CVE-2025-10533 is an integer overflow vulnerability identified in the SVG (Scalable Vector Graphics) component of Mozilla Firefox browsers prior to version 143, including Firefox ESR versions below 115.28 and 140.3. An integer overflow occurs when an arithmetic operation attempts to create a numeric value that is outside the range that can be represented with a given number of bits, causing the value to wrap around unexpectedly. In the context of the SVG component, this can lead to memory corruption, potentially allowing an attacker to execute arbitrary code, cause a denial of service (crash), or bypass security controls. SVG is widely used for rendering vector graphics in web pages, and a vulnerability in this component can be triggered by maliciously crafted SVG content embedded in web pages or delivered through other vectors such as email or documents that render SVG. The lack of a CVSS score and absence of known exploits in the wild suggest this vulnerability is newly disclosed and not yet actively exploited. However, the nature of integer overflows in complex rendering engines like Firefox’s SVG parser typically represents a significant security risk, especially given Firefox’s widespread use. The vulnerability affects multiple Firefox versions, including ESR (Extended Support Release) versions commonly used in enterprise environments, indicating a broad impact surface. No patch links are provided, implying that fixes may still be pending or recently released without public documentation. Given the critical role of browsers as a primary attack vector, exploitation could allow remote attackers to compromise user systems without authentication or user interaction beyond visiting a malicious or compromised website.

For European organizations, this vulnerability poses a substantial risk due to the widespread use of Firefox, including in government, education, and private sectors. Exploitation could lead to unauthorized access to sensitive data, disruption of services through browser crashes, or full system compromise if the attacker achieves code execution. This is particularly concerning for organizations handling sensitive personal data under GDPR, where breaches can result in significant regulatory penalties. The vulnerability could also be leveraged in targeted attacks against high-value entities such as financial institutions, critical infrastructure operators, and governmental bodies. Since Firefox ESR versions are commonly deployed in enterprise environments for their stability and extended support, organizations using these versions are directly impacted. The lack of known exploits currently provides a window for proactive mitigation, but the potential for future exploitation remains high. Additionally, the vulnerability could be used as a foothold in multi-stage attacks, enabling lateral movement within networks or data exfiltration.

European organizations should prioritize updating Firefox browsers to versions 143 or later, and Firefox ESR to versions 115.28 or 140.3 and above as soon as patches become available. Until patches are applied, organizations should consider implementing network-level protections such as web filtering to block access to untrusted or suspicious websites that may host malicious SVG content. Employing endpoint protection solutions capable of detecting anomalous browser behavior or memory corruption attempts can provide additional defense layers. Security teams should monitor Mozilla’s official channels for patch releases and advisories related to this vulnerability. User awareness training should emphasize caution when interacting with unfamiliar web content. In environments where immediate patching is not feasible, disabling SVG rendering or restricting browser capabilities through group policies or browser configuration management could mitigate risk, though this may impact user experience. Finally, organizations should review their incident detection capabilities to identify potential exploitation attempts, including monitoring for unusual browser crashes or network traffic indicative of exploitation attempts.