# Crossplane's TOCTOU between cosign verification and image fetch in xpkg.CachedClient allows tag-based package install to bypass signature check

Advisory record · `GHSA-mf7q-r4rv-jv94`

- **Identifiers:** `GHSA-mf7q-r4rv-jv94` · `CVE-2026-105163` · `GO-2026-6302`
- **State:** Confirmed
- **Severity:** CVSS 6.9 Medium
- **Critical:** No
- **Weakness (CWE):** [CWE-345](https://cwe.mitre.org/data/definitions/345.html) · [CWE-362](https://cwe.mitre.org/data/definitions/362.html) · [CWE-367](https://cwe.mitre.org/data/definitions/367.html)
- **Tags:** [Race condition](https://agentprime.io/advisories/tag/race-condition.md) · [CWE-345](https://agentprime.io/advisories/tag/cwe-345.md)
- **Published:** 27 Aug 2026
- **Updated:** 5 Oct 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 27 Aug 2026, 17:25 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `github.com/crossplane/crossplane-runtime/v2` (Go): affected `>=2.4.0-rc.0, <2.4.0-rc.1 || >=2.3.0, <2.3.3`; fixed in `2.4.0-rc.1`, `2.3.3`

## Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

> Crossplane runtime (Go module github.com/crossplane/crossplane-runtime/v2) versions 2.3.0 up to 2.3.3 and 2.4.0-rc.0 up to 2.4.0-rc.1 are affected. When packages are installed by tag and signature verification is enabled, a malicious registry can serve a signed image for verification and an unsigned image for installation. Upgrade to 2.3.3 or 2.4.0-rc.1. Installing packages by image digest instead of tag avoids the issue.

Written 1 Nov 2026.

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 6.9 Medium, CVSS 4.0: `CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X`, from CNA (VulDB)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0032, the 25th percentile, on 9 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 14:12 UTC: First seen by agentprime
- 31 Oct 2026, 14:12 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-mf7q-r4rv-jv94)

## Sources

- [GitHub Advisory Database: GHSA-mf7q-r4rv-jv94](https://github.com/advisories/GHSA-mf7q-r4rv-jv94)
- [OSV: GHSA-mf7q-r4rv-jv94](https://osv.dev/vulnerability/GHSA-mf7q-r4rv-jv94)
- <https://github.com/crossplane/crossplane-runtime/security/advisories/GHSA-mf7q-r4rv-jv94>
- <https://github.com/crossplane/crossplane-runtime>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-mf7q-r4rv-jv94>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-mf7q-r4rv-jv94/>. Everything for agents: <https://agentprime.io/llms.txt>.