CVE-2025-15284VulnerabilityPublished 29 Dec 2025Updated 10 Feb 2026

CVE-2025-15284: qs · Improper Input Validation

Affects qsSource CVE Database V5

Not known to be exploited · CVSS 6.3 Medium : upgrade to 6.14.1 when convenient.

Data as of 26 Oct 2026, 06:26 UTC

CVSS 4.0 base score

6.3Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.4% chance of exploitation in 30 days – higher than 38% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 6.14.1

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:L

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: Present
Privileges Required: None
User Interaction: None
Vulnerable system confidentiality: None
Vulnerable system integrity: None
Vulnerable system availability: Low
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: Low

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: Present: The successful attack depends on the presence of specific deployment and execution conditions of the vulnerable system that enable the attack. These include: a race condition must be won to successfully exploit the vulnerability (the successfulness of the attack is conditioned on execution conditions that are not under full control of the attacker, or the attack may need to be launched multiple times against a single target before being successful); the attacker must inject themselves into the logical network path between the target and the resource requested by the victim (e.g. vulnerabilities requiring an on-path attacker).
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: None: There is no loss of confidentiality within the Vulnerable System.
Vulnerable system integrity: None: There is no loss of integrity within the Vulnerable System.
Vulnerable system availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the Vulnerable System are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the Subsequent System are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the Subsequent System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 29 Dec 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-26.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade qs to 6.14.1.

Affected software

Product	Affected	Fixed in
npmqs`pkg:npm/qs`Other threats	Affected <6.14.1	Fixed in 6.14.1

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

1. Upgrade the qs library to version 6.14.1 or later, where the arrayLimit enforcement bug is fixed. 2. Review and enforce strict parameterLimit settings, ideally retaining the default value of 1000 or lower, to cap the total number of parameters parsed and limit resource consumption. 3. Implement input validation and rate limiting at the web application firewall (WAF) or API gateway level to detect and block unusually large or malformed query strings with excessive array elements. 4. Monitor application logs for abnormal spikes in query string parameter counts or parsing errors indicative of attempted exploitation. 5. Conduct security testing and code audits to identify other potential input validation weaknesses in query string parsing or related components. 6. Educate development teams on secure configuration of third-party libraries and the risks of overriding default limits without proper safeguards. 7. Deploy resource usage monitoring and automated alerting to detect early signs of denial of service conditions. 8. Consider isolating critical services behind reverse proxies or load balancers that can enforce stricter request size limits and filtering.

Description

Improper Input Validation vulnerability in qs (parse modules) allows HTTP DoS.This issue affects qs: < 6.14.1. Summary The arrayLimit option in qs did not enforce limits for bracket notation (a[]=1&a[]=2), only for indexed notation (a[0]=1). This is a consistency bug; arrayLimit should apply uniformly across all array notations. Note: The default parameterLimit of 1000 effectively mitigates the DoS scenario originally described. With default options, bracket notation cannot produce arrays larger than parameterLimit regardless of arrayLimit, because each a[]=valueconsumes one parameter slot. The severity has been reduced accordingly. Details The arrayLimit option only checked limits for indexed notation (a[0]=1&a[1]=2) but did not enforce it for bracket notation (a[]=1&a[]=2). Vulnerable code (lib/parse.js:159-162): if (root === '[]' && options.parseArrays) { obj = utils.combine([], leaf); // No arrayLimit check } Working code (lib/parse.js:175): else if (index <= options.arrayLimit) { // Limit checked here obj = []; obj[index] = leaf; } The bracket notation handler at line 159 uses utils.combine([], leaf) without validating against options.arrayLimit, while indexed notation at line 175 checks index <= options.arrayLimit before creating arrays. PoC const qs = require('qs'); const result = qs.parse('a[]=1&a[]=2&a[]=3&a[]=4&a[]=5&a[]=6', { arrayLimit: 5 }); console.log(result.a.length); // Output: 6 (should be max 5) Note on parameterLimit interaction: The original advisory's "DoS demonstration" claimed a length of 10,000, but parameterLimit (default: 1000) caps parsing to 1,000 parameters. With default options, the actual output is 1,000, not 10,000. Impact Consistency bug in arrayLimit enforcement. With default parameterLimit, the practical DoS risk is negligible since parameterLimit already caps the total number of parsed parameters (and thus array elements from bracket notation). The risk increases only when parameterLimit is explicitly set to a very high value.

Impact

For European organizations, the primary impact of this vulnerability is the potential for denial of service attacks against web applications or APIs that utilize vulnerable versions of the qs library for query string parsing. If parameterLimit is configured higher than the default or disabled, attackers can send crafted HTTP requests with large bracket notation arrays to exhaust server memory and CPU resources, leading to degraded performance or service outages. This can disrupt business operations, cause downtime, and potentially impact customer trust and regulatory compliance, especially under GDPR requirements for service availability. The vulnerability does not directly expose sensitive data or allow code execution, limiting confidentiality and integrity impacts. However, availability degradation can affect critical services, particularly for sectors relying heavily on web-based interfaces such as finance, healthcare, and government services. Organizations using custom configurations with high parameterLimit values or those unaware of the vulnerability risk increased exposure. The lack of authentication or user interaction requirements makes exploitation feasible by remote attackers scanning for vulnerable endpoints.

Summary

CVE-2025-15284 is a vulnerability in the qs Node.js library, which is widely used for parsing URL query strings. The issue arises from inconsistent enforcement of the arrayLimit option, which is intended to restrict the maximum number of elements in parsed arrays. While the arrayLimit correctly limits arrays using indexed notation (e.g., a[0]=1&a[1]=2), it fails to enforce this limit for bracket notation arrays (e.g., a[]=1&a[]=2). This inconsistency allows an attacker to craft HTTP query strings with bracket notation arrays exceeding the configured arrayLimit, potentially causing excessive memory allocation and CPU usage during parsing. The vulnerable code path combines array elements without checking the arrayLimit, whereas the indexed notation path enforces the limit properly. Although the original advisory demonstrated a denial of service scenario with 10,000 elements, the default parameterLimit of 1000 parameters caps the total number of parsed parameters, effectively mitigating large-scale exploitation under default settings. The vulnerability affects qs versions prior to 6.14.1, which fixed the issue by applying arrayLimit checks uniformly. Exploitation requires no authentication or user interaction and can be triggered remotely by sending specially crafted HTTP requests with large bracket notation arrays. The CVSS 4.0 vector (AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:L) indicates network attack vector, low complexity, partial attack type requiring no privileges or user interaction, with low impact on availability. No known exploits are currently in the wild.

CWE-20Improper Input Validation (opens in a new tab)
Class weaknessLikelihood of exploit: HighCWE Top 25 (2025): #18OWASP Top 10 A05:2025: Injection (opens in a new tab)
The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.
MITRE discourages mapping vulnerabilities to this broad entry; the root cause is usually a more specific weakness.
Architecture and Design · Attack Surface Reduction
Consider using language-theoretic security (LangSec) techniques that characterize inputs using a formal language and build "recognizers" for that language. This effectively requires parsing to be a distinct layer that effectively enforces a boundary between raw input and internal data representations, instead of…
Architecture and Design · Libraries or Frameworks
Use an input validation framework such as Struts or the OWASP ESAPI Validation API. Note that using a framework does not automatically address all input validation problems; be mindful of weaknesses that could arise from misusing the framework itself (CWE-1173).
Architecture and Design · Implementation · Attack Surface Reduction
Understand all the potential areas where untrusted inputs can enter the product, including but not limited to: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any…
OWASP Cheat Sheets
XML Security (opens in a new tab)
Mass Assignment (opens in a new tab)
Injection Prevention (opens in a new tab)
SQL Injection Prevention (opens in a new tab)
Injection Prevention in Java (opens in a new tab)
OWASP ASVS 4.0.3
V13.3.1 (opens in a new tab)
V5.1.4 (opens in a new tab)
V5.1.3 (opens in a new tab)
Attack patterns
Buffer Overflow via Environment Variables (opens in a new tab)
Server Side Include (SSI) Injection (opens in a new tab)
Cross Zone Scripting (opens in a new tab)
Command Line Execution through SQL Injection (opens in a new tab)
Object Relational Mapping Injection (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 11 Feb 2026, 10:52 UTC

WeaknessesCWE-20

Technical details

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