express-5.2.1.tgz: 7 vulnerabilities (highest severity is: 9.1)

[mend-for-github-com]

Vulnerable Library - express-5.2.1.tgz

Sample Path to Dependency File: /package.json

Path to vulnerable library: /package.json

Vulnerabilities

Vulnerability	Severity	CVSS	Dependency	Type	Fixed in (express version)	Remediation Possible**
CVE-2026-90711	Critical	9.1	proxy-addr-2.0.7.tgz	Transitive	N/A*	❌
CVE-2026-4926	High	7.5	path-to-regexp-8.3.0.tgz	Transitive	N/A*	❌
CVE-2026-4923	Medium	5.9	path-to-regexp-8.3.0.tgz	Transitive	N/A*	❌
CVE-2026-8723	Medium	5.3	qs-6.14.1.tgz	Transitive	N/A*	❌
CVE-2026-82417	Medium	5.3	qs-6.14.1.tgz	Transitive	N/A*	❌
CVE-2026-2391	Low	3.7	qs-6.14.1.tgz	Transitive	N/A*	❌
CVE-2026-12590	Low	3.7	body-parser-2.2.2.tgz	Transitive	N/A*	❌

*For some transitive vulnerabilities, there is no version of direct dependency with a fix. Check the "Details" section below to see if there is a version of transitive dependency where vulnerability is fixed.

**In some cases, Remediation PR cannot be created automatically for a vulnerability despite the availability of remediation

Details

CVE-2026-90711

Vulnerable Library - proxy-addr-2.0.7.tgz

Determine address of proxied request

Library home page: https://registry.npmjs.org/proxy-addr/-/proxy-addr-2.0.7.tgz

Sample Path to Dependency File: /package.json

Path to vulnerable library: /package.json

Dependency Hierarchy:

• express-5.2.1.tgz (Root Library)
  • ❌ proxy-addr-2.0.7.tgz (Vulnerable Library)

Found in base branch: main

Vulnerability Details

proxy-addr is a Node.js module that determines a request's client address behind trusted reverse proxies, and it backs Express req.ip and req.ips. In versions 1.1.0 through 2.0.7, a trust subnet written in IPv4-mapped IPv6 notation with an IPv4-sized prefix, such as ::ffff:10.0.0.0/8 instead of the correct ::ffff:10.0.0.0/104, is accepted without error but trusts every IPv4 address on the internet rather than the block it names. Because the socket peer then becomes trusted at hop 0, any unauthenticated client can supply an arbitrary X-Forwarded-For header and control the address the application reads, which defeats IP-based access control, rate limiting, geolocation, and audit logging. This is a fail-open regression introduced in version 1.1.0. The issue is fixed in proxy-addr 2.0.8, and users should upgrade to 2.0.8 or later. As a workaround, ensure any IPv4-mapped IPv6 trust subnet uses a prefix length of at least 97, or express the range in plain IPv4 notation.

Publish Date: 2026-09-15

URL: CVE-2026-90711

CVSS 3 Score Details (9.1)

Base Score Metrics:

• Exploitability Metrics:
  • Attack Vector: Network
  • Attack Complexity: Low
  • Privileges Required: None
  • User Interaction: None
  • Scope: Unchanged
• Impact Metrics:
  • Confidentiality Impact: High
  • Integrity Impact: High
  • Availability Impact: None

For more information on CVSS3 Scores, click here.

Suggested Fix

Type: Upgrade version

Release Date: 2026-09-15

Fix Resolution: proxy-addr - 2.0.8,https://github.com/jshttp/proxy-addr.git - v2.0.8

CVE-2026-4926

Vulnerable Library - path-to-regexp-8.3.0.tgz

Express style path to RegExp utility

Library home page: https://registry.npmjs.org/path-to-regexp/-/path-to-regexp-8.3.0.tgz

Sample Path to Dependency File: /package.json

Path to vulnerable library: /package.json

Dependency Hierarchy:

• express-5.2.1.tgz (Root Library)
  • router-2.2.0.tgz
    • ❌ path-to-regexp-8.3.0.tgz (Vulnerable Library)

Found in base branch: main

Vulnerability Details

Impact:A bad regular expression is generated any time you have multiple sequential optional groups (curly brace syntax), such as "{a}{b}{c}:z". The generated regex grows exponentially with the number of groups, causing denial of service.Patches:Fixed in version 8.4.0.Workarounds:Limit the number of sequential optional groups in route patterns. Avoid passing user-controlled input as route patterns.

Publish Date: 2026-03-26

URL: CVE-2026-4926

CVSS 3 Score Details (7.5)

Base Score Metrics:

• Exploitability Metrics:
  • Attack Vector: Network
  • Attack Complexity: Low
  • Privileges Required: None
  • User Interaction: None
  • Scope: Unchanged
• Impact Metrics:
  • Confidentiality Impact: None
  • Integrity Impact: None
  • Availability Impact: High

For more information on CVSS3 Scores, click here.

Suggested Fix

Type: Upgrade version

Origin: GHSA-j3q9-mxjg-w52f

Release Date: 2026-03-26

Fix Resolution: path-to-regexp - 8.4.0

CVE-2026-4923

Vulnerable Library - path-to-regexp-8.3.0.tgz

Express style path to RegExp utility

Library home page: https://registry.npmjs.org/path-to-regexp/-/path-to-regexp-8.3.0.tgz

Sample Path to Dependency File: /package.json

Path to vulnerable library: /package.json

Dependency Hierarchy:

• express-5.2.1.tgz (Root Library)
  • router-2.2.0.tgz
    • ❌ path-to-regexp-8.3.0.tgz (Vulnerable Library)

Found in base branch: main

Vulnerability Details

Impact:
When using multiple wildcards, combined with at least one parameter, a regular expression can be generated that is vulnerable to ReDoS. This backtracking vulnerability requires the second wildcard to be somewhere other than the end of the path.
Unsafe examples:
/*foo-*bar-:baz
/*a-:b-*c-:d
/x/*a-:b/*c/y
Safe examples:
/*foo-:bar
/*foo-:bar-*baz
Patches:
Upgrade to version 8.4.0.
Workarounds:
If you are using multiple wildcard parameters, you can check the regex output with a tool such as https://makenowjust-labs.github.io/recheck/playground/ to confirm whether a path is vulnerable.

Publish Date: 2026-03-26

URL: CVE-2026-4923

CVSS 3 Score Details (5.9)

Base Score Metrics:

• Exploitability Metrics:
  • Attack Vector: Network
  • Attack Complexity: High
  • Privileges Required: None
  • User Interaction: None
  • Scope: Unchanged
• Impact Metrics:
  • Confidentiality Impact: None
  • Integrity Impact: None
  • Availability Impact: High

For more information on CVSS3 Scores, click here.

Suggested Fix

Type: Upgrade version

Origin: GHSA-27v5-c462-wpq7

Release Date: 2026-03-26

Fix Resolution: path-to-regexp - 8.4.0

CVE-2026-8723

Vulnerable Library - qs-6.14.1.tgz

A querystring parser that supports nesting and arrays, with a depth limit

Library home page: https://registry.npmjs.org/qs/-/qs-6.14.1.tgz

Sample Path to Dependency File: /package.json

Path to vulnerable library: /package.json

Dependency Hierarchy:

• express-5.2.1.tgz (Root Library)
  • ❌ qs-6.14.1.tgz (Vulnerable Library)

Found in base branch: main

Vulnerability Details

Summary
"qs.stringify" throws "TypeError" when called with "arrayFormat: 'comma'" and "encodeValuesOnly: true" on an array containing "null" or "undefined". The throw is synchronous and not handled by any of qs's null-related options ("skipNulls", "strictNullHandling").
Details
In the comma + "encodeValuesOnly" branch, "lib/stringify.js:145" mapped the array through the raw encoder before joining:
"utils.encode" ("lib/utils.js:195") reads "str.length" with no null guard, so a "null" or "undefined" element throws "TypeError". "skipNulls" and "strictNullHandling" are both checked in the per-element loop below this line and never get a chance to run.
Same class of bug as the filter-array path fixed in 0c180a4. The vulnerable shape of the comma + "encodeValuesOnly" branch was introduced in 4c4b23d ("encode comma values more consistently", PR #⁠463, 2023-01-19), first released in v6.11.1.
PoC
Fix
"lib/stringify.js:145", applied in 21f80b3 on "main" and released as v6.15.2:
"null" and "undefined" now pass through "maybeMap" unchanged and reach the "join(',')" step as-is. For "{ a: [null, 'b'] }" this produces "a=,b", matching the non-"encodeValuesOnly" comma path (which already joins before encoding and produces "a=%2Cb" for the same input). Single-element "[null]" arrays still collapse via the existing "obj.join(',') || null" and remain subject to "skipNulls" / "strictNullHandling" in the main loop.
Affected versions
">=6.11.1 <6.15.2" — fixed in v6.15.2.
The vulnerable code shape was introduced in 4c4b23d and first shipped in v6.11.1. Earlier versions — including all of 6.7.x, 6.8.x, 6.9.x, 6.10.x, and 6.11.0 — implemented the comma + "encodeValuesOnly" path differently (joining before encoding) and are not affected. Empirically verified across released versions.
Impact
Application code that calls "qs.stringify" with both "arrayFormat: 'comma'" and "encodeValuesOnly: true" (both non-default) on input that may contain a "null" or "undefined" array element will throw synchronously instead of producing a query string. In a typical Node.js HTTP framework (Express, Fastify, Koa, hapi) the sync throw is caught by the framework's error boundary and the affected request returns a 500; the worker process does not exit and subsequent requests are unaffected. The "kills the worker process" framing applies only to call sites outside a request-handler error boundary (background jobs, startup paths, stream pipelines) or to deployments with framework error handling explicitly disabled.
The vulnerable input is a "null" or "undefined" entry inside an array; this is reachable from JSON request bodies or from application code constructing arrays from user input, but not from standard HTML form submissions (which produce strings or omitted fields, not literal "null").
Mend Note: The description of this vulnerability differs from MITRE.

Publish Date: 2026-05-16

URL: CVE-2026-8723

CVSS 3 Score Details (5.3)

Base Score Metrics:

• Exploitability Metrics:
  • Attack Vector: Network
  • Attack Complexity: Low
  • Privileges Required: None
  • User Interaction: None
  • Scope: Unchanged
• Impact Metrics:
  • Confidentiality Impact: None
  • Integrity Impact: None
  • Availability Impact: Low

For more information on CVSS3 Scores, click here.

Suggested Fix

Type: Upgrade version

Origin: GHSA-q8mj-m7cp-5q26

Release Date: 2026-05-16

Fix Resolution: qs - 6.15.2,qs - 6.15.2,https://github.com/ljharb/qs.git - v6.15.2

CVE-2026-82417

Vulnerable Library - qs-6.14.1.tgz

A querystring parser that supports nesting and arrays, with a depth limit

Library home page: https://registry.npmjs.org/qs/-/qs-6.14.1.tgz

Sample Path to Dependency File: /package.json

Path to vulnerable library: /package.json

Dependency Hierarchy:

• express-5.2.1.tgz (Root Library)
  • ❌ qs-6.14.1.tgz (Vulnerable Library)

Found in base branch: main

Vulnerability Details

Summary
"qs.stringify" throws a "TypeError" when it serializes an object whose own "constructor" property has a truthy, non-callable "isBuffer" member. "utils.isBuffer" duck-types buffers by calling "obj.constructor.isBuffer(obj)" after checking only that the property is truthy, so a value such as "{ constructor: { isBuffer: "x" } }" makes the call throw "TypeError: obj.constructor.isBuffer is not a function".
Details
"lib/stringify.js:127" calls "utils.isBuffer" on every non-primitive value it serializes. "utils.isBuffer" ("lib/utils.js:332") reads "obj.constructor.isBuffer" and invokes it without verifying that it is a function. "constructor" and "isBuffer" are ordinary property names, so any object carrying them as own properties reaches the unchecked call.
Such an object can be built from untrusted input. "qs.parse("x[constructor][isBuffer]=y", { plainObjects: true })" or "{ allowPrototypes: true }" keeps the "constructor" key as an own property (the default parse options drop it), and "JSON.parse("{"a":{"constructor":{"isBuffer":"x"}}}")" produces the same shape with no qs option involved. Express 4 with its default "query parser" setting and body-parser with "extended: true" both call "qs.parse" with "allowPrototypes: true", so on those stacks "req.query" and "req.body" can carry the shape directly.
PoC
Fix
"lib/utils.js", applied in e83d321 on "main" and released as v6.16.0:
Real "Buffer", "safer-buffer", and browserify "buffer" polyfill instances serialize exactly as before; only the throw is removed.
Affected versions
">=2.2.5 <6.16.0", fixed in v6.16.0.
The unguarded duck-type was introduced in 3768a75 and first shipped in v2.2.5 (September 2014). v2.2.4 and earlier used "Buffer.isBuffer" and are not affected. Every release from v2.2.5 through v6.15.3 contains the unguarded call.
Impact
An unauthenticated request can make any code path that re-serializes attacker-influenced data with "qs.stringify" (for example, rebuilding a query string from "req.query" for a redirect or an upstream request, or serializing a parsed JSON body) throw synchronously. In a typical Node.js HTTP framework the throw is caught by the framework error boundary and the affected request returns a 500; the process survives and other requests are unaffected. Where the call runs outside an error boundary, such as an "async" Express 4 handler (where the throw becomes an unhandled promise rejection) or a background job, the process exits, so the impact in that case depends on the application error handling rather than on qs.
Mend Note: The description of this vulnerability differs from MITRE.

Publish Date: 2026-08-29

URL: CVE-2026-82417

CVSS 3 Score Details (5.3)

Base Score Metrics:

• Exploitability Metrics:
  • Attack Vector: Network
  • Attack Complexity: Low
  • Privileges Required: None
  • User Interaction: None
  • Scope: Unchanged
• Impact Metrics:
  • Confidentiality Impact: None
  • Integrity Impact: None
  • Availability Impact: Low

For more information on CVSS3 Scores, click here.

Suggested Fix

Type: Upgrade version

Origin: GHSA-4mjr-xmp4-gh2g

Release Date: 2026-08-29

Fix Resolution: qs - 6.16.0,qs - 6.16.0,https://github.com/ljharb/qs.git - v6.16.0

CVE-2026-2391

Vulnerable Library - qs-6.14.1.tgz

A querystring parser that supports nesting and arrays, with a depth limit

Library home page: https://registry.npmjs.org/qs/-/qs-6.14.1.tgz

Sample Path to Dependency File: /package.json

Path to vulnerable library: /package.json

Dependency Hierarchy:

• express-5.2.1.tgz (Root Library)
  • ❌ qs-6.14.1.tgz (Vulnerable Library)

Found in base branch: main

Vulnerability Details

Summary
The "arrayLimit" option in qs does not enforce limits for comma-separated values when "comma: true" is enabled, allowing attackers to cause denial-of-service via memory exhaustion. This is a bypass of the array limit enforcement, similar to the bracket notation bypass addressed in GHSA-6rw7-vpxm-498p (CVE-2025-15284).
Details
When the "comma" option is set to "true" (not the default, but configurable in applications), qs allows parsing comma-separated strings as arrays (e.g., "?param=a,b,c" becomes "['a', 'b', 'c']"). However, the limit check for "arrayLimit" (default: 20) and the optional throwOnLimitExceeded occur after the comma-handling logic in "parseArrayValue", enabling a bypass. This permits creation of arbitrarily large arrays from a single parameter, leading to excessive memory allocation.
Vulnerable code (lib/parse.js: lines ~40-50):
The "split(',')" returns the array immediately, skipping the subsequent limit check. Downstream merging via "utils.combine" does not prevent allocation, even if it marks overflows for sparse arrays.This discrepancy allows attackers to send a single parameter with millions of commas (e.g., "?param=,,,,,,,,..."), allocating massive arrays in memory without triggering limits. It bypasses the intent of "arrayLimit", which is enforced correctly for indexed ("a[0]=") and bracket ("a[]=") notations (the latter fixed in v6.14.1 per GHSA-6rw7-vpxm-498p).
PoC
Test 1 - Basic bypass:
Configuration:

• "comma: true"
• "arrayLimit: 5"
• "throwOnLimitExceeded: true"
  Expected: Throws "Array limit exceeded" error.
  Actual: Parses successfully, creating an array of length 26.
  Impact
  Denial of Service (DoS) via memory exhaustion.
  Mend Note: The description of this vulnerability differs from MITRE.

Publish Date: 2026-02-12

URL: CVE-2026-2391

CVSS 3 Score Details (3.7)

Base Score Metrics:

• Exploitability Metrics:
  • Attack Vector: Network
  • Attack Complexity: High
  • Privileges Required: None
  • User Interaction: None
  • Scope: Unchanged
• Impact Metrics:
  • Confidentiality Impact: None
  • Integrity Impact: None
  • Availability Impact: Low

For more information on CVSS3 Scores, click here.

Suggested Fix

Type: Upgrade version

Origin: GHSA-w7fw-mjwx-w883

Release Date: 2026-02-12

Fix Resolution: qs - 6.14.2,https://github.com/ljharb/qs.git - v6.14.2,qs - 6.14.2

CVE-2026-12590

Vulnerable Library - body-parser-2.2.2.tgz

Node.js body parsing middleware

Library home page: https://registry.npmjs.org/body-parser/-/body-parser-2.2.2.tgz

Sample Path to Dependency File: /package.json

Path to vulnerable library: /package.json

Dependency Hierarchy:

• express-5.2.1.tgz (Root Library)
  • ❌ body-parser-2.2.2.tgz (Vulnerable Library)

Found in base branch: main

Vulnerability Details

Impact: In body-parser versions prior to 1.20.6 (1.x line) and 2.3.0 (2.x line), when the parser is configured with an invalid limit option value such as an unparseable string or NaN, bytes.parse returns null and the request body size check is silently skipped. Applications that rely on limit as their primary safeguard against oversized request bodies will accept arbitrarily large payloads, leading to excessive memory and CPU usage and denial of service. Patches: This issue is fixed in body-parser 1.20.6 and 2.3.0. After the fix, invalid limit values throw a clear error at parser construction time instead of silently disabling enforcement, while null and undefined continue to fall back to the default limit of 100kb. Workarounds: Validate the limit value before passing it to body-parser. For example, parse the value at startup and reject any configuration where the result is null or a non-finite number.

Publish Date: 2026-07-09

URL: CVE-2026-12590

CVSS 3 Score Details (3.7)

Base Score Metrics:

• Exploitability Metrics:
  • Attack Vector: Network
  • Attack Complexity: High
  • Privileges Required: None
  • User Interaction: None
  • Scope: Unchanged
• Impact Metrics:
  • Confidentiality Impact: None
  • Integrity Impact: None
  • Availability Impact: Low

For more information on CVSS3 Scores, click here.

Suggested Fix

Type: Upgrade version

Origin: GHSA-v422-hmwv-36x6

Release Date: 2026-07-09

Fix Resolution: body-parser - 1.20.6,body-parser - 2.3.0