.NET and Visual Studio Remote Code Execution Vulnerability

.NET and Visual Studio Denial of Service Vulnerability

.NET and Visual Studio Denial of Service Vulnerability

Description The Git credential protocol is text-based over standard input/output, and consists of a series of lines of key-value pairs in the format key=value. Git's documentation restricts the use of the NUL (\0) character and newlines to form part of the keys[^1] or values.

When Git reads from standard input, it considers both LF and CRLF[^2] as newline characters for the credential protocol by virtue of calling strbufgetline that calls to strbufgetdelimstripcrlf. Git also validates that a newline is not present in the value by checking for the presence of the line-feed character (LF, \n), and errors if this is the case. This captures both LF and CRLF-type newlines.

Git Credential Manager uses the .NET standard library StreamReader class to read the standard input stream line-by-line and parse the key=value credential protocol format. The implementation of the ReadLineAsync method considers LF, CRLF, and CR as valid line endings. This is means that .NET considers a single CR as a valid newline character, whereas Git does not.

This mismatch of newline treatment between Git and GCM means that an attacker can craft a malicious remote URL such as:

https://\rhost=targethost@badhost

..which will be interpreted by Git as:

protocol=https host=badhost username=\rhost=targethost

This will instead be parsed by GCM as if the following has been passed by Git:

protocol=https host=badhost username= host=targethost

This results in the host field being resolved to the targethost value. GCM will then return a credential for targethost to Git, which will then send this credential to the badhost host.

Impact When a user clones or otherwise interacts[^3] with a malicious repository that requires authentication, the attacker can capture credentials for another Git remote. The attack is also heightened when cloning from repositories with submodules when using the --recursive clone option as the user is not able to inspect the submodule remote URLs beforehand.

Patches https://github.com/git-ecosystem/git-credential-manager/compare/749e287571c78a2b61f926ccce6a707050871ab8...99e2f7f60e7364fe807e7925f361a81f3c47bd1b

Workarounds Only interacting with trusted remote repositories, and do not clone with --recursive to allow inspection of any submodule URLs before cloning those submodules.

Fixed versions This issue is fixed as of version 2.6.1.

[^1]: The = character is also forbidden to form part of the key. [^2]: Carriage-return character (CR, \r), followed by a line-feed character. [^3]: Any remote operation such as fetch, ls-remote, etc.

Visual Studio Elevation of Privilege Vulnerability

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