CVE-2026-52761
Description
A flaw was found in ModSecurity, an open-source web application firewall (WAF). The t:utf8toUnicode transformation function, responsible for converting UTF-8 encoded characters to Unicode, generates incorrect output on i386 architectures. This vulnerability allows an attacker to bypass WAF rules, potentially enabling malicious requests to reach the protected application. The consequence is a moderate integrity loss due to the circumvention of security controls.
Statement
Conditions for Exploitation: Exploitation is strictly limited to 32-bit (i386) architectures, which reduces the likelihood of exploitation in typical deployments. Furthermore, it requires the ModSecurity configuration to actively use rules that rely on the affected transformation function.
Impact Limitations: The vulnerability functions solely as a WAF rule bypass and does not directly cause privilege escalation, data corruption, or arbitrary code execution on the host system. The actual impact depends entirely on whether the backend application being protected is vulnerable to the bypassed requests.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.8 | 5.3 | 5.8 |
| Attack Vector | Network | Network | Network |
| Attack Complexity | Low | Low | Low |
| Privileges Required | None | None | None |
| User Interaction | None | None | None |
| Scope | Changed | Unchanged | Changed |
| Confidentiality | None | None | None |
| Integrity Impact | Low | Low | Low |
| Availability Impact | None | None | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N
NVD: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N
Understanding the Weakness (CWE)
Integrity,Availability,Confidentiality
Technical Impact: DoS: Crash, Exit, or Restart; Execute Unauthorized Code or Commands; Read Memory; Modify Memory
If the incorrect calculation is used in the context of memory allocation, then the software may create a buffer that is smaller or larger than expected. If the allocated buffer is smaller than expected, this could lead to an out-of-bounds read or write (CWE-119), possibly causing a crash, allowing arbitrary code execution, or exposing sensitive data.
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