CVE-2023-32206: Crash in RLBox Expat driver in Mozilla Firefox
An out-of-bound read could have led to a crash in the RLBox Expat driver. This vulnerability affects Firefox < 113, Firefox ESR < 102.11, and Thunderbird < 102.11.
AI Analysis
Technical Summary
CVE-2023-32206 is a vulnerability identified in the RLBox Expat driver component used by Mozilla Firefox and Thunderbird. The issue is an out-of-bound read that can cause the affected applications to crash. Specifically, this vulnerability affects Firefox versions prior to 113, Firefox ESR (Extended Support Release) versions prior to 102.11, and Thunderbird versions prior to 102.11. The RLBox framework is a sandboxing technology used by Mozilla to isolate third-party libraries, such as Expat, which is an XML parser. An out-of-bound read occurs when the software reads data beyond the allocated memory buffer, which can lead to application instability or crashes. While this vulnerability does not appear to allow arbitrary code execution or privilege escalation, the resulting crash can cause denial of service (DoS) conditions. No known exploits are currently reported in the wild, and no CVSS score has been assigned yet. The vulnerability was publicly disclosed on June 2, 2023, with Mozilla as the assigner. Given the nature of the bug, it is primarily a stability and availability concern rather than a direct confidentiality or integrity threat. However, crashes in browsers or email clients can disrupt user workflows and potentially be leveraged in more complex attack chains if combined with other vulnerabilities.
Potential Impact
For European organizations, this vulnerability could lead to service disruptions if Firefox or Thunderbird clients crash unexpectedly. Organizations relying heavily on Firefox for web access or Thunderbird for email communications may experience reduced productivity or interruptions. In environments where these applications are used in critical workflows, such as government agencies, financial institutions, or healthcare providers, even temporary denial of service can have operational impacts. While this vulnerability does not directly expose sensitive data or allow remote code execution, the instability could be exploited by attackers to cause targeted disruptions or as part of multi-stage attacks. Additionally, organizations with strict uptime requirements or regulatory obligations for service availability may face compliance challenges if crashes occur frequently. The lack of known exploits reduces immediate risk, but the widespread use of Firefox and Thunderbird in Europe means that unpatched systems remain vulnerable to potential future exploitation or accidental crashes triggered by malformed XML content.
Mitigation Recommendations
Organizations should prioritize updating affected Mozilla products to the latest versions: Firefox 113 or later, Firefox ESR 102.11 or later, and Thunderbird 102.11 or later. Applying these updates will address the out-of-bound read vulnerability in the RLBox Expat driver. Beyond patching, organizations can implement input validation and filtering at network boundaries to block or sanitize potentially malicious XML content that could trigger the crash. Security teams should monitor application logs and user reports for signs of unexpected crashes that might indicate exploitation attempts or malformed content delivery. Deploying endpoint protection solutions that detect abnormal application behavior can help identify exploitation attempts early. For high-security environments, consider restricting the use of vulnerable versions of Firefox and Thunderbird until patches are applied. Finally, maintain regular vulnerability scanning and asset inventory to ensure all instances of these applications are identified and updated promptly.
Affected Countries
Germany, France, United Kingdom, Italy, Spain, Netherlands, Poland, Sweden, Belgium, Austria
CVE-2023-32206: Crash in RLBox Expat driver in Mozilla Firefox
Description
An out-of-bound read could have led to a crash in the RLBox Expat driver. This vulnerability affects Firefox < 113, Firefox ESR < 102.11, and Thunderbird < 102.11.
AI-Powered Analysis
Technical Analysis
CVE-2023-32206 is a vulnerability identified in the RLBox Expat driver component used by Mozilla Firefox and Thunderbird. The issue is an out-of-bound read that can cause the affected applications to crash. Specifically, this vulnerability affects Firefox versions prior to 113, Firefox ESR (Extended Support Release) versions prior to 102.11, and Thunderbird versions prior to 102.11. The RLBox framework is a sandboxing technology used by Mozilla to isolate third-party libraries, such as Expat, which is an XML parser. An out-of-bound read occurs when the software reads data beyond the allocated memory buffer, which can lead to application instability or crashes. While this vulnerability does not appear to allow arbitrary code execution or privilege escalation, the resulting crash can cause denial of service (DoS) conditions. No known exploits are currently reported in the wild, and no CVSS score has been assigned yet. The vulnerability was publicly disclosed on June 2, 2023, with Mozilla as the assigner. Given the nature of the bug, it is primarily a stability and availability concern rather than a direct confidentiality or integrity threat. However, crashes in browsers or email clients can disrupt user workflows and potentially be leveraged in more complex attack chains if combined with other vulnerabilities.
Potential Impact
For European organizations, this vulnerability could lead to service disruptions if Firefox or Thunderbird clients crash unexpectedly. Organizations relying heavily on Firefox for web access or Thunderbird for email communications may experience reduced productivity or interruptions. In environments where these applications are used in critical workflows, such as government agencies, financial institutions, or healthcare providers, even temporary denial of service can have operational impacts. While this vulnerability does not directly expose sensitive data or allow remote code execution, the instability could be exploited by attackers to cause targeted disruptions or as part of multi-stage attacks. Additionally, organizations with strict uptime requirements or regulatory obligations for service availability may face compliance challenges if crashes occur frequently. The lack of known exploits reduces immediate risk, but the widespread use of Firefox and Thunderbird in Europe means that unpatched systems remain vulnerable to potential future exploitation or accidental crashes triggered by malformed XML content.
Mitigation Recommendations
Organizations should prioritize updating affected Mozilla products to the latest versions: Firefox 113 or later, Firefox ESR 102.11 or later, and Thunderbird 102.11 or later. Applying these updates will address the out-of-bound read vulnerability in the RLBox Expat driver. Beyond patching, organizations can implement input validation and filtering at network boundaries to block or sanitize potentially malicious XML content that could trigger the crash. Security teams should monitor application logs and user reports for signs of unexpected crashes that might indicate exploitation attempts or malformed content delivery. Deploying endpoint protection solutions that detect abnormal application behavior can help identify exploitation attempts early. For high-security environments, consider restricting the use of vulnerable versions of Firefox and Thunderbird until patches are applied. Finally, maintain regular vulnerability scanning and asset inventory to ensure all instances of these applications are identified and updated promptly.
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Technical Details
- Data Version
- 5.1
- Assigner Short Name
- mozilla
- Date Reserved
- 2023-05-04T00:00:00
- Cvss Version
- null
- State
- PUBLISHED
Threat ID: 6835ef3f182aa0cae21b2734
Added to database: 5/27/2025, 4:58:39 PM
Last enriched: 7/6/2025, 2:57:26 AM
Last updated: 8/15/2025, 5:58:17 AM
Views: 15
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