git-lfs: Untrusted Search Path
CVE-2022-24826 is a high-severity untrusted search path vulnerability in git-lfs, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an unauthenticated attacker, but only if a user takes part, for example by opening a link or file. Affected git-lfs versions: 3.1.3. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 2.23% chance of exploitation within 30 days, higher than 83% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Git Large File Storage to 3.1.3 or a later version.
- Read the advisory on github.com for workarounds and exact fixed builds.
- Because the attack needs a user to take part, warn users about unexpected links and files related to this product until it is patched.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Git-lfs | git-lfs | 3.1.3 | Not stated |
| Git Large File Storage Project | Git Large File Storage | 2.12.1 up to, but not including, 3.1.3 | 3.1.3 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- RequiredA user must take an action such as opening a file or link.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 9.8 | Critical | CNA (github.com) |
| CVSS 3.1 | 7.8 | High | NVD |
| CVSS 2.0 | 4.4 | Medium | NVD |
Official description
On Windows, if Git LFS operates on a malicious repository with a `..exe` file as well as a file named `git.exe`, and `git.exe` is not found in `PATH`, the `..exe` program will be executed, permitting the attacker to execute arbitrary code. This does not affect Unix systems. Similarly, if the malicious repository contains files named `..exe` and `cygpath.exe`, and `cygpath.exe` is not found in `PATH`, the `..exe` program will be executed when certain Git LFS commands are run. More generally, if the current working directory contains any file with a base name of `.` and a file extension from `PATHEXT` (except `.bat` and `.cmd`), and also contains another file with the same base name as a program Git LFS intends to execute (such as `git`, `cygpath`, or `uname`) and any file extension from `PATHEXT` (including `.bat` and `.cmd`), then, on Windows, when Git LFS attempts to execute the intended program the `..exe`, `..com`, etc., file will be executed instead, but only if the intended program is not found in any directory listed in `PATH`. The vulnerability occurs because when Git LFS detects that the program it intends to run does not exist in any directory listed in `PATH` then Git LFS passes an empty string as the executable file path to the Go `os/exec` package, which contains a bug such that, on Windows, it prepends the name of the current working directory (i.e., `.`) to the empty string without adding a path separator, and as a result searches in that directory for a file with the base name `.` combined with any file extension from `PATHEXT`, executing the first one it finds. (The reason `..bat` and `..cmd` files are not executed in the same manner is that, although the Go `os/exec` package tries to execute them just as it does a `..exe` file, the Microsoft Win32 API `CreateProcess()` family of functions have an undocumented feature in that they apparently recognize when a caller is attempting to execute a batch script file and instead run the `cmd.exe` command interpreter, passing the full set of command line arguments as parameters. These are unchanged from the command line arguments set by Git LFS, and as such, the intended program's name is the first, resulting in a command line like `cmd.exe /c git`, which then fails.) Git LFS has resolved this vulnerability by always reporting an error when a program is not found in any directory listed in `PATH` rather than passing an empty string to the Go `os/exec` package in this case. The bug in the Go `os/exec` package has been reported to the Go project and is expected to be patched after this security advisory is published. The problem was introduced in version 2.12.1 and is patched in version 3.1.3. Users of affected versions should upgrade to version 3.1.3. There are currently no known workarounds at this time.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Untrusted Search Path
The product searches for critical resources using an externally-supplied search path that can point to resources that are not under the product's direct control.
How developers prevent this class of flaw
- Hard-code the search path to a set of known-safe values (such as system directories), or only allow them to be specified by the administrator in a configuration file. Do not allow these settings to be modified by an external party. Be careful to avoid related weaknesses such as CWE-426 and CWE-428.
- When invoking other programs, specify those programs using fully-qualified pathnames. While this is an effective approach, code that uses fully-qualified pathnames might not be portable to other systems that do not use the same pathnames. The portability can be improved by locating the full-qualified paths in a centralized, easily-modifiable location within the source code, and having the code refer to these paths.
- Remove or restrict all environment settings before invoking other programs. This includes the PATH environment variable, LD_LIBRARY_PATH, and other settings that identify the location of code libraries, and any application-specific search paths.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Advisories
- github.com/git-lfs/git-lfs/security/advisories/GHSA-6rw3-3whw-jvjjThird Party Advisory
Third-party and government advisories
- github.com/git-lfs/git-lfs/releasesThird Party Advisory
Other vulnerabilities in git-lfs
- 8.6 High severity
- 8.5 High severity
Recent Untrusted Search Path vulnerabilities
- 9.8 Critical severity
- 8.8 High severity
- 7.0 High severity
- 7.8 High severity
- 7.3 High severity
- 6.9 Medium severity
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