# CVE-2026-126348: Addressable punycode decoding host spoofing

Source: https://junglewise.ai/threats/cve-2026-126348-addressable-is-an-alternative-implementation-to-the-uri  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-12. Updated: 2026-11-12  
License: CC BY 4.0 with a link back

CVE-2026-126348 · Severity: medium · CVSS 4.3 · Published 2026-11-12

Addressable is a Ruby library for parsing and manipulating URLs. The library's punycode decoder (used to convert internationalized domain names) incorrectly processes invalid domain labels, potentially allowing an attacker to craft a URL that displays a trusted hostname while actually connecting to an attacker-controlled server. This could enable phishing, man-in-the-middle attacks, or bypassing host-based access controls.

Technologies: [Addressable](https://junglewise.ai/threats/technologies/addressable-addressable), [addressable (RubyGems)](https://junglewise.ai/threats/technologies/addressable). Vendors: [Addressable](https://junglewise.ai/threats/vendors/addressable), [RubyGems](https://junglewise.ai/threats/vendors/rubygems).

## Quick answers

**Is CVE-2026-126348 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-126348 being exploited in the wild.

**How severe is CVE-2026-126348?** Medium severity, with a CVSS score of 4.3, published 12 November 2026.

**Which products and versions are affected?** Addressable 2.0.0 to 2.9.0; addressable (RubyGems) >= 2.0.0, < 2.9.1.

**Is there a fix for CVE-2026-126348?** Yes: fixed in 2.9.1. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-126348 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-126348?** Check whether you run Addressable or addressable (RubyGems) 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.

## How to fix

- Fixed in 2.9.1

## Technical details

The pure-Ruby implementation of Addressable::IDNA.to_unicode decodes invalid Punycode A-labels instead of rejecting them, causing labels that decode to ASCII text or fail round-trip conversion to be displayed differently from their actual connection target. An attacker can craft Punycode labels (e.g., xn--google-) that decode to trusted-looking ASCII hostnames while retaining the encoded attacker-controlled host for the actual connection. The native libidn backend and other methods are unaffected; the vulnerability requires code to rely on the pure-Ruby backend and trust display_uri output for host validation.

## Affected products

- Addressable Addressable 2.0.0 to 2.9.0

## Identifiers

- CVE-2026-126348
- GHSA-9crm-g4mf-wc5j

## Timeline

- 2026-11-12: advisory

## References

- [https://github.com/sporkmonger/addressable/commit/b8a59cc0e03f8704f1d7c8122fc8f7ef8548362d](https://github.com/sporkmonger/addressable/commit/b8a59cc0e03f8704f1d7c8122fc8f7ef8548362d)
- [https://github.com/sporkmonger/addressable/releases/tag/addressable-2.9.1](https://github.com/sporkmonger/addressable/releases/tag/addressable-2.9.1)

## Related threats

- [Addressable URI.normalize_path path traversal and bypass](https://junglewise.ai/threats/cve-2026-126354-addressable-uri-normalization-resolves-some-dotted-path-segments)
- [Addressable URI template ReDoS denial of service](https://junglewise.ai/threats/cve-2026-126352-addressable-is-an-alternative-implementation-to-the-uri)
- [Addressable URI path normalization denial of service](https://junglewise.ai/threats/cve-2026-126351-addressable-is-an-alternative-implementation-to-the-uri)
- [Addressable regular expression denial of service in URI template matching](https://junglewise.ai/threats/cve-2026-126350-addressable-is-an-alternative-implementation-to-the-uri)
- [Addressable display_uri can show misleading hosts containing bidi and invisible characters](https://junglewise.ai/threats/cve-2026-126349-addressable-is-an-alternative-implementation-to-the-uri)