GHSA-fhgh-wq4q-r37x uniget CLI: Metadata signature verification only runs when UNIGET_IGNORE_METADATA_SIGNATURE is set
SummaryThe sigstore check on `metadata.json` is gated on the wrong side of the condition. `LoadMetadata` in `internal/config/update.go:81` verifies the bundle only when `UNIGET_IGNORE_METADATA_SIGNATURE` is non-empty, so in a normal run, where nobody sets that variable, the signature is never checked. Setting the variable that is named "ignore the signature" is what turns verification on.That matters because `metadata.json` populates `Tool.Check`, and `pkg/tool/tool.go:250` runs `Tool.Check` through `/bin/bash -c`. That is the same sink as CVE-2026-45152, and the signature check added in v0.27.1 to close it is the control that no longer runs.Where it is`internal/config/update.go:80-100`:`cmd/uniget/main.go:102-105` carries the same flipped condition in the decision about whether to re-download metadata:so a cached `metadata.json` with no `.sigstore.json` beside it is not refetched either, as long as the variable is unset.`LoadMetadata` is called from `cmd/uniget/main.go:115` in the persistent pre-run, which means every subcommand loads metadata this way. The sink is `pkg/tool/tool.go:248-251`:How it got this wayThe check was introduced correctly. In d12ef12c ("fix: Only accept signed metadata", released as v0.27.1) `VerifySigstoreBundle` was called unconditionally. 370d0155 then wrapped it in `if os.Getenv("UNIGET_IGNORE_METADATA_SIGNATURE") != "true"`, which is still the right polarity. b68a27d5 ("fix: Accept any non-empty value"), which is the commit tagged v0.27.4, rewrote that as `if len(os.Getenv("UNIGET_IGNORE_METADATA_SIGNATURE")) > 0`. The intent was clearly to accept any truthy value instead of the literal string "true", but the negation was dropped in the rewrite and the meaning flipped.Proof of conceptBuilt from a clean checkout of the v0.28.2 tag with `go build -o /tmp/unigetbin ./cmd/uniget`, then run in user mode against a poisoned cache with no `metadata.json.sigstore.json` present and `UNIGET_IGNORE_METADATA_SIGNATURE` explicitly removed from the environment.Observed output:and `/tmp/uniget-rce-proof.txt` contains the output of `id`. No signature error was raised, even though there is no bundle file at all.The control run is the part that pins down the polarity. Same command, same poisoned metadata, only now a `metadata.json.sigstore.json` exists (deliberately not a valid bundle) and the "ignore" variable is set:Observed output:So verification runs when the ignore variable is set, and does not run when it is unset.ImpactAnything that can substitute the metadata layer gets command execution as the user running uniget: a compromised or attacker-chosen registry or mirror for `uniget-org/tools`, a tampered tarball on the way into the cache, or a poisoned cache file. The sigstore bundle is the only thing standing between that metadata and `/bin/bash -c`, and right now it is not consulted. Locally this reproduces the CVE-2026-45152 scenario on a supposedly fixed version; the wider concern is that the supply chain check for the tool catalogue is effectively off for every user.Suggested fixInvert the condition so verification is the default and the environment variable opts out:The same inversion is needed at `cmd/uniget/main.go:104`, where the re-download decision should be "the bundle is missing and we are not ignoring signatures". It would also be worth failing closed when the `.sigstore.json` file is absent rather than treating a missing bundle as nothing to verify.DeduplicationCVE-2026-45152 (GHSA-qqq4-5773-pmw5) covers the `tool.Check` command injection itself and is marked patched in v0.27.1. This report is not that finding again: it is that the patch, which was the signature check, stopped running as of v0.27.4 because of the condition rewrite in b68a27d5. The other two published advisories, GHSA-m6jg-wr9m-cg2f and GHSA-qmcq-xw74-w667, are about hook file paths and the EDITOR variable and do not touch metadata loading.How I found it and a note on toolingI was reading the shipped fix for CVE-2026-45152 to see whether the guard covered all the paths that reach `RunVersionCheck`, and the gate condition read backwards on first pass, so I walked the history of that line back to the commit that introduced it. I used AI tooling while investigating, and I built the CLI at v0.28.2 and ran both the exploit and the control myself before writing this up.
CVSS v3.1 score: 7.8