Description
A critical vulnerability has been identified in the download protection mechanism of Mozilla Firefox, Firefox ESR, and Thunderbird on Windows operating systems, specifically relating to the .xrm-ms file types.
Affected Product(s)
- Mozilla Firefox < 125.0,
- Mozilla Firefox ESR < 115.10,
- Mozilla Thunderbird < 115.10.
Technical Details
Mozilla Firefox and Thunderbird are popular, widely-used open-source applications known for their security and privacy-oriented features. These applications are critical to millions of users, including those in both personal and enterprise environments. The recently discovered vulnerability, CVE-2024-3863, stems from insufficient UI warning mechanisms when users download potentially dangerous .xrm-ms files on Windows operating systems. The .xrm-ms file type is typically associated with materials related to Windows administrative and configuration management, often used in enterprise environments.
Recognizing the risks these files could carry, browsers usually present an executable warning when such files are downloaded. Unfortunately, this security mechanism was bypassed in affected versions of Firefox, Firefox ESR, and Thunderbird, increasing the risk of accidental execution of potentially malicious files. The vulnerability was classified as critical, with a CVSS v3 score of 9.8, reflecting the high potential for exploitation. The CVSS v2 severity is recorded as Medium with a score of 4.4, indicating a significant but less severe impact under older scoring criteria.
The issue was first identified under Bugzilla ID 1885855, where the specific circumstances allowing for bypass were discovered and analyzed. The analysis revealed that the bypass could happen because the browser’s warning mechanism did not properly detect the .xrm-ms files, thus presenting no security alert when users initiated downloads of these files.
The risk of exploitation is notably high because attackers could use this vulnerability to trick users into downloading and executing malicious .xrm-ms files, potentially gaining unauthorized access to systems or causing other forms of damage. The combination of insufficient UI warnings and the potentially severe impact of executing malicious .xrm-ms files creates a window of opportunity for threat actors to exploit user trust and system vulnerabilities. Mozilla quickly addressed this issue through various advisories and updates. Notably, Firefox 125, Firefox ESR 115.10, and Thunderbird 115.10 versions include patches to prevent such exploitations.
The updates ensure that users encounter appropriate warnings when attempting to download these file types, reducing the risk of accidentally running harmful executables. This vulnerability highlights the ongoing need for vigilance in software maintenance and user awareness in handling downloads, especially from untrusted sources. Given the wide deployment of these browsers and email clients, the prompt response and resolution by Mozilla significantly mitigated what could have been a widespread security incident.
In summary, CVE-2024-3863 represents a critical issue stemming from inadequate download protections for .xrm-ms files in specific versions of Mozilla products. The swift identification and patching of this vulnerability underscore the importance of continuous security evaluations and quick responses to potential threats. Users are strongly encouraged to update their software to the latest versions to ensure all security measures are in place.
Weakness
The associated weakness with this vulnerability is categorized as “Insufficient UI Warning of Dangerous Operations.” Specifically, the browser’s failure to provide an adequate security warning when users attempted to download .xrm-ms files, which are inherently risky and often linked to potentially dangerous operations.
Impact Assessment
If exploited, this vulnerability could allow an attacker to trick users into downloading and executing malicious .xrm-ms files without the users being aware of the potential risk. This exploit could lead to unauthorized access to sensitive data, system compromise, or execution of arbitrary code on the affected Windows system.
Active Exploitation
No specific adversary groups have been observed actively exploiting this vulnerability. However, the nature of the vulnerability makes it a high-priority target for attackers, particularly those interested in deploying malware via social engineering techniques.
Ransomware Association
There is no direct link between this vulnerability and specific ransomware attacks. However, the ability to download and execute unverified .xrm-ms files without warning significantly increases the risk of ransomware being deployed via this vector.
Mitigation and Resolution
Mozilla has released patches to address this vulnerability. Users of Firefox, Firefox ESR, and Thunderbird should update to versions 125.0, 115.10, and 115.10, respectively. These updates include the necessary fixes to ensure that executable warnings are appropriately presented when users attempt to download .xrm-ms files.
Recommendations
- We strongly recommend that all customers apply the latest patch as soon as possible.
- Specifically, update to Firefox version 125.0, Firefox ESR 115.10, or Thunderbird 115.10.
- Review and update security policies to ensure all software is kept up-to-date.
- Monitor download activities and educate users about the risks associated with downloading and executing files from untrusted sources.
- Implement additional security measures such as antivirus and endpoint protection to detect and prevent malicious file executions.
Referencesย
- CERT HK Security Bulletin 1
- CERT HK Security Bulletin 2
- Debian Security Tracker
- CVE MITRE Details
- Mozilla Security Advisory 1
- Mozilla Security Advisory 2
- Mozilla Security Advisory 3
- RedHat Security Advisory
- NVD Database
- Bugzilla Advisory