CVE-2026-74988 in Firefox
Summary
by MITRE • 08/18/2026
Internally found bugs present in Firefox ESR 153.0 and Firefox 153. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited. This vulnerability was fixed in Firefox 154 and Firefox ESR 153.1.
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Analysis
by VulDB Data Team • 08/18/2026
The discovery of internal vulnerabilities within Mozilla Firefox versions 153.0 and the corresponding Extended Support Release (ESR) version 153 highlights critical risks associated with memory management and security-relevant defects in complex web browser architectures. These issues, identified during internal development cycles before public release or shortly thereafter, exhibited characteristics consistent with memory corruption errors such as buffer overflows, use-after-free conditions, or integer overflow vulnerabilities. Such flaws are particularly dangerous because they can allow an attacker to execute arbitrary code within the context of the victim process, potentially leading to full system compromise if sandboxing mechanisms fail to contain the breach. The presumption that these defects could be exploited with sufficient effort underscores their severity, as memory corruption bugs often serve as reliable primitives for achieving remote code execution in modern browsers where traditional stack-based exploits are mitigated by advanced security features like ASLR and DEP.
The operational impact of these vulnerabilities is significant given Firefox's widespread adoption across enterprise environments relying on the ESR branch for stability and long-term support. Users running version 153 were exposed to potential attacks via maliciously crafted web pages, specially constructed PDF files, or other content types processed by the browser engine. An attacker could leverage these flaws to bypass security boundaries, access sensitive user data such as cookies, session tokens, or saved passwords, and establish persistence on affected systems. The presence of memory corruption defects indicates a failure in boundary checks or lifecycle management within specific components like GeckoView or SpiderMonkey, which are core parts of the Firefox rendering engine and JavaScript interpreter respectively. These components handle untrusted input from web content, making them prime targets for exploitation attempts aimed at escaping the browser sandbox.
Mozilla addressed these issues by releasing patched versions in Firefox 154 and Firefox ESR 153.1, demonstrating a proactive approach to vulnerability management even when bugs are caught internally prior to widespread deployment or shortly after initial release. The fix likely involved rigorous code review, static analysis enhancements, and dynamic testing using fuzzing tools designed to detect memory safety violations. This rapid response cycle is crucial for maintaining the integrity of the browser ecosystem and preventing potential mass exploitation campaigns that often target newly discovered zero-day vulnerabilities in popular software. Organizations utilizing Firefox ESR must ensure their update policies are configured to automatically deploy these patches to minimize the window of exposure, as delayed updates leave critical infrastructure vulnerable to advanced persistent threats seeking to exploit known but unpatched flaws.
From a classification perspective, these memory corruption defects align with Common Weakness Enumeration categories such as CWE-120 Buffer Copy without Checking Size of Input and CWE-416 Use After Free, which are prevalent in C++ based applications like Firefox. In terms of the MITRE ATT&CK framework, successful exploitation would likely map to techniques under Initial Access via Spearphishing Attachment or Drive-by Compromise, followed by Execution through Command and Scripting Interpreter if arbitrary code execution is achieved. The mitigation strategy extends beyond simply applying patches; it includes enforcing strict content security policies, disabling unnecessary plugins or features that increase the attack surface, and ensuring that browser sandboxing configurations are optimized to limit the impact of any potential breach. Continuous monitoring for anomalous behavior in endpoint detection systems can also help identify attempts to exploit these specific memory corruption patterns before they result in full compromise.