CVE-2026-47770 in jqlang
Summary
by MITRE • 06/25/2026
jq is a command-line JSON processor. Prior to 1.8.2, comparing two sufficiently deeply nested arrays with the == operator exhausts the C stack on jq's ordinary command-line surface, resulting in denial of service via stack exhaustion (uncontrolled recursion). The crash occurs in jq's recursive structural comparison code, with the recursion repeating through jvp_array_equal() and jv_equal() in src/jv.c when comparing deeply nested arrays; a nearby sort comparator path through jv_cmp() in src/jv_aux.c overflows the stack at a larger nesting depth from the same missing recursion guard. Anyone running jq comparisons on attacker-controlled deeply nested JSON values, or embedding jq in a context where untrusted data can reach the == comparison path, is affected. This vulnerability is fixed in 1.8.2.
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Analysis
by VulDB Data Team • 06/25/2026
The jq command-line JSON processor contains a critical stack exhaustion vulnerability affecting versions prior to 1.8.2. This vulnerability stems from uncontrolled recursion in the comparison logic when processing deeply nested arrays. The flaw manifests specifically during equality operations using the == operator, where the recursive structural comparison code fails to implement proper depth limits or recursion guards. The issue occurs in the core comparison functions jvp_array_equal() and jv_equal() located in src/jv.c, which repeatedly call themselves without adequate stack depth monitoring.
The vulnerability operates through a recursive descent pattern that consumes system stack resources rapidly when processing deeply nested JSON arrays. When jq encounters two arrays with excessive nesting levels, the comparison logic enters an infinite recursion loop that exhausts the C stack space allocated to the process. This recursive behavior is particularly dangerous because it can be triggered by attacker-controlled input, making it a significant denial of service vector. The same underlying issue affects the sorting comparator path through jv_cmp() in src/jv_aux.c, though this path requires even deeper nesting to trigger the stack overflow.
The operational impact of this vulnerability extends beyond simple denial of service, as it can be exploited in contexts where jq processes untrusted JSON data from external sources. Systems that embed jq within applications or services where user input directly reaches comparison operations are particularly vulnerable. The vulnerability maps to CWE-674, which specifically addresses "Uncontrolled Recursion" and falls under the broader category of stack-based buffer overflow conditions. From an attack perspective, this represents a straightforward denial of service exploit requiring minimal resources to execute successfully.
Mitigation strategies include upgrading to jq version 1.8.2 or later, where proper recursion guards have been implemented to prevent uncontrolled stack consumption. Organizations should also implement input validation and sanitization measures to limit the depth of JSON structures processed by jq when handling untrusted data. Additionally, deployment environments should consider implementing resource limits and process monitoring to detect and prevent stack exhaustion attacks. The fix addresses both code paths mentioned in the vulnerability description, ensuring that recursive comparison operations maintain proper stack depth checks and prevent infinite recursion scenarios that could lead to system instability or complete service disruption.