GHSA-3G8H-86W9-WVMQ
Vulnerability from github – Published: 2026-05-11 16:12 – Updated: 2026-05-14 20:35Impact
Next.js uses the x-nextjs-data request header for internal data requests. On affected versions, an external client could send this header on a normal request to a path handled by middleware that returns a redirect.
When that happened, the middleware/proxy could treat the request as a data request and replace the standard Location redirect header with the internal x-nextjs-redirect header. Browsers do not follow x-nextjs-redirect, so the response became an unusable redirect for normal clients.
If the application was deployed behind a CDN or reverse proxy that caches 3xx responses without varying on this header, a single attacker request could poison the cached redirect response for the affected path. Subsequent visitors could then receive a cached redirect response without a Location header, causing a denial of service for that redirect path until the cache entry expired or was purged.
Affected scenarios
This affects applications that: - use middleware or proxy redirects - are deployed behind a caching CDN or reverse proxy - allow 3xx responses on those paths to be cached without differentiating internal data requests from normal requests
Fix
The fix stops trusting x-nextjs-data by itself for middleware redirect handling. A request is now treated as an internal data request only when it is validated as such by internal routing state, preserving legitimate data-request redirect behavior while preventing external header injection from changing normal redirect responses.
Workarounds
Before upgrading, users can reduce risk by:
- configuring the CDN or reverse proxy to vary its cache key on x-nextjs-data for affected responses
{
"affected": [
{
"package": {
"ecosystem": "npm",
"name": "next"
},
"ranges": [
{
"events": [
{
"introduced": "12.2.0"
},
{
"fixed": "15.5.16"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "npm",
"name": "next"
},
"ranges": [
{
"events": [
{
"introduced": "16.0.0"
},
{
"fixed": "16.2.5"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-44572"
],
"database_specific": {
"cwe_ids": [
"CWE-349"
],
"github_reviewed": true,
"github_reviewed_at": "2026-05-11T16:12:07Z",
"nvd_published_at": "2026-05-13T16:16:58Z",
"severity": "LOW"
},
"details": "### Impact\n\nNext.js uses the `x-nextjs-data` request header for internal data requests. On affected versions, an external client could send this header on a normal request to a path handled by middleware that returns a redirect.\n\nWhen that happened, the middleware/proxy could treat the request as a data request and replace the standard `Location` redirect header with the internal `x-nextjs-redirect` header. Browsers do not follow `x-nextjs-redirect`, so the response became an unusable redirect for normal clients.\n\nIf the application was deployed behind a CDN or reverse proxy that caches 3xx responses without varying on this header, a single attacker request could poison the cached redirect response for the affected path. Subsequent visitors could then receive a cached redirect response without a `Location` header, causing a denial of service for that redirect path until the cache entry expired or was purged.\n\n### Affected scenarios\n\nThis affects applications that:\n- use middleware or proxy redirects\n- are deployed behind a caching CDN or reverse proxy\n- allow 3xx responses on those paths to be cached without differentiating internal data requests from normal requests\n\n### Fix\n\nThe fix stops trusting `x-nextjs-data` by itself for middleware redirect handling. A request is now treated as an internal data request only when it is validated as such by internal routing state, preserving legitimate data-request redirect behavior while preventing external header injection from changing normal redirect responses.\n\n### Workarounds\n\nBefore upgrading, users can reduce risk by:\n- configuring the CDN or reverse proxy to vary its cache key on `x-nextjs-data` for affected responses",
"id": "GHSA-3g8h-86w9-wvmq",
"modified": "2026-05-14T20:35:56Z",
"published": "2026-05-11T16:12:07Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/vercel/next.js/security/advisories/GHSA-3g8h-86w9-wvmq"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-44572"
},
{
"type": "PACKAGE",
"url": "https://github.com/vercel/next.js"
},
{
"type": "WEB",
"url": "https://github.com/vercel/next.js/releases/tag/v15.5.16"
},
{
"type": "WEB",
"url": "https://github.com/vercel/next.js/releases/tag/v16.2.5"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L",
"type": "CVSS_V3"
}
],
"summary": "Next.js\u0027s Middleware / Proxy redirects can be cache-poisoned"
}
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