# CVE-2026-41257: jqlang jq integer overflow in bytecode VM stack reallocation

Source: https://junglewise.ai/threats/cve-2026-41257-jqlang-jq-integer-overflow-in-bytecode-vm-stack-reallocation  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-11. Updated: 2026-05-14  
License: CC BY 4.0 with a link back

CVE-2026-41257 · Severity: medium · CVSS 5.5 · Published 2026-05-11

jq is a widely used command-line tool for processing and transforming JSON data. A vulnerability in its internal memory management allows a specially crafted JSON query to cause the program to crash or potentially corrupt system memory. This could lead to a denial-of-service or, in more complex scenarios, allow an attacker to execute unauthorized code if they can convince a user to run a malicious script.

Technologies: [Jqlang Jq](https://junglewise.ai/threats/technologies/jq). Vendors: [Jqlang](https://junglewise.ai/threats/vendors/jqlang).

## Quick answers

**Is CVE-2026-41257 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-41257 being exploited in the wild.

**How severe is CVE-2026-41257?** Medium severity, with a CVSS score of 5.5, published 11 May 2026.

**Which products and versions are affected?** Jqlang Jq <= 1.8.1.

**Is there a fix for CVE-2026-41257?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-41257 attacked?** It is attacked with local access, in a software library.

**Am I affected by CVE-2026-41257?** Check whether you run Jqlang Jq at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

An integer overflow vulnerability exists in the jq bytecode VM's data stack management within `src/exec_stack.h`. The stack uses a signed integer (`stack_ptr`) to track allocation sizes. When the stack grows beyond approximately 1 GiB via deeply nested generator forks, the doubling arithmetic in `stack_reallocate` overflows. This results in a truncated or wrapped value being passed to `realloc` and subsequently used in a `memmove` operation with attacker-influenced offsets. While often resulting in a Denial of Service (abort due to failed allocation), specific recursion depths could lead to an out-of-bounds heap write. No patch was available at the time of the advisory.

## Affected products

- jqlang jq <= 1.8.1

## Timeline

- 2026-04-24: advisory: GitHub Security Advisory published
- 2026-05-11: disclosed: CVE-2026-41257 published to NVD

## References

- [https://github.com/jqlang/jq/security/advisories/GHSA-4jm8-m363-4539](https://github.com/jqlang/jq/security/advisories/GHSA-4jm8-m363-4539)

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