CVE-2022-22747 - Recovering From a Potentially Unexploitable Crash in Firefox and Thunderbird After Accepting an Untrusted Certificate

The security world constantly undergoes rapid changes and challenges, and staying up-to-date with the latest vulnerabilities is necessary for better protection. One such vulnerability that has raised concerns is the CVE-2022-22747, which has affected Firefox ESR, Firefox, and Thunderbird. This post will extensively share insights on this specific vulnerability, elaborate on the potential exploit details, provide code snippets, and include links to original references.

About CVE-2022-22747

CVE-2022-22747 is a vulnerability that was discovered after accepting an untrusted certificate, where handling an empty PKCS#7 (Public Key Cryptography Standards) sequence as part of the certificate data could potentially lead to a crash. Although the crash is believed to be unexploitable, it is important to address the vulnerability. This vulnerability affects Firefox ESR < 91.5, Firefox < 96, and Thunderbird < 91.5.

Exploit Details

The crash occurs due to the improper handling of an empty PKCS#7 sequence. PKCS#7 is a widely-used standard for cryptographically protected messages. These messages may include digital signatures and enveloped data, among other things. The vulnerability stems from the incorrect implementation of the PKCS#7 parsing mechanism in the affected software. Below is a simplified code snippet that demonstrates the vulnerability:

/* Sample vulnerable code snippet */
int parse_pkcs7_message(/*arguments*/) {
  /* ... */
  while (/* some_condition */) {
    /* ... */
    if (/* is_empty_pkcs7_component */) {
      /* ... */
      return ERROR_CODE;  // Improper error handling could lead to a crash
    }
  /* ... */
  }
  /* ... */
}

As evident from the code snippet, the software may crash if an empty PKCS#7 component is encountered while parsing the content. The implementation does not correctly handle this scenario, thus causing the crash.

It is important to note that researchers believe this vulnerability is unexploitable, meaning that an attacker cannot execute arbitrary code or exfiltrate data from the system as a direct result of the crash. Nevertheless, it is essential to take preventive measures and implement the necessary fixes to protect your systems.

Original References

1. Official Mozilla CVE-2022-22747 Advisory: https://www.mozilla.org/en-US/security/advisories/mfsa2022-04/#CVE-2022-22747
2. Firefox Release Notes: https://www.mozilla.org/en-US/firefox/96./releasenotes/
3. Thunderbird Release Notes: https://www.thunderbird.net/en-US/thunderbird/91.5./releasenotes/

Mitigation

Users are advised to update their Firefox ESR, Firefox, and Thunderbird software versions to eliminate this vulnerability. The specific versions to which users should update are as follows:

Conclusion

CVE-2022-22747 is a vulnerability that, while believed to be unexploitable, could lead to an undesirable crash in certain Mozilla products. By updating the affected software to their respective latest versions, users can ensure better system protection and avoid any potential disruptions that may be caused by this vulnerability. Always keep your software up-to-date and stay informed about emerging threats for enhanced security.

Timeline

Published on: 12/22/2022 20:15:00 UTC
Last modified on: 12/29/2022 23:17:00 UTC