OWASP Modsecurity

ModSecurity <2.9.10 Denial-of-Service via sanitiseArg Argument Bombing
CVE-2025-48866 - June 02, 2025

ModSecurity is an open source, cross platform web application firewall (WAF) engine for Apache, IIS and Nginx. Versions prior to 2.9.10 contain a denial of service vulnerability similar to GHSA-859r-vvv8-rm8r/CVE-2025-47947. The `sanitiseArg` (and `sanitizeArg` - this is the same action but an alias) is vulnerable to adding an excessive number of arguments, thereby leading to denial of service. Version 2.9.10 fixes the issue. As a workaround, avoid using rules that contain the `sanitiseArg` (or `sanitizeArg`) action.

Excessive Platform Resource Consumption within a Loop

CVE-2024-46292: ModSecurity 3.0.12 DoS via name param buffer overflow
CVE-2024-46292 - October 09, 2024

A buffer overflow in modsecurity v3.0.12 allows attackers to cause a Denial of Service (DoS) via a crafted input inserted into the name parameter. NOTE: this is disputed by the Supplier because it cannot be reproduced. Also, the product's documentation indicates that it is not guaranteed to be usable with very large values of SecRequestBodyNoFilesLimit (which are required by the claimed issue).

ModSecurity 3.0.0-3.0.11 WAF Bypass via URL Path, Fixed in 3.0.12
CVE-2024-1019 8.6 - High - January 30, 2024

ModSecurity / libModSecurity 3.0.0 to 3.0.11 is affected by a WAF bypass for path-based payloads submitted via specially crafted request URLs. ModSecurity v3 decodes percent-encoded characters present in request URLs before it separates the URL path component from the optional query string component. This results in an impedance mismatch versus RFC compliant back-end applications. The vulnerability hides an attack payload in the path component of the URL from WAF rules inspecting it. A back-end may be vulnerable if it uses the path component of request URLs to construct queries. Integrators and users are advised to upgrade to 3.0.12. The ModSecurity v2 release line is not affected by this vulnerability.

Trustwave ModSecurity 3.x before 3.0.10 has Inefficient Algorithmic Complexity.
CVE-2023-38285 7.5 - High - July 26, 2023

Trustwave ModSecurity 3.x before 3.0.10 has Inefficient Algorithmic Complexity.

Inefficient Algorithmic Complexity

Trustwave ModSecurity 3.0.5 through 3.0.8 before 3.0.9
CVE-2023-28882 7.5 - High - April 28, 2023

Trustwave ModSecurity 3.0.5 through 3.0.8 before 3.0.9 allows a denial of service (worker crash and unresponsiveness) because some inputs cause a segfault in the Transaction class for some configurations.

Resource Exhaustion

In ModSecurity before 2.9.6 and 3.x before 3.0.8
CVE-2022-48279 7.5 - High - January 20, 2023

In ModSecurity before 2.9.6 and 3.x before 3.0.8, HTTP multipart requests were incorrectly parsed and could bypass the Web Application Firewall. NOTE: this is related to CVE-2022-39956 but can be considered independent changes to the ModSecurity (C language) codebase.

Interpretation Conflict

ModSecurity 3.x through 3.0.5 mishandles excessively nested JSON objects
CVE-2021-42717 7.5 - High - December 07, 2021

ModSecurity 3.x through 3.0.5 mishandles excessively nested JSON objects. Crafted JSON objects with nesting tens-of-thousands deep could result in the web server being unable to service legitimate requests. Even a moderately large (e.g., 300KB) HTTP request can occupy one of the limited NGINX worker processes for minutes and consume almost all of the available CPU on the machine. Modsecurity 2 is similarly vulnerable: the affected versions include 2.8.0 through 2.9.4.

Stack Exhaustion

ModSecurity 3.x before 3.0.4 mishandles key-value pair parsing
CVE-2019-25043 5.3 - Medium - May 06, 2021

ModSecurity 3.x before 3.0.4 mishandles key-value pair parsing, as demonstrated by a "string index out of range" error and worker-process crash for a "Cookie: =abc" header.

Improper Handling of Exceptional Conditions

Trustwave ModSecurity 3.x through 3.0.4 allows denial of service via a special request
CVE-2020-15598 7.5 - High - October 06, 2020

Trustwave ModSecurity 3.x through 3.0.4 allows denial of service via a special request. NOTE: The discoverer reports "Trustwave has signaled they are disputing our claims." The CVE suggests that there is a security issue with how ModSecurity handles regular expressions that can result in a Denial of Service condition. The vendor does not consider this as a security issue because1) there is no default configuration issue here. An attacker would need to know that a rule using a potentially problematic regular expression was in place, 2) the attacker would need to know the basic nature of the regular expression itself to exploit any resource issues. It's well known that regular expression usage can be taxing on system resources regardless of the use case. It is up to the administrator to decide on when it is appropriate to trade resources for potential security benefit

Infinite Loop

Trustwave ModSecurity 3.0.0 through 3.0.3 allows an attacker to send crafted requests
CVE-2019-19886 7.5 - High - January 21, 2020

Trustwave ModSecurity 3.0.0 through 3.0.3 allows an attacker to send crafted requests that may, when sent quickly in large volumes, lead to the server becoming slow or unresponsive (Denial of Service) because of a flaw in Transaction::addRequestHeader in transaction.cc.

Improper Resource Shutdown or Release

ModSecurity 3.0.0 has XSS via an onerror attribute of an IMG element
CVE-2018-13065 6.1 - Medium - July 03, 2018

ModSecurity 3.0.0 has XSS via an onerror attribute of an IMG element. NOTE: a third party has disputed this issue because it may only apply to environments without a Core Rule Set configured

XSS