CVE-2026-26187

Two path traversal vulnerabilities in the local block adapter allow authenticated users to read and write files outside their designated storage boundaries.

Details

The local block adapter in pkg/block/local/adapter.go had two path traversal vulnerabilities:

1. Prefix Bypass Vulnerability

The verifyRelPath function used strings.HasPrefix() to verify that requested paths fall within the configured storage directory. This check was insufficient because it validated only the path prefix without requiring a path separator, allowing access to sibling directories with similar names.

Example: If the adapter is configured with base path /data/lakefs:

2. Namespace Escape via Identifier

The adapter verified that resolved paths stayed within the adapter's base path, but did not verify that object identifiers stayed within their designated storage namespace. This allowed attackers to use path traversal sequences in the object identifier to access files in other namespaces.

Example: With base path /data/lakefs and namespace local://repo1/userdata:

This vulnerability allows users with access to one namespace to read and write files in other namespaces within the same lakeFS deployment.

Workarounds

• Configure the storage path with a unique name unlikely to be a prefix of other directories
• Restrict filesystem permissions for the lakeFS process
• Ensure no sensitive data exists in sibling directories

Credit

Discovered via CodeQL static analysis.

Authenticated lakeFS users can:

• Read and write files in sibling directories that share the same path prefix as the storage directory (vulnerability 1)
• Access files across namespaces by using path traversal in object identifiers (vulnerability 2)

This could allow attackers to:

• Read sensitive data from other repositories/namespaces
• Write malicious files to other namespaces
• Read/write files in adjacent directories outside lakeFS storage
• Potentially escalate privileges if writable directories are used by other services

This vulnerability only affects deployments using the local block adapter. Deployments using S3, GCS, Azure, or other object storage backends are not affected.

Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files. Typical impact: unauthorized file read or write outside the intended directory.

CVE-2026-26187 has a CVSS score of 8.1 (High). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.77.0); upgrading removes the vulnerable code path.

Kodem intelligence

Fixed in version v1.77.0.

The fixes:

1. Append a path separator to prefix checks, ensuring paths must be within the storage directory
2. Add two-level path validation: verify both that namespace paths stay within the adapter's base path AND that resolved paths stay within their designated namespace

1. What is CVE-2026-26187? CVE-2026-26187 is a high-severity path traversal vulnerability in github.com/treeverse/lakefs (go), affecting versions <= 1.76.0. It is fixed in 1.77.0. Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files.
2. How severe is CVE-2026-26187? CVE-2026-26187 has a CVSS score of 8.1 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of github.com/treeverse/lakefs are affected by CVE-2026-26187? github.com/treeverse/lakefs (go) versions <= 1.76.0 is affected.
4. Is there a fix for CVE-2026-26187? Yes. CVE-2026-26187 is fixed in 1.77.0. Upgrade to this version or later.
5. Is CVE-2026-26187 exploitable, and should I be worried? Whether CVE-2026-26187 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-26187 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-26187? Upgrade github.com/treeverse/lakefs to 1.77.0 or later.