The discovery of CVE-2023-49569 exposed a strikingly dangerous gap in a widely used pure-Go Git library: maliciously crafted Git server replies can trigger a
path traversal flaw in go-git clients that, in the worst case, enables full
remote code execution (RCE) on hosts that consume untrusted repositories. This is not an academic edge case—the vulnerability is network-exploitable, affects production code paths used by many automation systems and cloud operators, and was given a
Critical severity rating by major vulnerability databases. (
nvd.nist.gov
Background / Overview
go-git is a pure-Go implementation of the Git protocol and filesystem helpers that many Go projects embed rather than shelling out to the
git binary. Because it operates in-process and implements file writes itself, mistakes in how it constructs and validates filesystem paths can directly impact the host running the application.
CVE-2023-49569 is a
path traversal implementation error that exists in go-git versions prior to
v5.11.0 (and in the older gopkg.in/src-d/go-git.v4 variants). When a client uses go-git’s default
chroot-style filesystem abstraction (called
ChrootOS, used by the library’s “Plain” functions such as
PlainClone), crafted server responses that include directory-traversal elements can cause the client to write files outside the intended repository worktree. Those writes can, in turn, be leveraged to place or modify files that lead to code execution—cron jobs, systemd units, startup scripts, or other autorun mechanisms depending on the host environment. The vulnerability is therefore
both a data-integrity failure and an avenue for remote compromise. (
nvd.nist.gov
The go-git maintainers addressed this issue in a fix that was released as
v5.11.0; vendors and distributions subsequently rolled the fix into downstream packages. Major trackers (NVD, OSV, Debian, Red Hat, Ubuntu and others) catalog the advisory and the fix guidance. (
osv.dev
How the vulnerability works — a technical deep dive
The attack surface: protocol responses vs. filesystem policy
At its core, this vulnerability is not about malformed Git objects or cryptographic weaknesses—it's about
trusting the server’s path information while creating files on disk. When go-git processes objects and constructs filesystem entries during clone/checkout operations, it relies on a filesystem abstraction layer (go-billy/osfs). One implementation of that layer,
ChrootOS, attempts to constrain file writes under a specific directory root, mirroring the typical "work-tree" behavior you expect when cloning. However, the implementation failed to fully neutralize special path segments delivered by a remote server (for example
../ sequences, absolute paths, or other crafted names), allowing a crafted response to escape the intended directory and land elsewhere on disk. (
osv.dev
Attack choreography (high level)
- An attacker controls or spoofs a Git server (or a mirror) that a victim’s go-git client will connect to.
- The malicious server advertises a repository that contains file entries whose paths include traversal sequences or unusual path constructs.
- The vulnerable client, using PlainClone/ChrootOS semantics, processes the server’s object list and writes files using the supplied paths without adequate sanitization.
- Files are written outside the intended repository root—into system directories or application-specific locations.
- The attacker relies on host behavior (a scheduled task, a service reload, or an operator running an installer script) to trigger execution of attacker-supplied content, or places files that give persistent footholds (e.g., added SSH keys, cron entries, init scripts). (security.snyk.io
Why the upstream git CLI is unaffected
The upstream Git CLI implements its own on-disk logic and performs different sanitization and sandboxing around writes. This is a go-git
implementation issue—applications that shell out to
git are not vulnerable for the same reasons. That distinction matters for mitigation and for how organizations assess risk across their toolchains. (
nvd.nist.gov
Scope and severity
- Affected library versions: go-git releases prior to v5.11.0 (including many v4 and early v5 releases used in downstream packages). Several vulnerability databases and package trackers list the affected ranges explicitly. (osv.dev
- Attack vector: Network. An attacker who can present a malicious Git server response (for example via a compromised mirror, malicious internal server, or interception) can exploit the issue without local privileges or user interaction. (nvd.nist.gov
- CVSS: NVD assigns CVSS v3.1 9.8 (Critical) for the path traversal leading to RCE scenario; some vendors’ local scoring may differ (for example, certain distro advisories show alternate scores for packaged components), but the consensus in public vulnerability catalogs is that this is a critical risk for affected deployments. (nvd.nist.gov
- Exploitability: Low complexity in the attack model—if the attacker controls the server side, the sanitized payload can be delivered during normal clone/fetch operations. Multiple vendor advisories therefore categorize the issue as high/critical. (security.snyk.io
Real-world impact and affected ecosystems
go-git is embedded in many kinds of systems:
- CI/CD systems and build controllers that perform git operations inside automation agents.
- Infrastructure and provisioning tools that pull configuration or modules from Git endpoints.
- Monitoring, dashboarding, and platform components that use in-process Git operations (some distributions ship binaries that embed go-git).
- Containerized operators, controllers, and platform tooling used in Kubernetes/OpenShift, where an injection of arbitrary filesystem writes can escalate to cluster-level persistence or container breakout when combined with other misconfigurations.
Several major vendors and downstream projects patched or re-released packages in response to the advisory—Red Hat and OpenShift, Debian and Ubuntu packages, Amazon Linux advisories and cloud images, and many Linux distributions and enterprise products updated component versions. That signals broad real-world exposure across both cloud and on-prem distributions. (
access.redhat.com
Notably, because the flaw only triggers when applications use
ChrootOS (default for certain plain clone/open flow functions), not every use of go-git is vulnerable. Applications that use the
BoundOS implementation, in-memory filesystems, or that explicitly sanitize paths before writing are not affected. Nevertheless, many codebases rely on the library defaults—so the practical blast radius remains large. (
security.snyk.io
Detection, mitigation, and remediation
If you maintain Go services or distributions that embed go-git, follow a layered approach: immediate mitigations, package upgrades, and long-term hardening.
Immediate actions (operational triage)
- Inventory: locate all services, binaries, and containers that embed go-git directly (github.com/go-git/go-git/v5) or indirectly (gopkg.in/src-d/go-git.v4). Build system dependency graphs and SBOMs to find where the library is used. This is the single highest-value step.
- Block untrusted servers: restrict which Git endpoints your infrastructure can contact. Enforce allowlists and require authenticated, signed endpoints for automated systems where possible. If an immediate upgrade is not feasible, this reduces exposure. (osv.dev
- Audit runtime behavior: search for processes that perform in-process clones or fetches using the library (PlainClone, PlainOpen, file transport protocols). Flag services that run as privileged user accounts or services with write access to sensitive host paths. (nvd.nist.gov
Patch and upgrade
- Upgrade go-git to v5.11.0 or later. The library maintainers released fixes that address the path normalization and write-safety checks; downstream package maintainers have incorporated the changes into distro releases. Verify your module dependency tree (go.mod) and vendor snapshots; update application builds and CI images accordingly. (osv.dev
- For projects using the older
gopkg.in/src-d/go-git.v4 imports, upgrade to a patched v4 release or migrate to the fixed v5 line as appropriate. The advisory applies across older v4 releases too, so ensure those packages are updated or replaced. (pkg.go.dev
- Rebuild and redeploy: rebuild any binary or container images that include go-git as a module dependency, test thoroughly, and rotate those components into production.
Code-level mitigations
- Avoid the library’s Plain helper functions in high-risk contexts. Prefer using BoundOS (or an in-memory filesystem) which restricts file creation to an explicit allowed tree. Where bound or chrooted filesystems are required, add additional path canonicalization and validation routines before performing file writes. (security.snyk.io
- Sanitize any path data received from remote repositories. Normalize paths, reject absolute paths and any path with
.. segments after canonicalization, and enforce application-level allowlists for write destinations.
- Run git operations under least-privileged service accounts and in hardened containers with minimal host filesystem mounts.
Detection & monitoring
- Add host-based detection rules: monitor for unexpected file creations outside expected work-tree directories, monitor for new cron entries, new systemd unit files, or sudden changes in privileged config paths.
- In CI, require signed commits and enforce repository source verification before running untrusted code. Treat any automated clone operation to an unsafe runtime as suspicious by default.
- Add dependency scanning to CI pipelines to detect vulnerable go-git versions. Modern SCA tools flag the exact advisory ranges. (security.snyk.io
Step-by-step upgrade checklist (recommended sequence)
- Run
go list -m all and go mod graph in repositories to enumerate direct and transitive go-git references.
- For each module that depends on go-git, update
go.mod to request github.com/go-git/go-git/v5 v5.11.0 (or later). Use go get github.com/go-git/go-git/[email]v5@v5.11.0[/email] then go mod tidy.
- Rebuild your artifacts and run existing test suites, focusing on clone/checkout and file-writing operations.
- Run dynamic tests in staging that simulate clone/fetch operations against controlled servers.
- Deploy to canary or staging environments and monitor file-system access logs for anomalies.
- Roll out the upgraded artifacts to production in standard canary/rollout fashion.
Why organizations still get blindsided: developer expectations vs. implementation risk
There are three common patterns that increase risk:
- Assumption that embedded Git libraries behave exactly like
git CLI. They do not; in-process libraries have different semantics and therefore different failure modes. Security reviews that only consider the CLI are blind to implementation-level issues such as this one. (nvd.nist.gov
- Use of default helpers (PlainClone) for convenience. Defaults designed for developer ergonomics sometimes favor fewer explicit parameters—those same defaults can implicitly enable ChrootOS semantics and thereby inherit the vulnerability. (security.snyk.io
- Lack of allowlisting for network destinations and insufficient isolation for automation agents. If a CI runner or controller can contact arbitrary Git endpoints and runs as a user who can write into sensitive host paths, a path traversal vulnerability becomes a low-cost, high-impact exploit vector. (access.redhat.com
Threat modeling: plausible exploitation scenarios
- Compromised mirror: An attacker compromises a mirror or public git hosting account that your CI occasionally fetches. When the CI clones the repo with a vulnerable go-git build, the attacker’s crafted paths escape the repo and plant a scheduled job in the host’s cron directory.
- Supply-chain poisoning: A malicious contributor publishes a package or module that downstream automation pulls; systems that auto-sync the repo and run build steps without strict vetting may execute attacker-supplied code or persist backdoors.
- Malicious internal host: An insider or attacker with access to company DNS/redirects could point internal tooling to a maliciously crafted server. If network restrictions are weak, automation quickly becomes the attack vector.
In each scenario the root cause is the same: an in-process Git parser accepting server-provided path values and writing files without robust canonicalization and policy checks. (
security.snyk.io
What the fix changed (developer-oriented summary)
The maintainers patched path handling and tightened the osfs implementations so that file writes are validated against an enforced base within the virtual filesystem. The fix also added additional checks on the library’s higher-level clone/open helpers, and updated tests to cover traversal attempts. Downstream package maintainers then rolled the fixed lib into published binaries and distro packages. If you rely on go-git, upgrading to the patched release is the definitive remediation step. (
osv.dev
Caveats, residual risks, and outstanding questions
- Not every go-git use is vulnerable: if your code uses BoundOS, an in-memory FS, or if you sanitize paths before handing them to the library, exposure is lower. Still, many projects rely on defaults, so operational checks are needed. (security.snyk.io
- Vendor-specific packaging may have different timelines for fixes. While upstream fixed the library, the cadence at which a vendor releases updated packages varies; confirm package versions in distro repositories and patch accordingly. Several OS vendors and platform vendors published advisories and CVE mappings—consult those advisories for precise package versions. (access.redhat.com
- Public proof-of-concept code: during our review of mainstream advisories and vendor briefings, there was no widely circulated, trusted public PoC that we could verify at the time of writing. That said, the basic exploit logic is straightforward if an attacker controls the server; organizations must assume it could be weaponized quickly. Where a PoC is published in untrusted repositories, treat it with caution—malicious PoCs are known to carry trojanized content. Always test fixes in isolated sandboxes. (github.com
Long-term lessons for developers and platform owners
- Treat in-process protocol implementations as first-class attack surfaces. Libraries that parse remote data and perform local writes should be subject to rigorous threat modeling just as you would treat network-facing services.
- Favor explicit filesystem policies. Defaults are helpful for developers, but security-sensitive systems should prefer explicit bindings (BoundOS or explicit FS wrappers) that make the intended write root unambiguous.
- Require network allowlisting for automation systems, and enforce E2E repository signing where feasible. Defense-in-depth—combining upgrades, network rules, and runtime containment—reduces the chance a single library bug leads to a full compromise.
- Integrate software bill-of-materials and dependency scanning into CI/CD pipelines. This vulnerability was reliably detected by SCA tools; early detection prevents vulnerable artifacts from entering production. (security.snyk.io
Practical checklist for sysadmins and SREs
- Inventory: identify all services that embed or vendor go-git.
- Prioritize: rank services by capability to write to host-sensitive locations (e.g., services running as root, with host mounts, or with system-level permissions).
- Patch: update to go-git v5.11.0 or the vendor-provided patched package. Rebuild containers and artifacts. (osv.dev
- Harden: add network allowlists for Git endpoints, run agents with least privilege, and containerize Git consumers with read-only root where possible.
- Monitor: add alerts for unexpected file writes to
/etc, /var, or other privileged locations.
- Test: in staging, run negative tests scanning clone outputs for
.. or absolute path entries prior to merge.
Conclusion
CVE-2023-49569 is an important reminder that convenience APIs and in-process protocol stacks can hide serious systemic risk. A seemingly small lapse in path normalization in a widely reused library translated into a feasible route to remote code execution for any system that accepted untrusted repositories using go-git’s default filesystem behavior. The corrective action is straightforward—
upgrade to go-git v5.11.0 (or patched vendor packages) and harden any automation that performs unattended clones—but the wider lesson is organizational: inventory, restrict, and treat embedded libraries as first-class components in both security reviews and operational risk models. (
osv.dev
If your teams perform automated cloning or in-process Git operations, treat this advisory as actionable: prioritize the upgrades and apply the layered mitigations described above. Stopping the next path-traversal-from-the-network exploit requires the same attention to details that prevented this one from becoming an even larger supply-chain incident.
Source: MSRC
Security Update Guide - Microsoft Security Response Center