CVE-2025-9182 in Thunderbird
Summary
by MITRE • 08/20/2025
Denial-of-service due to out-of-memory in the Graphics: WebRender component. This vulnerability affects Firefox < 142, Firefox ESR < 140.2, Thunderbird < 142, and Thunderbird < 140.2.
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Analysis
by VulDB Data Team • 10/31/2025
The vulnerability identified as CVE-2025-9182 represents a critical denial-of-service condition within the Graphics: WebRender component of Mozilla Firefox and Thunderbird applications. This issue stems from improper memory management during graphics rendering operations, specifically when processing malformed or malicious web content that triggers excessive memory allocation. The flaw manifests when the WebRender subsystem attempts to handle certain graphic elements or rendering commands that cause it to consume an unbounded amount of system memory, ultimately leading to application crashes or complete system resource exhaustion. This vulnerability impacts a wide range of affected versions including Firefox versions prior to 142 and Firefox ESR versions prior to 140.2, as well as Thunderbird versions prior to 142 and Thunderbird ESR versions prior to 140.2, making it a significant concern for organizations relying on these email and web browsers.
The technical root cause of this vulnerability lies in the memory allocation patterns within the WebRender graphics subsystem, which is designed to accelerate web content rendering through hardware acceleration and parallel processing. When encountering specific graphic rendering scenarios, particularly those involving complex CSS properties, WebGL operations, or malformed SVG elements, the WebRender component fails to implement proper bounds checking or memory limiting mechanisms. This allows an attacker to craft malicious web pages or email content that, when rendered, causes the graphics subsystem to continuously allocate memory without adequate cleanup or termination conditions. The flaw operates as a memory exhaustion attack where the application's memory usage grows uncontrollably until system resources are depleted, resulting in application crashes or system instability. According to CWE classification, this vulnerability aligns with CWE-400: Uncontrolled Resource Consumption, which encompasses issues where resource consumption is not properly bounded or controlled. The vulnerability also maps to ATT&CK technique T1499.004: Network Denial of Service, as it can be exploited to cause service disruption through resource exhaustion.
The operational impact of CVE-2025-9182 extends beyond simple application instability, potentially enabling more sophisticated attack vectors when combined with other vulnerabilities or when executed in targeted environments. An attacker could leverage this vulnerability to perform persistent denial-of-service attacks against users of affected browsers, making it particularly dangerous in enterprise environments where browser stability is critical for business operations. The vulnerability's exploitation requires minimal user interaction, typically only the viewing of a malicious webpage or opening of a specially crafted email message containing harmful graphics content. Organizations running affected versions of Firefox or Thunderbird face significant risk of service disruption, user productivity loss, and potential escalation to more severe security incidents if not properly mitigated. The vulnerability affects both desktop and mobile browser implementations, making it particularly concerning for organizations with diverse device ecosystems. The memory exhaustion nature of the flaw means that even a single malicious page could cause complete system instability, potentially affecting other running applications and system performance. Given the widespread use of Firefox and Thunderbird across both consumer and enterprise environments, this vulnerability represents a substantial risk to digital infrastructure security.
Mitigation strategies for CVE-2025-9182 should prioritize immediate patching of affected applications to the latest stable versions where the vulnerability has been resolved. Organizations should implement comprehensive patch management procedures to ensure all affected systems are updated promptly, as the vulnerability affects multiple product lines including both standard and extended support releases. Security teams should also consider implementing additional protective measures such as browser hardening configurations, content filtering solutions, and network-based restrictions on potentially malicious content. The WebRender component can be temporarily disabled through specific browser configuration settings, though this may impact performance and functionality of web applications. Network administrators should monitor for suspicious web traffic patterns that might indicate exploitation attempts, particularly focusing on content delivery from known malicious sources. Regular security assessments and vulnerability scanning should be conducted to identify any remaining instances of affected software within the organization's infrastructure. Organizations should also develop incident response procedures specifically addressing this vulnerability type, including user education on recognizing potentially malicious web content and establishing clear protocols for reporting suspected exploitation attempts. The mitigation approach should align with industry best practices for resource consumption control and memory management as outlined in various cybersecurity frameworks and standards including NIST SP 800-53 and ISO/IEC 27001.