8.8

CVSS Score

3.1

-

CVSS Score

Basic Information

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CVE-2026-26331

CVE-2026-26331: yt-dlp: Arbitrary Command Injection when using the `--netrc-cmd` option

yt-dlp is a command-line audio/video downloader. Starting in version 2023.06.21 and prior to version 2026.02.21, when yt-dlp's --netrc-cmd command-line option (or netrc_cmd Python API parameter) is used, an attacker could achieve arbitrary command injection on the user's system with a maliciously crafted URL. yt-dlp maintainers assume the impact of this vulnerability to be high for anyone who uses --netrc-cmd in their command/configuration or netrc_cmd in their Python scripts. Even though the maliciously crafted URL itself will look very suspicious to many users, it would be trivial for a maliciously crafted webpage with an inconspicuous URL to covertly exploit this vulnerability via HTTP redirect. Users without --netrc-cmd in their arguments or netrc_cmd in their scripts are unaffected. No evidence has been found of this exploit being used in the wild. yt-dlp version 2026.02.21 fixes this issue by validating all netrc "machine" values and raising an error upon unexpected input. As a workaround, users who are unable to upgrade should avoid using the --netrc-cmd command-line option (or netrc_cmd Python API parameter), or they should at least not pass a placeholder ({}) in their --netrc-cmd argument.

(GitHub Advisory)

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CVE-2026-26331

CVE-2026-26331:

8.8

CVSS Score

3.1

-

CVSS Score

Basic Information

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Technical Details

Package Name	Ecosystem	Vulnerable Versions	First Patched Version
yt-dlp	pip	>= 2023.06.21, < 2026.02.21	2026.02.21

Technical Details

Vulnerability Intelligence
Miggo AI

Root Cause Analysis

The vulnerability is an OS command injection in yt-dlp that can be triggered when using the --netrc-cmd option with a specially crafted URL. The root cause of the vulnerability lies in the InfoExtractor._get_netrc_login_info function, which is responsible for handling the --netrc-cmd functionality. This function would construct and execute a shell command using the netrc_machine value, which is derived from the input URL. The vulnerability existed because this netrc_machine value was not sanitized, allowing shell metacharacters to be passed to the command, leading to arbitrary command execution.

The vulnerability was exploitable through several extractors that dynamically determine the netrc_machine from the URL's hostname. The advisory specifically mentions GetCourseRuIE, TeachableIE, and TeachableCourseIE. The _real_extract methods of these extractors used overly permissive regular expressions to parse the URL, which allowed malicious hostnames containing shell metacharacters to be extracted and passed to the vulnerable _get_netrc_login_info function.

The patch addresses the vulnerability at two levels. First, it adds strict validation to the _get_netrc_login_info function to ensure that the netrc_machine value only contains a safe set of characters. Second, it tightens the URL validation regular expressions in the affected extractors to prevent them from parsing malicious hostnames in the first place. This two-pronged approach effectively mitigates the command injection vulnerability.

Vulnerable functions

InfoExtractor._get_netrc_login_info

yt_dlp/extractor/common.py

This function is the core of the vulnerability. It is responsible for executing a shell command when the `--netrc-cmd` option is used. Before the patch, the `netrc_machine` parameter, which could be controlled by a malicious URL, was used directly in the shell command without proper validation. This allowed an attacker to inject arbitrary shell commands by crafting a URL with special characters in the hostname, which would then be passed as the `netrc_machine`.

GetCourseRuIE._real_extract

yt_dlp/extractor/getcourseru.py

The `_real_extract` method of the `GetCourseRuIE` extractor was vulnerable because it used a permissive regex (`_BASE_URL_RE`) to parse the URL. This allowed a malicious URL with shell metacharacters in the hostname to be considered valid. The hostname was then used as the `netrc_machine` value, leading to command injection in the `_get_netrc_login_info` function. The patch tightens the regex to only allow alphanumeric characters and hyphens in the hostname.

TeachableIE._real_extract

yt_dlp/extractor/teachable.py

The `_real_extract` method of the `TeachableIE` extractor was vulnerable because it used a permissive regex (`_VALID_URL`) to extract the site name (`site_t`) from the URL. This site name was then used as the `netrc_machine`. The old regex allowed any character except `/`, which made it possible to include shell metacharacters in the site name, leading to command injection. The patch restricts the allowed characters to alphanumeric characters, dots, and hyphens.

TeachableCourseIE._real_extract

yt_dlp/extractor/teachable.py

Similar to `TeachableIE`, the `_real_extract` method of `TeachableCourseIE` was vulnerable due to a permissive regex in `_VALID_URL`. This allowed a malicious site name to be extracted from the URL and used as the `netrc_machine`, which could then be used to inject commands. The patch fixes this by restricting the characters allowed in the site name.

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WAF Rule

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Reasoning

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