Description

Out-of-bounds Write vulnerability in Apache HTTP Server's mod_charset_lite. This issue affects Apache HTTP Server: from 2.4.0 through 2.4.68.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "7.5",
  "pubDate": "2026-10-01T17:17:26.487Z",
  "pubdate": "2026-10-01T17:17:26.487Z",
  "executiveSummary": "A critical out-of-bounds write vulnerability has been identified in the mod_charset_lite module of the Apache HTTP Server. This memory corruption flaw allows a remote attacker to potentially cause a process crash or execute arbitrary code by supplying crafted inputs during character set translation processes.\nThe vulnerability resides within the module responsible for handling character set transcoding. If exploited, an attacker could trigger a heap-based buffer overflow, leading to unpredictable system behavior or unauthorized memory modification.\nThe affected product is Apache HTTP Server, specifically versions ranging from 2.4.0 through 2.4.68. This issue represents a significant security risk, as the affected component processes incoming requests, making it accessible to unauthorized remote actors.\nSuccessful exploitation requires the mod_charset_lite module to be enabled and configured within the server environment. The impact ranges from potential denial-of-service (DoS) via process termination to the theoretical execution of malicious code, depending on the memory layout and the attacker's ability to control the overflow payload. Organizations utilizing vulnerable versions of Apache HTTP Server are advised to assess their configuration and prepare for updates.",
  "technicalDetails": "The vulnerability is localized within the mod_charset_lite module, a component designed to provide character set translation for transmitted content. The root cause pertains to an improper bounds check during the manipulation of character conversion buffers. Specifically, when the module processes incoming data streams for transcoding, it fails to adequately validate the input length against the allocated destination buffer size.\nThe attack flow initiates when an attacker sends a specially crafted request to an Apache HTTP Server instance where mod_charset_lite is active. By manipulating the translation request parameters—such as the character set encoding headers—the attacker forces the module to perform copy operations that exceed the boundaries of the designated heap memory buffer.\nAs the module attempts to perform the translation, the out-of-bounds write occurs because the length check logic does not account for specific edge cases in multi-byte character sequences or malformed input lengths. This allows data to be written into adjacent memory addresses currently held by the heap allocator.\nExploitation involves precise heap grooming to place sensitive objects or function pointers in the path of the overflow. By corrupting adjacent control structures or metadata, an attacker can influence the program's execution flow. In a typical scenario, this could lead to the overwriting of return addresses or function pointers, allowing for control-flow hijacking.\nThe vulnerability affects Apache HTTP Server versions 2.4.0 through 2.4.68. The attack is network-exposed, meaning no local system access or specialized user interaction is required if the module is enabled on the server. The process performing the translation, typically the worker process, operates with the privileges assigned to the Apache service user.\nPost-exploitation impact is severe. An attacker could achieve a crash of the worker process, resulting in a denial-of-service condition. More sophisticated exploitation might lead to remote code execution (RCE) within the context of the Apache user. Because the vulnerability involves memory corruption, the stability of the entire server process becomes compromised once the memory heap is corrupted, leading to non-deterministic behavior that can be leveraged to bypass traditional security controls like ASLR if the attacker can identify memory offsets during a probing phase."
}