# CVE-2026-126348: Addressable display_uri can show misleading hosts with invalid Punycode A-labels

> Attackers can craft hosts with invalid Punycode A-labels that make Addressable show a trusted host, enabling phishing in Ruby apps relying on it.

- **Severity:** Medium 4.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Harmful if only installed:** No
- **Needs a specific call:** Yes (`Addressable::IDNA.to_unicode`, `Addressable::URI#display_uri`)
- **Fix available:** Yes
- **Published:** 12 Nov 2026
- **Updated:** 12 Nov 2026
- **Also known as:** GHSA-9crm-g4mf-wc5j

## What is CVE-2026-126348?

CVE-2026-126348 is a medium-severity security feature bypass vulnerability in sporkmonger addressable, published on 12 Nov 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

Addressable is an alternative implementation to the URI implementation that is part of Ruby's standard library. From 2.0.0 until 2.9.1, the pure-Ruby Addressable::IDNA.to_unicode implementation decodes invalid Punycode A-labels instead of returning them unchanged. Labels that decode to ASCII text or fail to convert back to the same A-label can therefore make Addressable::URI#display_uri show a trusted-looking host while host, normalized_host, and the connection target retain the attacker-controlled encoded host. A trusted-name comparison using Addressable::IDNA.to_unicode output can also treat two different hosts as the same without displaying the URI. The native libidn implementation, to_ascii, and normalized_host are unaffected. This issue is fixed in version 2.9.1.

Weakness: CWE-20 (Improper Input Validation), CWE-1007 (Insufficient Visual Distinction of Homoglyphs Presented to User)

## Which versions are affected by CVE-2026-126348?

1 open source package ship an affected version, including addressable.

An affected version is only exploitable if your software calls Addressable::IDNA.to_unicode or Addressable::URI#display_uri. Many projects that include it are not exposed.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `addressable` | RubyGems | From 2.0.0 | 2.9.1 |

## How do I fix CVE-2026-126348?

Upgrade addressable to 2.9.1 or later.

## Is CVE-2026-126348 being exploited?

There is no known exploitation of CVE-2026-126348 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-126348 and fix it if it is affected.

What it is: CVE-2026-126348 is a medium-severity security feature bypass vulnerability in sporkmonger addressable, published on 12 Nov 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-126348 in the wild and no public exploit code.
Exposure: An affected version is only exploitable if your software calls Addressable::IDNA.to_unicode or Addressable::URI#display_uri. Many projects that include it are not exposed.

Affected packages and fixed versions:
- addressable (RubyGems): affected from 2.0.0; fixed in 2.9.1

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
   If an affected version is present, also search the code for calls to Addressable::IDNA.to_unicode or Addressable::URI#display_uri and report whether any exist.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-126348/ (Markdown: https://insights.sbomify.com/CVE-2026-126348/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-126348
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-126348
- OSV: https://osv.dev/vulnerability/CVE-2026-126348

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-126348/
Summaries are generated and may contain mistakes; the official description above is the record.