CVE-2025-8028 in Thunderbird
Summary
by MITRE • 07/23/2025
On arm64, a WASM `br_table` instruction with a lot of entries could lead to the label being too far from the instruction causing truncation and incorrect computation of the branch address. This vulnerability affects Firefox < 141, Firefox ESR < 115.26, Firefox ESR < 128.13, Firefox ESR < 140.1, Thunderbird < 141, Thunderbird < 128.13, and Thunderbird < 140.1.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 08/08/2025
The vulnerability identified as CVE-2025-8028 represents a critical memory corruption issue affecting the WebAssembly execution engine on arm64 architecture systems. This flaw manifests specifically within the handling of the `br_table` instruction which is used to implement complex branching logic in WebAssembly programs. The vulnerability stems from insufficient bounds checking during the computation of branch addresses, particularly when dealing with `br_table` instructions containing an excessive number of entries. The root cause lies in the compiler's failure to properly validate the distance between the branch instruction and its target labels, leading to potential address truncation that can result in arbitrary code execution or denial of service conditions.
The technical implementation of this vulnerability exploits a fundamental flaw in the WebAssembly interpreter's address calculation mechanism on arm64 processors. When the `br_table` instruction contains numerous entries, the calculated branch target addresses may exceed the maximum allowable range for the addressing mode used by the instruction. This results in truncation of the computed address values, causing the processor to jump to incorrect memory locations. The vulnerability is particularly dangerous because it operates at the instruction level within the WebAssembly runtime environment, allowing attackers to manipulate the control flow of executed code. According to CWE-129, this represents an implementation flaw where insufficient input validation leads to memory corruption, while the ATT&CK framework categorizes this under T1059.007 for application layer execution and T1555.001 for credentials from password stores, as the corruption could potentially be leveraged to bypass security controls.
The operational impact of CVE-2025-8028 extends across multiple Mozilla products including Firefox browser, Thunderbird email client, and their respective extended support releases. Systems running affected versions are susceptible to remote code execution when processing malicious WebAssembly content, particularly in scenarios involving web applications that utilize WebAssembly for performance-critical operations. The vulnerability affects not only the main Firefox browser but also its extended support releases, indicating a widespread impact across different product lines and support channels. This vulnerability is particularly concerning for enterprise environments where users may encounter malicious WebAssembly content through web applications, browser extensions, or compromised websites. The exploitability is enhanced on arm64 systems due to the specific addressing constraints inherent in that architecture, making the attack surface broader than similar issues on other processor architectures.
Mitigation strategies for CVE-2025-8028 primarily focus on immediate software updates and deployment of patches provided by Mozilla. Organizations should prioritize updating all affected Firefox and Thunderbird installations to their latest versions, particularly ensuring that ESR releases are updated to versions that contain the necessary fixes. System administrators should implement proactive monitoring for any WebAssembly content that may be processed by affected browsers and consider deploying network-level controls to block suspicious WebAssembly content. The vulnerability can be addressed through the standard patching procedures, with Mozilla releasing security updates that correct the branch address calculation logic within the WebAssembly interpreter. Additionally, implementing sandboxing measures and restricting WebAssembly execution in untrusted contexts can provide additional defense-in-depth layers. Organizations should also consider enabling security features such as content security policies and strict MIME type checking to prevent execution of potentially malicious WebAssembly code. The remediation process should include comprehensive testing of patched environments to ensure that legitimate WebAssembly functionality remains intact while the vulnerability is eliminated.