Google Cloud Build CVE-2026-19410

Exploitation requires a Google Cloud Build GitHub trigger that is configured with Trigger Comment Control (the approval-comment gate for external-contributor pull requests) prior to the 2026-06-24 fix; the attacker must be able to submit a pull request or webhook event to that repository (PR:L - some GitHub-side standing, not fully anonymous) and apply the 'webhook suppression' technique to bypass the approval requirement. Limiting factors: only repositories that enable Comment Control are affected, and UI:P indicates the flow still involves a maintainer/passive user element rather than pure unauthenticated automation; repositories without GitHub integration or without Comment Control gating are not in scope. This is not a default-configuration unauthenticated flaw - it targets the specific comment-approval feature.

This is a genuinely high-severity issue: the vendor CVSS 4.0 score is 9.4 with a network vector (AV:N), low attack complexity (AC:L), only low privileges required (PR:L), and high impact to confidentiality, integrity and availability of both the vulnerable and subsequent systems (VC/VI/VA:H, SC/SI/SA:H), reflecting that code execution in a CI build environment typically yields access to the build service account, source, and secrets. The counterweight is UI:P (passive user interaction) - exploitation depends on a repository actually being configured with GitHub Comment Control and on a maintainer's involvement, so it is not a fully unconditional drive-by. There is no CISA KEV listing and no public POC, so this is a serious authorization-bypass with real supply-chain consequences rather than a confirmed mass-exploited event; any organization running GitHub-triggered Cloud Build with external-contributor PR gating should treat it as urgent because a successful bypass reaches production build credentials. Note the internal inconsistency worth flagging to defenders: the description and title say 'Incorrect Authorization' while the CWE is CWE-367 (TOCTOU) - the label differs but both point to the approval gate being unreliable.

An outside contributor opens a pull request against a repository whose Cloud Build trigger is gated by GitHub Comment Control, then uses the webhook-suppression technique to defeat the maintainer-approval requirement, causing Cloud Build to run the PR's unreviewed code. The build executes with the trigger's service-account privileges, giving the attacker code execution in the CI environment and potential access to build secrets and artifacts. No public exploit code is known, and the attack requires a repository actually configured with Comment Control.