CVE-2022-3515: Libksba Integer Overflow Vulnerability Leads to Remote Code Execution

A severe vulnerability, indexed as CVE-2022-3515, has been discovered in the Libksba library, a crucial component for working with X.509, CMS data structures, and various cryptographic tasks. In particular, the vulnerability affects an integer overflow issue within the Certificate Revocation List (CRL) parser. The vulnerability allows remote attackers to execute arbitrary code on the targeted system, potentially leading to severe consequences.

Exploit Details

The vulnerability arises from insufficient input validation and arithmetic operations within the Libksba library's CRL parsing function. By sending a specially crafted piece of data, such as a malicious S/MIME attachment, an attacker could remotely exploit the vulnerability and execute code on the compromised system. This vulnerability has a potentially wide-ranging impact, as Libksba is commonly utilized as a backend for cryptography-related tasks in various software.

Code Snippet

The problematic code resides in the function parse_crl_extensions within the file src/crl.c. The integer overflow is caused by the following lines of code:

for (offset = ; ; offset++)
    {
      if (offset >= objlen)
        break;
      buflen = objlen - offset;
      err = _ksba_ber_parse_tl (buf+offset, buflen, &aclass, &tag,
                                 &ti_cst, &ti_tag, &length, &hdrsz);

In this code section, variable offset is incremented in an infinite loop without proper boundary checks, leading to an integer overflow.

Steps to Reproduce the Vulnerability

To exploit the vulnerability, an attacker could create a malformed CRL by purposely crafting extensions with invalid data, making Libksba read memory beyond its intended range. By doing so, an attacker can manipulate the memory, introducing malicious code and executing it on the targeted system.

Impact

The impact of this vulnerability is remarkably high. Due to the widespread use of the Libksba library in many applications, exploitation of this vulnerability could lead to unauthorized access to sensitive data, disruption of services, and, in more critical cases, taking complete control over a compromised system.

Patches and Mitigations

The developers of the Libksba library have been notified of the vulnerability, and a patch is expected to be released shortly. In the meantime, users depending on software using the Libksba library are advised to remain vigilant and refrain from opening untrusted S/MIME attachments or handling unknown CRLs.

References

1. Libksba library official website: https://www.gnupg.org/related_software/libksba/index.html
2. CVE-2022-3515 details: https://nvd.nist.gov/vuln/detail/CVE-2022-3515

Conclusion

CVE-2022-3515, an integer overflow vulnerability within the Libksba library, is a serious issue that can lead to remote code execution. It is crucial for developers using the library to apply patches once available and monitor any software vulnerabilities. Users of affected applications should remain cautious when receiving unexpected or unknown S/MIME attachments or Certificate Revocation Lists. Together, these steps can help mitigate potential consequences related to this vulnerability.

Timeline

Published on: 01/12/2023 15:15:00 UTC
Last modified on: 05/18/2023 18:08:00 UTC