CVE-2025-68119 Overview
CVE-2025-68119 is a local code execution vulnerability in the Go toolchain that affects systems with Mercurial (hg) or Git installed. The vulnerability arises from improper handling of malicious version strings when downloading and building modules from non-standard sources. Attackers can exploit this flaw to execute arbitrary code locally on systems with Mercurial, or achieve arbitrary file writes on systems with Git installed.
Critical Impact
Local code execution through maliciously crafted module version strings when using external version control systems with the Go toolchain.
Affected Products
- Go toolchain (systems with Mercurial installed)
- Go toolchain (systems with Git installed)
- Go modules from custom/non-standard domains
Discovery Timeline
- 2026-01-28 - CVE CVE-2025-68119 published to NVD
- 2026-01-29 - Last updated in NVD database
Technical Details for CVE-2025-68119
Vulnerability Analysis
This vulnerability stems from the Go toolchain's improper construction of external VCS (Version Control System) commands when processing module version strings. The issue manifests differently depending on which VCS is installed on the target system.
On systems with Mercurial (hg) installed, downloading modules from non-standard sources such as custom domains can lead to unexpected code execution. The vulnerability occurs because malicious version strings are not properly sanitized before being passed to external VCS commands, allowing command injection.
On systems with Git installed, the attack surface is more limited but still significant. Malicious version strings can be crafted to allow an attacker to write to arbitrary files on the filesystem. However, this variant requires explicitly providing the malicious version strings to the toolchain and does not affect standard usage patterns like @latest or bare module paths.
Root Cause
The root cause is insufficient input validation and improper sanitization of module version strings before they are incorporated into shell commands for external VCS operations. When the Go toolchain constructs commands for Mercurial or Git to fetch module dependencies, it fails to properly escape or validate version string parameters, creating an injection point for malicious input.
Attack Vector
The attack requires local access and leverages the Go module download mechanism. An attacker must either:
- Host a malicious module on a custom domain with a specially crafted version string (Mercurial attack path)
- Convince a developer to explicitly specify a malicious version string when using the Go toolchain (Git attack path)
The vulnerability is triggered during the module download and build process when external VCS commands are invoked with unsanitized version string parameters.
The attack exploits the way the Go toolchain passes version string parameters to external VCS binaries. When a malicious version string containing shell metacharacters or special VCS command arguments is provided, it can escape the intended context and execute arbitrary commands or manipulate file operations. The Mercurial variant is more dangerous as it can be triggered through normal module download operations from non-standard sources, while the Git variant requires explicit malicious input.
Detection Methods for CVE-2025-68119
Indicators of Compromise
- Unexpected process execution spawned from go commands involving hg or git subprocesses
- Unusual file writes in unexpected filesystem locations during module download operations
- Module version strings containing special characters, shell metacharacters, or command arguments
- Network connections to non-standard module hosting domains during build processes
Detection Strategies
- Monitor go get, go mod download, and go build commands for unusual subprocess behavior
- Implement file integrity monitoring on development systems to detect unauthorized file writes
- Audit module dependencies for non-standard hosting domains and unusual version string patterns
- Deploy endpoint detection rules for command injection patterns in VCS subprocess arguments
Monitoring Recommendations
- Enable verbose logging for Go toolchain operations in CI/CD pipelines
- Monitor for anomalous hg or git command executions with unusual arguments
- Implement network monitoring to detect connections to untrusted module hosting sources
- Review module download logs for version strings containing special characters or unexpected patterns
How to Mitigate CVE-2025-68119
Immediate Actions Required
- Update the Go toolchain to the latest patched version as referenced in the Go Developer Change Log
- Audit any custom module sources and version string specifications in existing projects
- Avoid downloading modules from non-standard or untrusted sources until patches are applied
- Remove or restrict access to Mercurial installations on development systems if not required
Patch Information
The Go development team has released a fix for this vulnerability. System administrators and developers should update their Go installations immediately. The patch addresses the improper handling of version strings when constructing external VCS commands.
For detailed patch information, refer to:
Workarounds
- Use only @latest or bare module paths instead of explicit version strings when possible
- Restrict module downloads to trusted, standard module proxies (e.g., proxy.golang.org)
- Configure GOPROXY environment variable to use only trusted proxies
- Temporarily uninstall Mercurial from development systems if not actively required for other purposes
# Configuration example
# Set GOPROXY to use only trusted module proxies
export GOPROXY="https://proxy.golang.org,direct"
# Alternatively, restrict to proxy only (no direct downloads)
export GOPROXY="https://proxy.golang.org"
export GONOSUMDB=""
export GOPRIVATE=""
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