Attack Chain

1. The attacker crafts a malicious JSON input specifically designed to trigger a signed-integer overflow in the decNumber D2U() macro within the jq application.
2. The attacker provides the malicious JSON input to the jq application as an argument or via standard input.
3. jq processes the JSON input, and the decNumber D2U() macro is invoked during the parsing or processing of the JSON data.
4. The signed-integer overflow occurs within the decNumber D2U() macro, leading to an incorrect calculation of memory allocation size.
5. The incorrect size leads to a write operation that goes beyond the intended boundaries of the stack buffer, causing a wild stack write.
6. The wild stack write overwrites sensitive data on the stack, such as return addresses or function pointers.
7. If the attacker has successfully overwritten a return address or function pointer, the execution flow can be redirected to an attacker-controlled address.
8. The attacker gains arbitrary code execution within the context of the jq application.

Impact

Successful exploitation of CVE-2026-43894 can lead to arbitrary code execution. The vulnerability impacts any system running a vulnerable version of jq. This can result in a complete compromise of the affected system, allowing attackers to steal sensitive information, install malware, or perform other malicious activities. The affected sectors would be those utilizing the jq utility for JSON processing. The number of potential victims depends on the prevalence of the vulnerable jq version.

Recommendation

• Upgrade jq to the latest patched version that addresses CVE-2026-43894 to remediate the vulnerability.
• Deploy the Sigma rules provided below to your SIEM to detect potential exploitation attempts of CVE-2026-43894.
• Monitor systems utilizing jq for unusual behavior, such as unexpected crashes or unauthorized access attempts, using process_creation and file_event logs.