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.
Blast Radius
yt-dlpReal-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
During file downloads, yt-dlp or the external downloaders that yt-dlp employs may leak cookies on HTTP redirects to a different host, or leak them when the host for download fragments differs from their parent manifest's host.
This vulnerable behavior is present in all versions of youtube-dl, youtube-dlc and yt-dlp released since 2015.01.25. All native and external downloaders are affected, except for curl and httpie (httpie version 3.1.0 or later).
At the file download stage, all cookies are passed by yt-dlp to the file downloader as a Cookie header, thereby losing their scope. This also occurs in yt-dlp's info JSON output, which may be used by external tools. As a result, the downloader or external tool may indiscriminately send cookies with requests to domains or paths for which the cookies are not scoped.
An example of a potential attack scenario exploiting this vulnerability:
- an attacker has crafted a malicious website with an embedded URL designed to be detected by yt-dlp as a video download. This embedded URL has the domain of a trusted site that the user has loaded cookies for, and conducts an unvalidated redirect to a target URL.
- yt-dlp extracts this URL and calculates a
Cookieheader based on its domain for the file downloader to make its request(s) with. - the download URL redirects to a server controlled by the attacker, to which yt-dlp forwards the user's sensitive cookie information.
Patches
yt-dlp version 2023.07.06 fixes this issue by doing the following:
- Remove the
Cookieheader upon HTTP redirects - Have native downloaders calculate their own
Cookieheader from the cookiejar - Utilize external downloaders' built-in support for cookies instead of passing them as header arguments
- If the external downloader does not have proper cookie support, then disable HTTP redirection (
axelonly) - Process cookies passed as HTTP headers to limit their scope (
--add-header "Cookie:..."is scoped to input URL domain only) - Store cookies in a separate
cookiesfield of the info dict instead ofhttp_headersso as not to lose their scope
Patches for youtube-dl are expected and we will update this advisory when they are merged.
Workarounds
It is recommended to upgrade yt-dlp to version 2023.07.06 as soon as possible.
For users who are not able to upgrade:
- Avoid using cookies and user authentication methods (
--cookies,--cookies-from-browser,--username,--password,--netrc). While extractors may set custom cookies, these usually do not contain sensitive information. - Avoid using
--load-info-json
Or, if authentication is a must:
- Verify the integrity of download links from unknown sources in browser (including redirects) before passing them to yt-dlp
- Use
curlas external downloader, since it is not impacted (--downloader curl) - Avoid fragmented formats such as HLS/m3u8, DASH/mpd and ISM (use
-f "(bv*+ba/b)[protocol~='^https?$']")
References
- https://github.com/yt-dlp/yt-dlp/security/advisories/GHSA-v8mc-9377-rwjj
- https://nvd.nist.gov/vuln/detail/CVE-2023-35934
- https://github.com/yt-dlp/yt-dlp/releases/tag/2023.07.06
- https://github.com/yt-dlp/yt-dlp-nightly-builds/releases/tag/2023.07.06.185519
- https://github.com/yt-dlp/yt-dlp/commit/1ceb657bdd254ad961489e5060f2ccc7d556b729
- https://github.com/yt-dlp/yt-dlp/commit/f8b4bcc0a791274223723488bfbfc23ea3276641
- https://github.com/yt-dlp/yt-dlp/commit/3121512228487c9c690d3d39bfd2579addf96e07
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | yt-dlp | all versions | 2023.7.06 |
Detection & mitigation playbook
Open-source dependencyDetect
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.
Fix
Update yt-dlp to 2023.7.06 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-v8mc-9377-rwjj 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 pinpoints whether GHSA-v8mc-9377-rwjj 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-v8mc-9377-rwjj. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-v8mc-9377-rwjj in your dependencies?
O3 detects GHSA-v8mc-9377-rwjj across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.