---
id: CVE-2026-62864
title: Ring's nested-params middleware has inefficient regular expression complexity
summary: >-
  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 …
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cvssSource: cna
cwe:
  - CWE-1333
vendor: ring-clojure
product: ring
affected:
  - ring < 1.15.5
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-11-02T15:04:29.414692Z'
published: '2026-10-30'
updated: '2026-11-02'
sourceUpdated: '2026-11-02T15:05:18.669Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-62864'
references:
  - url: >-
      https://github.com/ring-clojure/ring/security/advisories/GHSA-q2j3-fc6x-78jj
    label: >-
      https://github.com/ring-clojure/ring/security/advisories/GHSA-q2j3-fc6x-78jj
  - url: >-
      https://github.com/ring-clojure/ring/commit/18738cbb8ab7504da4a5c72c9eb5fdcbf142646e
    label: >-
      https://github.com/ring-clojure/ring/commit/18738cbb8ab7504da4a5c72c9eb5fdcbf142646e
  - url: 'https://github.com/ring-clojure/ring/tree/1.15.5'
    label: 'https://github.com/ring-clojure/ring/tree/1.15.5'
tags:
  - cve.org
epss: 0.00339
epssPercentile: 0.27483
ingestedAt: '2026-11-05T19:30:42.689Z'
---

## Overview

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.

## Affected

- `ring < 1.15.5`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.