T09 · Insecure Skill Coding Practices
- Location
scripts/fetch-rss-hot.js:22- Finding
Unbounded RSS Response Buffering Enables Denial of Service
- Content
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Vulnerability Details
File Location:
scripts/fetch-rss-hot.js, lines 22-28
Vulnerability Type: Unbounded remote response buffering
Risk Level: MediumVulnerable Code
js https.get(url, (res) => { let data = ''; res.on('data', chunk => data += chunk); res.on('end', () => resolve(data)); res.on('error', reject); }).on('error', reject);Technical Analysis
The RSS client accumulates the complete HTTPS response in an in-memory string without enforcing a maximum response size. It also does not configure connection or response timeouts, verify that the HTTP status is successful, or validate the response content type before buffering and parsing it.
Although the feed URL is statically configured, exploitation is possible if the configured service or an infrastructure component controlling its valid HTTPS response is compromised. A malicious or malfunctioning endpoint can return an extremely large body or continuously stream data without ending the response. Each chunk is appended to
data, causing memory consumption to grow until the process becomes unresponsive or is terminated.Attack Path
- An attacker compromises the configured RSS service or otherwise gains control over the content returned through its valid HTTPS endpoint.
- The Skill invokes
node scripts/fetch-rss-hot.js. - The endpoint returns a very large response or an indefinitely streamed body.
- The
dataevent handler continuously appends received chunks to the in-memory string. - Because no byte limit or timeout exists, the Node.js process exhausts memory or remains occupied indefinitely.
- The Skill run fails, and the hosting agent process may suffer degraded availability depending on process isolation.
Impact Assessment
The issue primarily affects availability. It does not directly grant filesystem privileges, command execution, credential access, or privilege escalation.
A successful exploit can exhaust memory allocated to the Node.js ...[truncated 317 chars]
- Remediation
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Remediation Suggestions
- Enforce a conservative maximum response size and destroy the request when the limit is exceeded.
- Configure connection and response timeouts so stalled or indefinitely streamed responses are terminated.
- Reject redirects unless they are explicitly required and constrained to trusted HTTPS hosts.
- Accept only successful HTTP status codes, such as
200. - Validate the response
Content-Typeagainst expected RSS/XML media types. - Check
Content-Lengthwhen present, while retaining streamed byte counting because that header can be absent or inaccurate. - Prefer incremental XML parsing rather than buffering the entire document.
- Run the script with process-level memory and execution-time limits as defense in depth.
- Return a controlled error when any limit is exceeded.
Example hardening pattern:
js function fetchXML(url) { const MAX_BYTES = 2 * 1024 * 1024; const TIMEOUT_MS = 10_000; return new Promise((resolve, reject) => { const req = https.get(url, (res) => { if (res.statusCode !== 200) { res.resume(); reject(new Error(`Unexpected HTTP status: ${res.statusCode}`)); return; } const contentType = res.headers['content-type'] || ''; if (!/(application|text)\/(rss\+xml|xml)/i.test(contentType)) { res.resume(); reject(new Error(`Unexpected content type: ${contentType}`)); return; } let bytes = 0; const chunks = []; res.on('data', (chunk) => { bytes += chunk.length; if (bytes > MAX_BYTES) { req.destroy(new Error('RSS response exceeds size limit')); return; } chunks.push(chunk); }); res.on('end', () => { resolve(Buffer.concat(chunks).toString('utf8')); }); res.on('error', reject); }); req.setTimeout(TIMEOUT_MS, () => { req.destroy(new Error('RSS request timed out')); }); req.on('error', reject); }); }