CVE-2026-82562

Summary

When qs.parse is called with comma: true and throwOnLimitExceeded: true, a comma-separated value under a bracket-push key (a[]=1,2,3,4) is split into an array without being compared against arrayLimit, while the same value under a flat key (a=1,2,3,4), an indexed key (a[0]=), a nested key (a[b]=), or a dotted key (a.b= with allowDots) throws the documented RangeError. A single parameter such as a[]=1,2,2,... therefore produces an inner array of arbitrary length even though the caller opted into the hard limit. This is the []= key form that the fix for CVE-2026-2391 (qs 6.14.2) did not cover.

Details

In lib/parse.js, a comma-separated value under a []= key is split and then wrapped as a single nested element (val = [val], so that each a[]=x,y group counts as one element of the outer array). The arrayLimit check that 6.14.2 added for comma values runs after that wrap, so for []= parts it only ever saw the wrapper of length 1. 6.15.3 added a pre-split comma count so that an oversized value throws before it is allocated, but gated it on an isFlatArrayValue flag that parseValues set to false for any part containing []=, and did not pass it for object-valued input, so the gap remained.

PoC

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var qs = require(qs);



var options = { comma: true, arrayLimit: 3, throwOnLimitExceeded: true };



qs.parse(a=1,2,3,4, options);   // RangeError: Array limit exceeded. Only 3 elements allowed in an array.



qs.parse(a[]=1,2,3,4, options); // { a: [ [ 1, 2, 3, 4 ] ] }  (no throw)



qs.parse(a[]= + 1,.repeat(1000000) + 1, { comma: true, arrayLimit: 20, throwOnLimitExceeded: true });



// no throw; a 1,000,001-element inner array is allocated

Fix

lib/parse.js, applied in 8859c37 on main and released as v6.16.0: the isFlatArrayValue gate is removed, so every comma-split value is counted against arrayLimit before splitting regardless of key form. An in-limit group under a[]= still counts as one element of the outer array, and the default (throwOnLimitExceeded: false) path is unchanged.

Affected versions

>=6.14.2 <6.16.0, fixed in v6.16.0.

v6.14.2 introduced arrayLimit enforcement for comma values (the fix for CVE-2026-2391) but only for values not under a []= key, and every release from v6.14.2 through v6.15.3 has the same gap. v6.14.0 and v6.14.1, where throwOnLimitExceeded exists but does not apply to any comma form, are covered by CVE-2026-2391 rather than this record. Earlier lines (6.7.x through 6.13.x) have comma but no throwOnLimitExceeded, so there is no hard cap on any comma path to bypass; releases before 6.7.0 have no comma option.

Impact

An unauthenticated attacker who can reach an application that parses untrusted query strings or urlencoded bodies with both comma: true and throwOnLimitExceeded: true (both non-default) can bypass the configured limit with a single a[]= parameter and force the parser to allocate an array proportional to the request size. The cost is strictly linear in the attacker-supplied bytes (about 0.1 microseconds and 6 to 7 retained bytes per input byte; the same out-of-memory threshold as the documented default throwOnLimitExceeded: false path), so a transport-layer request or body size limit bounds it completely (and nodes default maximum HTTP header size of 16 KB already bounds the request line, so multi-megabyte payloads need a body parser). The impact is that an opt-in hard limit fails open on one key spelling, not unbounded allocation from a small input.

Weakness

The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.

Affected Software

Name	Vendor	Start Version	End Version
Red Hat Hardened Images	RedHat	grafana12-4-main-12.4.9-0.4.hum1	*
Red Hat Hardened Images	RedHat	grafana13-1-main-13.1.3-0.4.hum1	*
Red Hat Hardened Images	RedHat	grafana13-2-main-13.2.1-0.1.hum1	*
Red Hat OpenShift Dev Spaces 3.30	RedHat	devspaces/dashboard-rhel9:1789162884	*
Node-qs	Ubuntu	upstream	*

Potential Mitigations

Assume all input is malicious. Use an “accept known good” input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, “boat” may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as “red” or “blue.”
Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code’s environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
Mitigation of resource exhaustion attacks requires that the target system either:
The first of these solutions is an issue in itself though, since it may allow attackers to prevent the use of the system by a particular valid user. If the attacker impersonates the valid user, they may be able to prevent the user from accessing the server in question.
The second solution can be difficult to effectively institute – and even when properly done, it does not provide a full solution. It simply requires more resources on the part of the attacker.
If the program must fail, ensure that it fails gracefully (fails closed). There may be a temptation to simply let the program fail poorly in cases such as low memory conditions, but an attacker may be able to assert control before the software has fully exited. Alternately, an uncontrolled failure could cause cascading problems with other downstream components; for example, the program could send a signal to a downstream process so the process immediately knows that a problem has occurred and has a better chance of recovery.
Ensure that all failures in resource allocation place the system into a safe posture.
Use quotas or other resource-limiting settings provided by the operating system or environment. For example, when managing system resources in POSIX, setrlimit() can be used to set limits for certain types of resources, and getrlimit() can determine how many resources are available. However, these functions are not available on all operating systems.
When the current levels get close to the maximum that is defined for the application (see CWE-770), then limit the allocation of further resources to privileged users; alternately, begin releasing resources for less-privileged users. While this mitigation may protect the system from attack, it will not necessarily stop attackers from adversely impacting other users.
Ensure that the application performs the appropriate error checks and error handling in case resources become unavailable (CWE-703).

NVD	https://nvd.nist.gov/vuln/detail/CVE-2026-82562
CWE	https://cwe.mitre.org/data/definitions/770.html

Allocation of Resources Without Limits or Throttling

Summary

Details

PoC

Fix

Affected versions

Impact

Weakness

Affected Software

Potential Mitigations

References

CVE-2026-82562

Allocation of Resources Without Limits or Throttling

Summary

Details

PoC

Fix

Affected versions

Impact

Weakness

Affected Software

Potential Mitigations

Related Attack Patterns

References