---
id: "CVE-2026-62864"
kind: "vulnerability"
aliases: ["CVE-2026-62864"]
title: "Ring Clojure library: crafted parameter names cause regex denial of service"
severity: "high"
cvss: 7.5
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["clojure", "package", "ring", "web-apps"]
not_affected_if: ["no-nested-params-middleware", "ring-version-1.15.5-or-later"]
published_at: "2026-10-30T21:17:14+00:00"
first_seen_at: "2026-10-30T21:25:53+00:00"
updated_at: "2026-10-30T21:26:43+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-62864", "first_seen_at": "2026-10-30T21:25:53+00:00"}]
---

# Ring Clojure library: crafted parameter names cause regex denial of service

Ring is a Clojure library for web applications; before 1.15.5, its nested-params middleware uses a backtracking regular expression on request parameter names. An attacker can send a crafted parameter name that makes the server spend quadratic time matching it, causing a denial of service.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the Ring version in the project's dependency file (for example `project.clj` or `deps.edn`) and confirm whether it is below `1.15.5`.
- Search the code for `wrap-nested-params` or `ring.middleware.nested-params`, including use through `Ring-Defaults`, since nested-params is enabled by default there.

## Fix

- Ring: upgrade to `1.15.5`

## Timeline

- 2026-10-30T21:25:53+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-62864

## From the sources

Ring is a Clojure web applications library inspired by Python's WSGI and Ruby's Rack. Prior to 1.15.5, `wrap-nested-params` in the `ring.middleware.nested-params` namespace uses a backtracking regular expression to match parameter names from URL query strings and HTTP request bodies. An attacker can craft a parameter name that drives quadratic O(n^2) matching work, causing regular-expression denial of service in applications using the middleware. `Ring-Defaults` users are also exposed because nested-params is enabled by default. Applications omitting the middleware do not expose this parsing path. This issue is fixed in version 1.15.5.

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