7.5

CVSS Score

3.1

-

CVSS Score

Basic Information

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CVE-2026-40938

CVE-2026-40938: Tekton Pipelines: Git Resolver Unsanitized Revision Parameter Enables git Argument Injection Leading to RCE

Tekton Pipelines project provides k8s-style resources for declaring CI/CD-style pipelines. From 1.0.0 to before 1.11.0, the git resolver's revision parameter is passed directly as a positional argument to git fetch without any validation that it does not begin with a - character. Because git parses flags from mixed positional arguments, an attacker can inject arbitrary git fetch flags such as --upload-pack=<binary>. Combined with the validateRepoURL function explicitly permitting URLs that begin with / (local filesystem paths), a tenant who can submit ResolutionRequest objects can chain these two behaviors to execute an arbitrary binary on the resolver pod. The tekton-pipelines-resolvers ServiceAccount holds cluster-wide get/list/watch on all Secrets, so code execution on the resolver pod enables full cluster-wide secret exfiltration. This vulnerability is fixed in 1.11.1.

(GitHub Advisory)

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CVE-2026-40938

CVE-2026-40938:

7.5

CVSS Score

3.1

-

CVSS Score

Basic Information

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Technical Details

Package Name	Ecosystem	Vulnerable Versions	First Patched Version
github.com/tektoncd/pipeline	go	>= 1.0.0, <= 1.11.0	1.11.1

Technical Details

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Root Cause Analysis

The vulnerability is a git argument injection flaw within the Tekton Pipeline's git resolver. The root cause lies in the checkout function in pkg/resolution/resolver/git/repository.go, which passed a user-controlled revision parameter to a git fetch command without proper sanitization. Specifically, it failed to prevent the revision from being interpreted as a command-line flag.

Two other functions contributed to this vulnerability:

PopulateDefaultParams in pkg/resolution/resolver/git/resolver.go did not validate if the revision parameter started with a -, allowing malicious arguments to be passed through.
validateRepoURL in the same file allowed local filesystem paths as valid git repository URLs. This was critical for the exploit, as the injected --upload-pack command is executed on the local pod when the git remote is a local path.

An attacker could exploit this by crafting a ResolutionRequest with a revision parameter like --upload-pack=/path/to/binary and a url parameter pointing to a local path on the resolver pod. This would cause the git fetch command to execute the specified binary, leading to remote code execution with the permissions of the resolver pod. The patch addresses this by validating the revision parameter, disallowing local repository URLs, and adding a -- separator to git commands to strictly separate flags from positional arguments.

Vulnerable functions

github.com/tektoncd/pipeline/pkg/resolution/resolver/git.(*repository).checkout

pkg/resolution/resolver/git/repository.go

The `checkout` function passed the user-controlled `revision` string directly to an external `git fetch` command. An attacker could provide a `revision` value starting with `-`, such as `--upload-pack=/path/to/binary`, which `git` would interpret as a command-line flag rather than a revision identifier. This allowed for argument injection, leading to arbitrary code execution.

github.com/tektoncd/pipeline/pkg/resolution/resolver/git.PopulateDefaultParams

pkg/resolution/resolver/git/resolver.go

This function was responsible for processing and validating input parameters but lacked a check to prevent the `revision` parameter from starting with a `-`. This omission allowed a malicious, flag-like string to be passed to the `checkout` function, enabling the argument injection vulnerability.

github.com/tektoncd/pipeline/pkg/resolution/resolver/git.validateRepoURL

pkg/resolution/resolver/git/resolver.go

This function validated the repository URL and explicitly permitted local filesystem paths (i.e., paths starting with `/`). This was a key contributing factor to the vulnerability, as the `--upload-pack` argument is executed on the local machine when `git fetch` is used with a local repository path, enabling the remote code execution.

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WAF Rule

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Reasoning

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