Vulnerability · Published Oct 30, 2026 · Assigned by GitHub_M

CVE-2026-62864Ring's nested-params middleware has inefficient regular expression complexity

High 7.5

In plain English

A high-severity regular-expression denial of service in ring from ring-clojure. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 27% of all known vulnerabilities).

Severity (CVSS 3.1)7.5High

Exploit odds (30 days)0.3%top 72.5% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

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 products (as reported)

Vendor	Product	Versions
ring-clojure	ring	< 1.15.5

Weakness: CWE-1333 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

https://github.com/ring-clojure/ring/security/advisories/GHSA-q2j3-fc6x-78jj x_refsource_CONFIRM
https://github.com/ring-clojure/ring/commit/18738cbb8ab7504da4a5c72c9eb5fdcbf142646e x_refsource_MISC
https://github.com/ring-clojure/ring/tree/1.15.5 x_refsource_MISC