A recent vulnerability discovered in libming listswf .4.7 presents a potential risk for many applications and systems utilizing this library. The vulnerability has been assigned the identification number CVE-2023-36239. In this article, we will shed light on the details of this vulnerability, including the affected source code, exploit details, and relevant references to enhance your knowledge and understanding of the issue.

Details of the vulnerability

A buffer overflow vulnerability was discovered in the libming listswf .4.7. The issue exists within the parseSWF_DEFINEFONTINFO() function located in the parser.c file. By exploiting the vulnerability, a malicious user can cause the application to crash or potentially execute arbitrary code on a targeted system.

The relevant source code snippet in the parser.c file illustrates the issue

void parseSWF_DEFINEFONTINFO (FILE * f, int length)
    int id;
    int font_flags;
    int code;
    U16 code1;
    char *fontname;

    id = readUInt16 (f);
    font_flags = readUInt8 (f);
    code = readUInt8 (f);
    fontname = (char *) calloc (code + 1, sizeof (char));
    fread (fontname, 1, code, f);


As apparent from the code above, the function fails to properly validate the length of the input and relies on the unchecked value of code to allocate memory space for the fontname string. This could result in overwriting critical memory or program data, ultimately causing a buffer overflow.

Exploiting CVE-2023-36239

The exploitability of this vulnerability depends on an attacker's ability to provide a specially crafted SWF file that exploits the buffer overflow condition. Upon processing the malicious file using the listswf utility, the application may crash or execute arbitrary code under the context of the affected account. Please note, however, that exploiting this vulnerability is non-trivial and will likely require considerable skill and understanding of the affected application and environment.


As of this writing, there is no official patch available for the vulnerability. Users and developers are encouraged to monitor the official libming repository (https://github.com/libming/libming) for updates. We recommend restricting access points to the listswf utility, applying appropriate security measures such as input validation, and examining SWF files with antivirus or other security tools before processing.

Original references

The vulnerability was initially reported through a publication by the NVD (National Vulnerability Database). The original disclosure and additional information can be found through the following resources:

- CVE entry: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-36239
- NVD publication: https://nvd.nist.gov/vuln/detail/CVE-2023-36239


CVE-2023-36239 is a serious vulnerability that showcases how a buffer overflow can lead to crashes or execution of arbitrary code in applications using the libming listswf .4.7 library. It is crucial for developers and users to remain vigilant and keep track of updates and patches as they become available. Employing security best practices in all stages of development and use is essential to prevent and respond to potential exploits and threats effectively.


Published on: 06/22/2023 19:15:00 UTC
Last modified on: 06/29/2023 20:58:00 UTC