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

published 2026-10-30 9 d ago modified 2026-11-02 6 d ago also EUVD-2026-114461

cvss: 7.5; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.3%; EPSS 0.3% chance of exploitation in 30 days, percentile 27%
public exploits: 0; none known

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.

Patch / fix

links 1

github.com/ring-clojure/ring@18738cb commit

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-62864 updated 2026-11-02 cvss 7.5

ring/ring-core: Ring: Denial of Service via regular expression backtracking in wrap-nested-params

Red Hat Satellite 6 openvox-server 8.17.0-1.el9sat
not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation: none
Automatable: yes
Technical impact: partial
Assessed: 6 d ago (2026-11-02)

Exploit prediction

0.34% chance of exploitation in the next 30 days, higher than 27% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

ring-clojure ring

Classification

Weakness

CWE-1333 Inefficient Regular Expression Complexity

References

Sources

CVE List CVE-2026-62864
NVD CVE-2026-62864

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary