KEVWire

Security intelligence, with context.

Response snapshot Oct 26, 2026, 22:09 UTC

Back to the wire
Permalink
VulnerabilityCVE-2026-111756

follow-redirects array-form headers bypass cross-origin credential stripping

```js function removeMatchingHeaders(regex, headers) { var lastValue; for (var header in headers) { // for...in over an ARRAY yields "0","1","2"... if (regex.

Published Updated

At a glance

Exploited
Not known
Severity
8.2 High (CVSS 4.0)
Chance of exploitation
0.5% in the next 30 days
Sources
2 independent sources

What to do

GitHub lists first patched versions: follow-redirects: 1.16.1. Confirm the affected range and upgrade guidance in the exact advisory.

Read GitHub-reviewed advisory GHSA-q3jh-wrc6-jgq8 (opens a new tab)

What happened

### Summary follow-redirects removes sensitive credential headers (Authorization, Proxy-Authorization, Cookie, and any caller-declared `sensitiveHeaders`) before following a redirect that crosses to a different host or downgrades to a less secure protocol. The removal routine iterates the caller's headers container with `for...in` and matches header names against a filter.

This assumes the headers container is a plain object keyed by header names. Node's underlying `http.request`, which follow-redirects is a drop-in replacement for, also accepts headers as an alternating array of names and values. For an array, `for...in` yields the numeric indices `"0"`, `"1"`, `"2"` and so on, which never match a header-name filter, so nothing is removed.

An application that sends array-form headers and follows an attacker-controlled cross-origin redirect therefore forwards its Authorization, Cookie, and Proxy-Authorization headers verbatim to the attacker-controlled destination, with no error or warning. The `sensitiveHeaders` option added to fix CVE-2026-40895 / GHSA-r4q5-vmmm-2653 is equally ineffective, because it relies on the same helper.

This is an unauthenticated confidentiality vulnerability: any remote server the victim application contacts can harvest the victim's credential headers by responding with a cross-origin redirect.

Continue reading

### Details The cross-origin credential-stripping control is implemented by `removeMatchingHeaders(regex, headers)` at `index.js:630-640`:

```js function removeMatchingHeaders(regex, headers) { var lastValue; for (var header in headers) { // for...in over an ARRAY yields "0","1","2"... if (regex.test(header)) { // the header-name filter never matches a numeric index lastValue = headers[header]; delete headers[header]; } } return (lastValue === null || typeof lastValue === "undefined") ? undefined : String(lastValue).trim(); } ```

It is invoked from `_processResponse` for three purposes, all with the caller-supplied `this._options.headers`:

- `index.js:490` - strip the credential filter (`this._headerFilter`, which covers the built-in list Authorization/Proxy-Authorization/Cookie plus any `sensitiveHeaders`) when the redirect crosses origin or downgrades protocol. - `index.js:470` - strip the `Host` header (`/^host$/i`). - `index.js:466` - strip `content-*` headers when a 301/302/303 converts POST to GET.

The caller-supplied headers container is passed straight through to each redirected request via `nativeProtocol.request(this._options)` at `index.js:352`. `_sanitizeOptions` (index.js:300-331) only replaces `options.headers` when it is falsy, so an array is left untouched.

Node's `http.request` accepts `options.headers` as an alternating array of names and values (for example `["Authorization", "Bearer ...", "Cookie", "session=..."]`). This is a supported way to control header ordering and duplication.

For such an array, `for (var header in headers)` iterates the numeric indices `"0"`, `"1"`, `"2"`, and the header-name regex never matches any of them, so `removeMatchingHeaders` deletes nothing. Every one of the three strip operations above silently no-ops:

- The built-in credential headers (Authorization, Cookie, Proxy-Authorization) are forwarded to the cross-origin redirect target. - Any `sensitiveHeaders` the caller declared are forwarded too. - The stale `Host` of the previous origin is re-sent to the new origin. - On a POST-to-GET redirect the `content-*` headers are retained, leaving `Content-Length` inconsistent with the now-empty body.

The primary and highest-impact consequence is disclosure of credential headers. The stale `Host` re-send and the `Content-Length` inconsistency are secondary correctness defects arising from the same root cause.

Root-cause history: the `for...in`-based `removeMatchingHeaders` used for the built-in credential strip has been present since the cross-host Authorization drop was introduced (commit `724087d`, first released in v1.11.0) and is unchanged through 1.16.0. The `sensitiveHeaders` layer was introduced in 1.16.0 (commit `844c4d3`). The behavior was verified directly on both 1.15.11 and 1.16.0.

Suggested remediation: handle or explicitly reject Node's array-form headers. The strictest fix is to detect `Array.isArray(options.headers)` in `_sanitizeOptions` and throw a clear `TypeError` instructing callers to pass an object, so misuse fails loudly instead of silently downgrading security. If array support is desired, extend `removeMatchingHeaders` to walk the array in name/value pairs:

```js function removeMatchingHeaders(regex, headers) { if (Array.isArray(headers)) { var lastValue; for (var i = 0; i r.end(JSON.stringify(q.headers)));s.listen(0,"127.0.0.1",()=>{var p=s.address().port;http.request({hostname:"127.0.0.1",port:p,headers:["Authorization","Bearer T","Cookie","c=1"]},res=>{var b="";res.on("data",c=>b+=c);res.on("end",()=>{console.log(JSON.parse(b).authorization, JSON.parse(b).cookie);s.

close();});}).end();});' ``` Observed: `Bearer T c=1` (the server receives both headers, confirming array form is valid and delivered).

Minimal form (built-in credential list), `arrayleak.js`: ```js var followRedirects = require("./index.js"); var http = require("http"); var redirector = http.createServer(function (req, res) { req.resume(); res.writeHead(302, { Location: "http://127.0.0.1:47302/steal" }); // cross-origin (different port) res.end(); }); var collector = http.createServer(function (req, res) { res.end(JSON.stringify(req.

headers)); // attacker-controlled target }); redirector.listen(47301, "127.0.0.1", function () { collector.listen(47302, "127.0.0.1", function () { followRedirects.http.request({ hostname: "127.0.0.1", port: 47301, path: "/", method: "GET", headers: [ "Host", "127.0.0.

1:47301", "Authorization", "Bearer ARRAY-FORM-VICTIM-TOKEN", "Cookie", "session=ARRAY-FORM-SESSION-ID", "X-Custom", "harmless" ] }, function (res) { var body = ""; res.on("data", function (c) { body += c; }

Affected package ranges reported by GitHub: follow-redirects: >= 1.16.0, < 1.16.1

Scores and how they were measured

CVSS base severity

8.2

Version 4.0As of

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

0.5%

Scored Percentile 40.5%

Model and measurement source (opens a new tab)

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

Sources

  1. Primary source

    GitHub-reviewed advisory GHSA-q3jh-wrc6-jgq8 (opens a new tab)

    The public advisory supplies the description, affected package/version ranges, and any listed CVSS metric. GitHub review is not local review.

    Published Checked

  2. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-q3jh-wrc6-jgq8, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  3. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-q3jh-wrc6-jgq8, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  4. Primary source

    NVD CVE-2026-111756 (opens a new tab)

    NVD record: description, CVSS (the CNA score is preferred), affected products, and publication date. Not evidence of exploitation.

    Published Checked

  5. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  6. Primary source

    FIRST measured EPSS score (opens a new tab)

    Measured EPSS probability and percentile for CVE-2026-111756, scored 2026-10-26. This is a model estimate, not proof of exposure.

    Published Checked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 23). follow-redirects array-form headers bypass cross-origin credential stripping (CVE-2026-111756). https://kevwire.com/record/CVE-2026-111756

MLA

"follow-redirects array-form headers bypass cross-origin credential stripping (CVE-2026-111756)." KEVWire, 23 Oct. 2026, kevwire.com/record/CVE-2026-111756.

Chicago

KEVWire. "follow-redirects array-form headers bypass cross-origin credential stripping (CVE-2026-111756)." Last modified October 23, 2026. https://kevwire.com/record/CVE-2026-111756.

Evidence summary (plain text)

follow-redirects array-form headers bypass cross-origin credential stripping (Oct 20, 2026).
```js
function removeMatchingHeaders(regex, headers) {
 var lastValue;
 for (var header in headers) { // for...in over an ARRAY yields "0","1","2"...
 if (regex.test(header)) { // the header-name filter never matches a numeric index
 lastValue = headers[header];
 delete headers[header];
 }
 }
 return (lastValue === null || typeof lastValue === "undefined") ?
 undefined : String(lastValue).trim();
}
```

It is invoked from `_processResponse` for three purposes, all with the caller-supplied `this._options.headers`:
CVSS 8.2 (version 4.0; evidence as of Oct 23, 2026; https://nvd.nist.gov/vuln/detail/CVE-2026-111756).
EPSS 0.5% for the following 30 days, scored Oct 26, 2026 (https://api.first.org/data/v1/epss?cve=CVE-2026-111756&date=2026-10-26).
Sources:
GitHub-reviewed advisory GHSA-q3jh-wrc6-jgq8: https://github.com/advisories/GHSA-q3jh-wrc6-jgq8
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMVQyMDozMDoyNlrOAAfvxw%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMVQyMDowMzo1N1rOAAfvxQ%3D%3D
NVD CVE-2026-111756: https://nvd.nist.gov/vuln/detail/CVE-2026-111756
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?pubStartDate=2026-10-12T13:35:55.142Z&pubEndDate=2026-10-26T13:35:55.142Z&resultsPerPage=500&startIndex=6000
FIRST measured EPSS score: https://api.first.org/data/v1/epss?cve=CVE-2026-111756&date=2026-10-26
Record ID: CVE-2026-111756.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 26, 2026, 19:40 UTC. Ingestion is not an independent editorial investigation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

Record JSON

Your account

Email alerts

Email alerts are not available yet. To follow your stack today, use its RSS feed, which honors your filters, or connect an AI agent through the API.

Suggest an improvement

Ideas, missing sources, corrections, and bugs are all welcome. No account needed. Suggestions are reviewed by a person before anything changes.

Record details

Record detail