CVE-2021-21300 malicious repositories can execute remote code while cloning

What is CVE-2021-21300?

CVE-2021-21300 is a high-severity code injection vulnerability in Apple Xcode, published on 9 Mar 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

Official description

Git is an open-source distributed revision control system. In affected versions of Git a specially crafted repository that contains symbolic links as well as files using a clean/smudge filter such as Git LFS, may cause just-checked out script to be executed while cloning onto a case-insensitive file system such as NTFS, HFS+ or APFS (i.e. the default file systems on Windows and macOS). Note that clean/smudge filters have to be configured for that. Git for Windows configures Git LFS by default, and is therefore vulnerable. The problem has been patched in the versions published on Tuesday, March 9th, 2021. As a workaound, if symbolic link support is disabled in Git (e.g. via `git config --global core.symlinks false`), the described attack won't work. Likewise, if no clean/smudge filters such as Git LFS are configured globally (i.e. _before_ cloning), the attack is foiled. As always, it is best to avoid cloning repositories from untrusted sources. The earliest impacted version is 2.14.2. The fix versions are: 2.30.1, 2.29.3, 2.28.1, 2.27.1, 2.26.3, 2.25.5, 2.24.4, 2.23.4, 2.22.5, 2.21.4, 2.20.5, 2.19.6, 2.18.5, 2.17.62.17.6.

Weakness: CWE-59

Which versions are affected by CVE-2021-21300?

It affects 4 products.

Products include Apple Xcode, Debian Debian Linux, Fedoraproject Fedora, Git-Scm Git.

How do I fix CVE-2021-21300?

Upgrade to a fixed version.

Upgrade, and never evaluate templates, expressions or code built from user input. More about Code injection.

Is CVE-2021-21300 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-21300 exists.

Public exploit code: 1 Metasploit module and 14 proofs of concept on GitHub.

Other vulnerabilities in Apple Xcode

• CVE-2025-48384 Git Link Following Exploited High 8.1
• CVE-2014-9390 JGit Improper Input Validation vulnerability Critical 9.8
• CVE-2019-14379 Deserialization of untrusted data in FasterXML jackson-databind Critical 9.8
• CVE-2018-4164 An issue was discovered in certain Apple products. Critical 9.8
• CVE-2016-0746 Use after free in n/a Critical 9.8

All Apple Xcode vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as ALPINE-CVE-2021-21300, CLEANSTART-2026-PC25111, DEBIAN-CVE-2021-21300, GHSA-8prw-h3cq-mghm, MGASA-2021-0137, OESA-2021-1105 and 8 more.