CVE-2026-110816 ljharb CVE debrief

Who should care

Defenders handling untrusted input, especially in applications using the qs library, should assess exposure and prioritize verification and updates. They should review compensating controls for exposed systems while remediation is scheduled and verified. Defenders should also monitor applications for potential errors related to qs library and track exceptions, retest remediated assets, and close the item only after evidence is documented.

Why it matters

Defenders should care about this vulnerability as it can cause errors in applications handling untrusted input, and requires verification and updates of qs library versions.

• Potential errors in applications handling untrusted input
• Need for verification and updates of qs library versions
• Importance of validating input data

Technical summary

The qs library's `qs.stringify` function with `arrayFormat: 'comma'` throws a TypeError when an array element cannot be coerced to a string, such as an object with a non-callable `toString` property or a null-prototype object. This occurs because the comma format joins array elements with `Array.prototype.join` and, under `encodeValuesOnly`, first passes each element through `String()` in `utils.encode`. The vulnerability can cause errors in applications handling untrusted input and requires verification and updates of qs library versions.

Defensive priority

Defenders should prioritize verifying and updating qs library versions, especially in applications handling untrusted input, to prevent potential errors.

Recommended defensive actions

• Verify and update qs library versions to 6.16.1 or later
• Review and validate input data to prevent untrusted input
• Monitor applications for potential errors related to qs library
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up
• Review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance

Evidence notes

The CVE record and source item provide details on the vulnerability, including its description, affected versions, and references to vendor advisories and patches. The qs library's `qs.stringify` function with `arrayFormat: 'comma'` throws a TypeError when an array element cannot be coerced to a string. Defenders should verify and update qs library versions, especially in applications handling untrusted input, to prevent potential errors. The CVE record was published on 2026-10-14T22:05:24.015Z and has not been modified since then.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.