CVE-2026-42934
Description
A flaw was found in the ngx_http_charset_module module of NGINX. When charset, source_charset, charset_map and proxy_pass with disabled buffering ("off") directives are configured, an unauthenticated attacker can send crafted requests and cause a heap-based buffer over-read in the worker process, resulting in a limited disclosure of memory or a denial of service by forcing the process to restart.
Statement
To exploit this vulnerability, the charset, source_charset, charset_map and proxy_pass directives must be configured with disabled buffering, limiting its exposure as this is not the default configuration. Also, configurations that do not recode a UTF-8 response through charset_map are not vulnerable. This issue allows an attacker to have limited control to disclose memory content from the worker process or cause a denial of service by forcing the process to restart, but it cannot cause a complete system denial of service. Due to these reasons, this flaw has been rated with a moderate severity.
Mitigation
To mitigate this vulnerability, enable proxy buffering (the default configuration).
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 | 4.8 | N/A | 4.8 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | High | N/A | High |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | Low | N/A | Low |
| Integrity Impact | None | N/A | None |
| Availability Impact | Low | N/A | Low |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:L
cve.org: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:L
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Memory
Confidentiality
Technical Impact: Bypass Protection Mechanism
By reading out-of-bounds memory, an attacker might be able to get secret values, such as memory addresses, which can bypass protection mechanisms such as ASLR in order to improve the reliability and likelihood of exploiting a separate weakness to achieve code execution instead of just denial of service.
Availability,Integrity
Technical Impact: DoS: Crash, Exit, or Restart
An attacker might be able to cause a crash or other denial of service by causing the product to read a memory location that is not allowed (such as a segmentation fault), or to cause other conditions in which the read operation returns more data than is expected.
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