MediumCVE-2026-116689

Follow-redirects: Insertion of Sensitive Information Into Sent Data (CVE-2026-116689)

Published 27.10.2026Last modified 30.10.2026Sources: OSV, Hersteller, CVE.org

What is affected, what to do

Update follow-redirects to version 1.16.2.

Affected: Follow-redirects gte 1.16.0, < 1.16.2..*

Not sure whether and how you are affected? Ask a question about this vulnerability

Metrics

5.9

Priority

XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

Source: Vendor (CNA), CVSS v3

5.9

CVSS v3

Severity Medium on the scale from 0 to 10.

Source: OSV, Hersteller, CVE.org

0.3 %

EPSS score

Low — model estimates < 1% exploitation likelihood.

Source: FIRST EPSS, percentile 18.8

Show all metrics

Severity: Medium
Priority (0–325) The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first? Read in glossary: 62.33 Methodology
Exploit maturity An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack. Read in glossary: no public PoC known
XIEM Effective CVSS XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command. Read in glossary: 5.9 Methodology
CVSS v3 CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions. Read in glossary: 5.9
EPSS score The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“. Read in glossary: 0.3 %; Low — model estimates < 1% exploitation likelihood.
EPSS percentile The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking. Read in glossary: 18.8; Elevated — this CVE ranks above at least 10% of all CVEs scored today.
KEV status The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching. Read in glossary: —
Published: 27.10.2026
CISA assessment (SSVC): Exploitation: proof of concept · not automatable · Technical impact: partial; Source: CISA Vulnrichment, as of 30 October 2026
CWE CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect. Read in glossary: CWE-201

Detection rules

No NEOSEC detection rule is available for this vulnerability yet.

Classification under NIS2 and CRA

Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

NIS2 NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management. Read in glossary: Handle the vulnerability in regular vulnerability handling under Art. 21(2)(e) NIS2.
CRA The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates. Read in glossary: From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
ISO/IEC 27001 ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security. Read in glossary: Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

Description

Summary

follow-redirects 1.16.0 and 1.16.1 validate the documented sensitiveHeaders option with instanceof Array. An array created in another JavaScript realm is silently replaced with an empty list, so a caller-declared custom credential header can be forwarded to an attacker-controlled cross-origin redirect destination.

Details

Affected versions

The sensitiveHeaders option was introduced in 1.16.0. Published 1.16.0 and 1.16.1 both reproduced, giving a tested affected range of 1.16.0 through 1.16.1. The source checkout was pinned at revision 46301256333c90b7faac7aa126effe72ec16d16e; the exact npm 1.16.1 artifact reproduced independently.

Root cause

index.js resets options.sensitiveHeaders when its local isArray() helper returns false. That helper uses value instanceof Array, which depends on realm identity. The same file already uses Array.isArray(options.headers), which correctly recognizes arrays across realms.

Suggested remediation

Use Array.isArray(value) for sensitiveHeaders, then validate and normalize each member as a header-name string. Add same-realm and node:vm cross-realm tests for cross-origin redirects, including the array-form headers representation. Verify that custom sensitive names are removed while unrelated headers remain unchanged.

Duplicate review

The public advisory history contains other sensitive-header findings, including array-form headers and regular-expression handling, but focused repository searches found no report describing cross-realm validation as of 2026-10-25. A private or differently worded report may already exist.

Proof of concept

Start two loopback HTTP servers. The first returns a 302 redirect to the second. Send X-API-Key and list that name in sensitiveHeaders, then compare a normal array with a genuine cross-realm array created by:

const vm = require('node:vm');
const sensitiveHeaders = vm.runInNewContext(`['X-API-Key']`);

Observed against both source and the exact npm 1.16.1 package:

Same-realm ['X-API-Key']: the redirect target did not receive the key.
Cross-realm ['X-API-Key']: Array.isArray(value) was true, value instanceof Array was false, and the redirect target received X-API-Key.
An unrelated X-Harmless header remained present in both cases.

The complete 3.5 KB loopback-only harness and raw JSON output are available privately.

Impact

custom credential disclosure. Exploitation requires a direct caller or wrapper that preserves a cross-realm sensitiveHeaders array, a custom credential listed in that option, and an attacker-controlled or compromised endpoint that returns a cross-origin redirect. The directly demonstrated result is disclosure of the custom header value, potentially exposing an API key or service token until revocation.

Built-in Authorization, Proxy-Authorization, and Cookie protections remained effective. Exact Axios 1.20.0 with follow-redirects 1.16.1 did not reproduce because Axios normalized the array; this report does not claim that Axios is affected. No third-party service was tested.

Source: OSV (Open Source Vulnerabilities), GitHub Security Advisories, cvelistv5, NVD (NIST)

Affected products

The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

Affected products
		Affected versions	Fixed in
follow-redirects	follow-redirects	`≥ 1.16.0, < 1.16.2`	—
npm	follow-redirects	`>= 1.16.0, <= 1.16.1` `1.16.0`	`1.16.2` `1.16.2`

Vendors and products

Follow-redirects Follow-redirects

Weakness classes (CWE)

CWE-201Insertion of Sensitive Information Into Sent Data
Base
The code transmits data to another actor, but a portion of the data includes sensitive information that should not be accessible to that actor.
Entry at MITRE CWE-201

References & sources

github.comfollow-redirects/follow-redirects/commit/b0a7751e9cd64cd8eeb6ec…x_refsource_MISC, web
github.comfollow-redirects/follow-redirects/releases/tag/v1.16.2x_refsource_MISC, web
github.comfollow-redirects/follow-redirects/security/advisories/GHSA-mrwp…x_refsource_CONFIRM, web
NVD (NIST)vuln/detail/CVE-2026-116689advisory
github.comfollow-redirects/follow-redirectspackage

Changes to this CVE

Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

30.10.2026Record modifiedCISA ADP

CISA assessment (SSVC): exploitation: proof of concept, automatable: no

New references:

https://github.com/follow-redirects/follow-redirects/security/advisories/GHSA-mrwp-f3q8-3g9p

Show 2 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
Reference	added	—	https://github.com/follow-redirects/follow-redirects/security/advisories/GHSA-mrwp-f3q8-3g9p
SSVC assessment	added	—	{"id":"CVE-2026-116689","role":"CISA Coordinator","options":[{"exploitation":"poc"},{"automatable":"no"},{"technicalImpact":"partial"}],"version":"2.0.3","timestamp":"2026-10-30T18:47:47.826619Z"}

Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

27.10.2026ReceivedGitHub

CVSS V3.1: AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

Weakness type: CWE-201

Description added or changed

New references:

Show 7 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
Description	added	—	follow-redirects is a Node.js HTTP and HTTPS client wrapper that automatically follows redirects. From 1.16.0 until 1.16.2, the documented sensitiveHeaders option is checked with value instanceof Array, so an array created in another JavaScript realm is replaced with an empty list even though Array.isArray recognizes it. When a request then follows an attacker-controlled cross-origin redirect, a custom credential header named in that discarded list can be forwarded to the redirect destination. This issue is fixed in version 1.16.2.
CVSS	added	—	AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
Weakness type (CWE)	added	—	CWE-201
Affected versions (publisher)	added	—	New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/116xxx/CVE-2026-116689.json">CVE-2026-116689</a>
Reference	added	—	https://github.com/follow-redirects/follow-redirects/commit/b0a7751e9cd64cd8eeb6ec67d2f206a9cc88d3f8
Reference	added	—	https://github.com/follow-redirects/follow-redirects/releases/tag/v1.16.2
Reference	added	—	https://github.com/follow-redirects/follow-redirects/security/advisories/GHSA-mrwp-f3q8-3g9p

Source identifier: security-advisories@github.com

Embed badge

Show the severity and KEV status of this vulnerability on your site – with a link back here. The image is updated hourly.

<a href="https://intel.neosec.eu/en/cve/CVE-2026-116689"><img src="https://intel.neosec.eu/badge/cve/CVE-2026-116689.svg?lang=en" alt="CVE-2026-116689 – NEOSEC Intel" height="20"></a>