logs in DoH response handling](https://junglewise.ai/threats/netfoil-improper-output-neutralization-for-logs-in-doh-response-c6a8161c)
- [GO-2026-6143 - netfoil: Incorrect block responses could lead to localhost traffic in github.com/tinfoil-factory/netfoil](https://junglewise.ai/threats/go-2026-6143-netfoil-incorrect-block-responses-could-lead-to-localhost-10a9eea0)