CVE-2026-108259 — Code injection in @tinacms/cli from unescaped Git branch name

What happened

@tinacms/cli reads Git branch values from environment variables VERCEL_GIT_COMMIT_REF, GITHUB_BRANCH, or from HEAD and incorporates the raw value into an API URL that is interpolated into generated JavaScript string literals. A Git-valid branch name containing a quote can terminate the generated string and inject an expression that executes when the generated client module is imported during a preview build. (Sources: 4023, 32645, 32357)

Technical cause

The generated client source in @tinacms/cli inserts the branch value directly into JavaScript string literals in the codegen implementation (files named in the advisory). Because the branch value is not escaped before interpolation, a crafted branch name that includes a quote character can break out of the literal and inject executable code into the generated module. (Sources: 4023, 32645)

Why this matters

Injected code executes with the privileges of the build process during import of the generated client module. The advisory states the injected code can read environment credentials, modify deployment artifacts, or make network requests. This can expose secrets or alter build outputs. (Sources: 4023, 32645)

Who is affected

Projects that use the @tinacms/cli package and perform preview builds which import the generated client module are at risk. The issue arises when branch names are read from VERCEL_GIT_COMMIT_REF, GITHUB_BRANCH, or HEAD and then used to generate client source. (Sources: 4023, 32645, 32357)

Discovery and timeline

The advisory entries for this vulnerability were published on 2026-10-09 in multiple databases. See the referenced advisories for publication timestamps. (Sources: 4023, 32645, 32357)

Affected versions

According to the advisories, @tinacms/cli is affected from the initial published package (introduced at "0") and the issue is fixed in 3.0.0. One advisory lists the affected range as "<= 2.7.0". (Sources: 4023, 32645)

Fixes and mitigation

A fix is available: the advisories report the issue is fixed in 3.0.0. The sources do not list additional vendor workarounds in the advisory entries. (Sources: 4023, 32645)

Recommended action

Update @tinacms/cli to 3.0.0, as reported in the advisories. Review build-time permissions and environment variables used during preview builds until you can apply the update. (Sources: 4023, 32645)