Vulnerability · Published Mar 9, 2021 · Assigned by GitHub_M
CVE-2021-21300malicious repositories can execute remote code while cloning
High 8.0
In plain English
A high-severity security flaw in git from git. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 88.5% (higher than 99.8% of all known vulnerabilities). Ready-made attack tooling exists: Metasploit, public proof-of-concept code. Fixed versions are available - upgrade the affected package.
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine:v3.20 | git | 2.30.2-r0 | ALPINE-CVE-2021-21300 |
| Alpine:v3.21 | git | 2.30.2-r0 | ALPINE-CVE-2021-21300 |
| Alpine:v3.22 | git | 2.30.2-r0 | ALPINE-CVE-2021-21300 |
| Alpine:v3.23 | git | 2.30.2-r0 | ALPINE-CVE-2021-21300 |
| Alpine:v3.24 | git | 2.30.2-r0 | ALPINE-CVE-2021-21300 |
| Debian:12 | git | 1:2.30.2-1 | DEBIAN-CVE-2021-21300 |
| Debian:13 | git | 1:2.30.2-1 | DEBIAN-CVE-2021-21300 |
| Debian:14 | git | 1:2.30.2-1 | DEBIAN-CVE-2021-21300 |
Affected products (as reported)
Weakness: CWE-59 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:N
References
- https://github.com/git/git/security/advisories/GHSA-8prw-h3cq-mghm
- https://lore.kernel.org/git/xmqqim6019yd.fsf%40gitster.c.googlers.com/
- https://git-scm.com/docs/git-config#Documentation/git-config.txt-coresymlinks
- https://git-scm.com/docs/gitattributes#_filter
- https://github.com/git/git/commit/684dd4c2b414bcf648505e74498a608f28de4592
- [oss-security] 20210309 git: malicious repositories can execute remote code while cloning mailing-list
- FEDORA-2021-63fcbd126e vendor-advisory
- FEDORA-2021-ffd0b2108d vendor-advisory
- FEDORA-2021-03e61a6647 vendor-advisory
- https://support.apple.com/kb/HT212320
- 20210427 APPLE-SA-2021-04-26-10 Xcode 12.5 mailing-list
- GLSA-202104-01 vendor-advisory
- http://packetstormsecurity.com/files/163978/Git-LFS-Clone-Command-Execution.html
- [debian-lts-announce] 20221010 [SECURITY] [DLA 3145-1] git security update mailing-list