Update npm package `next` to v15.5.21 [SECURITY] by hash-worker[bot] · Pull Request #9108 · hashintel/hash

hash-worker · 2026-07-27T13:35:00Z

This PR contains the following updates:

Package	Change	Age	Confidence
next (source)	`15.5.18` → `15.5.21`

Next.js: Denial of Service in App Router using Server Actions

CVE-2026-64641 / GHSA-m99w-x7hq-7vfj

More information

Details

Impact

Crafted requests targeting Next.js applications using App Router with at least one Server Action can lead to excessive CPU usage blocking processing of further requests in the same process.

Workarounds

No workaround exists besides upgrading. Applications using Pages Router or not using Server Actions are not vulnerable.

Severity

CVSS Score: 8.2 / 10 (High)
Vector String: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

Next.js: Unauthenticated disclosure of internal Server Function endpoints

CVE-2026-64643 / GHSA-955p-x3mx-jcvp

More information

Details

Impact

In Next.js applications using App Router, Server Actions (use server) or use cache endpoints can be disclosed bypassing any authentication on the pages where these endpoints are usually used.

Server Action IDs can be disclosed to unauthenticated users via publicly served client artifacts (for example, static chunks containing action references).

Affected users are applications using App Router + Server Actions.

By itself, this disclosure is typically a recon/enumeration primitive; however, it can increase risk when combined with other weaknesses.

Workarounds

Never assume any authentication claims at the use cache or use server boundary. Always authenticate within the boundary.

Severity

CVSS Score: 6.3 / 10 (Medium)
Vector String: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

Next.js: Denial of Service in the Image Optimization API using SVGs

CVE-2026-64644 / GHSA-q8wf-6r8g-63ch

More information

Details

Impact

When self-hosting Next.js with the default image loader, the Image Optimization API can optimize remotely hosted images if configured (not enabled by default). If those images contain malicious content, they can cause CPU exhaustion in /_next/image endpoints.

If you are using config.images.remotePatterns, only the patterns in that array are impacted.
If you are using config.images.unoptimized: true, you are NOT impacted.
If you are using config.images.loader: 'custom', you are NOT impacted.
If you are using Vercel, you are NOT impacted.

Workarounds

If you cannot upgrade immediately, you can avoid the expensive work by setting config.experimental.imgOptSkipMetadata : true.

Severity

CVSS Score: 6.3 / 10 (Medium)
Vector String: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

Next.js: Server-Side Request Forgery in rewrites via attacker-controlled destination hostname

CVE-2026-64645 / GHSA-p9j2-gv94-2wf4

More information

Details

Impact

A rewrites() or redirects() rule that builds its external destination hostname from request-controlled input can be pointed at an arbitrary hostname, regardless of the rule's hostname suffix. For a rewrite, Next.js proxies the request to that arbitrary host and serves the response from the application's origin, leading to Server-Side Request forgery. A redirects() rule configured this way is vulnerable to an Open Redirect.

This affects any destination that puts a dynamic segment in the hostname, whether from the path:

// next.config.js
module.exports = {
  async rewrites() {
    return [
      {
        source: '/:tenant',
        destination: 'https://:tenant.api.example.com',
      },
    ]
  },
}

or from a has capture:

// next.config.js
module.exports = {
  async rewrites() {
    return [
      {
        source: '/',
        has: [{ type: 'query', key: 'region', value: '(?<region>.+)' }],
        destination: 'https://:region.api.example.com',
      },
    ]
  },
}

Workarounds

If you cannot upgrade immediately, do not build the hostname of an external rewrites() or redirects() destination from user-controlled input. If a dynamic subdomain is required, constrain the value to hostname-safe characters: value: '(?<region>[a-z0-9-]+)'.

Severity

CVSS Score: 8.3 / 10 (High)
Vector String: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:L/VA:N/SC:L/SI:L/SA:N

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

Next.js: Unbounded Server Action payload in Edge runtime

CVE-2026-64646 / GHSA-4c39-4ccg-62r3

More information

Details

Impact

Requests targeting Next.js applications using App Router with at least one Server Action can lead to excessive memory consumption if that Server Actions uses the Edge runtime

Workarounds

If you cannot upgrade, ensure your hosting provider limits the request's body size. 5 MiB should be allowed at max by your hosting provider.

Severity

CVSS Score: 6.3 / 10 (Medium)
Vector String: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

Next.js: Cache confusion of response bodies for requests with bodies containing invalid UTF-8 byte sequences

CVE-2026-64647 / GHSA-4633-3j49-mh5q

More information

Details

Impact

A server-side fetch with a request body may return a cached response body from a different request to the same URL but different body. Confidential data in the POST's response body would then leak to unauthorized requests. Though the request itself will not be deduped.

This is only an issue when receiving request bodies with a content type charset other than UTF-8. For example, the UTF-16 byte sequences for 삃삃 and 섄섄 in the request body would share the same cache.

Workarounds

If you cannot upgrade, consider only making fetch requests with UTF-8 bodies (default in Next.js). Applications using Pages Router are not vulnerable.

Severity

CVSS Score: 6.3 / 10 (Medium)
Vector String: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

Next.js: Cache confusion of response bodies for requests with bodies

CVE-2026-64648 / GHSA-68g3-v927-f742

More information

Details

Impact

A server-side fetch with a request body may return a cached response body from a different request to the same URL but different body. Confidential data in the POST's response body would then leak to unauthorized requests. Though the request itself will not be deduped.

This only applies to fetch calls with a request that has a different init than the one passed to fetch.
Safe: fetch(new Request(init), init)
Unsafe: fetch(new Request(init), aDifferentInit)

Workarounds

No workaround exists besides upgrading. Applications using Pages Router are not vulnerable.

Severity

CVSS Score: 6.0 / 10 (Medium)
Vector String: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

Next.js: Server-Side Request Forgery in Server Actions on custom servers

CVE-2026-64649 / GHSA-89xv-2m56-2m9x

More information

Details

Impact

When a Server Action forwards or redirects a request, an attacker can cause the server to send that outbound request to a malicious host (Server-Side Request Forgery). This requires the attacker's request to control Host-associated headers. In some configurations, it's also possible to obtain internal values that weaken middleware/proxy authorization.

Applications that use Server Actions are affected when the incoming host header is not fixed to a trusted value. This typically occurs on custom servers, or on deployments not behind a proxy that pins the host. Managed hosting pins the host upstream and is not affected; next start and standalone output do the same from version 14.2 onward.

Workarounds

If you cannot upgrade, ensure clients do not control the host header your application receives. Pin or validate Host and X-Forwarded-Host at your edge or proxy. On version 14.2.0 and later, you can additionally set the __NEXT_PRIVATE_ORIGIN environment variable to your deployment's real origin:

__NEXT_PRIVATE_ORIGIN=https://www.example.com node server.js

#### Severity
- CVSS Score: 8.3 / 10 (High)
- Vector String: `CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N`

#### References
- [https://github.com/vercel/next.js/security/advisories/GHSA-89xv-2m56-2m9x](https://redirect.github.com/vercel/next.js/security/advisories/GHSA-89xv-2m56-2m9x)
- [https://github.com/vercel/next.js/commit/b51206321854193208c0805ba42acc49287f942b](https://redirect.github.com/vercel/next.js/commit/b51206321854193208c0805ba42acc49287f942b)
- [https://github.com/vercel/next.js/commit/e3e5666ccead3a15162793d697af5e48b7cc0498](https://redirect.github.com/vercel/next.js/commit/e3e5666ccead3a15162793d697af5e48b7cc0498)
- [https://github.com/vercel/next.js/releases/tag/v15.5.21](https://redirect.github.com/vercel/next.js/releases/tag/v15.5.21)
- [https://github.com/vercel/next.js/releases/tag/v16.2.11](https://redirect.github.com/vercel/next.js/releases/tag/v16.2.11)
- [https://github.com/advisories/GHSA-89xv-2m56-2m9x](https://redirect.github.com/advisories/GHSA-89xv-2m56-2m9x)

This data is provided by the [GitHub Advisory Database](https://redirect.github.com/advisories/GHSA-89xv-2m56-2m9x) ([CC-BY 4.0](https://redirect.github.com/github/advisory-database/blob/main/LICENSE.md)).
</details>

---

### Release Notes

<details>
<summary>vercel/next.js (next)</summary>

### [`v15.5.21`](https://redirect.github.com/vercel/next.js/releases/tag/v15.5.21)

[Compare Source](https://redirect.github.com/vercel/next.js/compare/v15.5.20...v15.5.21)

This release contains security fixes for the following advisories:

High:

- [Denial of Service in App Router using Server Actions](https://redirect.github.com/vercel/next.js/security/advisories/GHSA-m99w-x7hq-7vfj)
- [Middleware / Proxy bypass in App Router applications using Turbopack and single locale](https://redirect.github.com/vercel/next.js/security/advisories/GHSA-6gpp-xcg3-4w24)
- [Server-Side Request Forgery in rewrites via attacker-controlled destination hostname](https://redirect.github.com/vercel/next.js/security/advisories/GHSA-p9j2-gv94-2wf4)
- [Server-Side Request Forgery in Server Actions on custom servers](https://redirect.github.com/vercel/next.js/security/advisories/GHSA-89xv-2m56-2m9x)

Moderate:

- [Cache confusion of response bodies for requests with bodies](https://redirect.github.com/vercel/next.js/security/advisories/GHSA-68g3-v927-f742)
- [Cache confusion of response bodies for requests with bodies containing invalid UTF-8 byte sequences](https://redirect.github.com/vercel/next.js/security/advisories/GHSA-4633-3j49-mh5q)
- [Denial of Service in the Image Optimization API using SVGs](https://redirect.github.com/vercel/next.js/security/advisories/GHSA-q8wf-6r8g-63ch)
- [Unauthenticated disclosure of internal Server Function endpoints](https://redirect.github.com/vercel/next.js/security/advisories/GHSA-955p-x3mx-jcvp)
- [Unbounded Server Action payload in Edge runtime](https://redirect.github.com/vercel/next.js/security/advisories/GHSA-4c39-4ccg-62r3)

### [`v15.5.20`](https://redirect.github.com/vercel/next.js/releases/tag/v15.5.20)

[Compare Source](https://redirect.github.com/vercel/next.js/compare/v15.5.19...v15.5.20)

Contains no changes except publishing `@next/swc-wasm-web` which was accidentally not published since 15.5.15.

### [`v15.5.19`](https://redirect.github.com/vercel/next.js/releases/tag/v15.5.19): 15.5.19

[Compare Source](https://redirect.github.com/vercel/next.js/compare/v15.5.18...v15.5.19)

> \[!NOTE]
> This release is backporting bug fixes. It does **not** include all pending features/changes on canary.

##### Core Changes

- \[15.5.x] Don't drop `FormData` entries ([#&#8203;94244](https://redirect.github.com/vercel/next.js/issues/94244))

##### Other

- \[15.5.x] Fix CI ([#&#8203;94281](https://redirect.github.com/vercel/next.js/issues/94281))

##### Credits

Huge thanks to [@&#8203;eps1lon](https://redirect.github.com/eps1lon) for helping!

</details>

---

### Configuration

📅 **Schedule**: (UTC)

- Branch creation
  - At any time (no schedule defined)
- Automerge
  - "before 4am every weekday,every weekend"

🚦 **Automerge**: Enabled.

♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 **Ignore**: Close this PR and you won't be reminded about these updates again.

---

 - [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check this box

---

This PR has been generated by [Mend Renovate](https://redirect.github.com/renovatebot/renovate).
<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiI0My4yNDMuMiIsInVwZGF0ZWRJblZlciI6IjQzLjI0My4yIiwidGFyZ2V0QnJhbmNoIjoibWFpbiIsImxhYmVscyI6W119-->

hash-worker · 2026-07-27T13:35:04Z

⚠️ Artifact update problem

Renovate failed to update an artifact related to this branch. You probably do not want to merge this PR as-is.

♻ Renovate will retry this branch, including artifacts, only when one of the following happens:

any of the package files in this branch needs updating, or
the branch becomes conflicted, or
you click the rebase/retry checkbox if found above, or
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The artifact failure details are included below:

File name: yarn.lock

error This project's package.json defines "packageManager": "yarn@4.16.0". However the current global version of Yarn is 1.22.22.

Presence of the "packageManager" field indicates that the project is meant to be used with Corepack, a tool included by default with all official Node.js distributions starting from 16.9 and 14.19.
Corepack must currently be enabled by running corepack enable in your terminal. For more information, check out https://yarnpkg.com/corepack.

vercel · 2026-07-27T13:35:06Z

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated (UTC)
hash	Error		Jul 27, 2026 1:40pm

2 Skipped Deployments

Project	Deployment	Actions	Updated (UTC)
hashdotdesign-tokens	Ignored		Jul 27, 2026 1:40pm
petrinaut	Skipped		Jul 27, 2026 1:40pm

cursor · 2026-07-27T13:35:09Z

PR Summary

Low Risk
Dependency-only security patch with no app logic changes; main risk is standard framework upgrade regression testing on the Next.js frontend.

Overview
Bumps the next dependency from 15.5.18 to 15.5.21 in apps/hash-frontend (runtime) and libs/@local/hash-isomorphic-utils (dev dependency). No application source changes—only the pinned framework version.

This patch release addresses multiple Next.js security advisories (Server Actions DoS/SSRF, rewrite/redirect hostname SSRF, fetch response cache confusion, image optimization DoS, Server Function endpoint disclosure, and related issues).

^{Reviewed by Cursor Bugbot for commit 09c4493. Bugbot is set up for automated code reviews on this repo. Configure here.}

Update npm package next to v15.5.21 [SECURITY]

09c4493

hash-worker Bot enabled auto-merge July 27, 2026 13:35

hash-worker Bot assigned CiaranMn Jul 27, 2026

vercel Bot had a problem deploying to Preview – hash July 27, 2026 13:40 Failure

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Update npm package `next` to v15.5.21 [SECURITY] - #9108

Update npm package `next` to v15.5.21 [SECURITY]#9108
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Next.js: Denial of Service in App Router using Server Actions

Details

Impact

Workarounds

Severity

References

Next.js: Unauthenticated disclosure of internal Server Function endpoints

Details

Impact

Workarounds

Severity

References

Next.js: Denial of Service in the Image Optimization API using SVGs

Details

Impact

Workarounds

Severity

References

Next.js: Server-Side Request Forgery in rewrites via attacker-controlled destination hostname

Details

Impact

Workarounds

Severity

References

Next.js: Unbounded Server Action payload in Edge runtime

Details

Impact

Workarounds

Severity

References

Next.js: Cache confusion of response bodies for requests with bodies containing invalid UTF-8 byte sequences

Details

Impact

Workarounds

Severity

References

Next.js: Cache confusion of response bodies for requests with bodies

Details

Impact

Workarounds

Severity

References

Next.js: Server-Side Request Forgery in Server Actions on custom servers

Details

Impact

Workarounds

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hash-worker Bot commented Jul 27, 2026

⚠️ Artifact update problem

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