# CVE-2026-126350: Addressable: Regular Expression Denial of Service in Addressable templates with certain exploded expressions

> Attacker-controlled URIs with certain exploded template expressions cause catastrophic regex backtracking in Addressable, denying service to Ruby apps using it.

- **Severity:** Medium 5.9 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Harmful if only installed:** No
- **Needs a specific call:** Yes (`Template#match`, `Template#extract`, `Template#expand`)
- **Fix available:** Yes
- **Published:** 12 Nov 2026
- **Updated:** 12 Nov 2026
- **Also known as:** GHSA-j82w-28jv-3pmj

## What is CVE-2026-126350?

CVE-2026-126350 is a medium-severity denial of service vulnerability in sporkmonger addressable, published on 12 Nov 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Addressable is an alternative implementation to the URI implementation that is part of Ruby's standard library. From 2.3.0 until 2.9.1, URI template expressions using the explode modifier with the slash, dot, semicolon, question-mark, or ampersand operators generate ambiguous regular expressions. When Template#match or Template#extract processes an attacker-controlled URI beginning with the operator's leading character, optional member separators allow catastrophic backtracking and denial of service on MRI Ruby before 3.2 and JRuby. Addressable 2.9.0 incompletely remediated the earlier template issue because its tests did not reach these operator-prefixed paths. URI parsing and Template#expand are unaffected. This issue is fixed in version 2.9.1.

Weakness: CWE-1333 (Inefficient Regular Expression Complexity)

## Which versions are affected by CVE-2026-126350?

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

An affected version is only exploitable if your software calls Template#match, Template#extract or Template#expand. Many projects that include it are not exposed.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `addressable` | RubyGems | From 2.3.0 | 2.9.1 |

## How do I fix CVE-2026-126350?

Upgrade addressable to 2.9.1 or later.

## Is CVE-2026-126350 being exploited?

There is no known exploitation of CVE-2026-126350 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-126350 and fix it if it is affected.

What it is: CVE-2026-126350 is a medium-severity denial of service vulnerability in sporkmonger addressable, published on 12 Nov 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-126350 in the wild and no public exploit code.
Exposure: An affected version is only exploitable if your software calls Template#match, Template#extract or Template#expand. Many projects that include it are not exposed.

Affected packages and fixed versions:
- addressable (RubyGems): affected from 2.3.0; 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 Template#match, Template#extract or Template#expand 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-2026-126350/ (Markdown: https://insights.sbomify.com/CVE-2026-126350/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-126350
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-126350
- OSV: https://osv.dev/vulnerability/CVE-2026-126350

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-126350/
Summaries are generated and may contain mistakes; the official description above is the record.