Network UPS Tools EUVD-2026-88376

Exploitation requires the NUT repository's tarball-preparation GitHub Actions workflow (.github/workflows/01-make-dist-worker.yml) to run against an untrusted fork pull request while it holds a single-use write-permission GITHUB_TOKEN - the specific mis-structuring of privileged token context alongside PR-source-branch-controlled input. The attacker needs no repository credentials (fork PR only), but exploitation is limited to the brief interval while the GHA job runs and the token is valid, and depends on the vulnerable pre-patch workflow being present (before commits 658b24e and 1aa31d1). It affects only the NUT project's CI, not installed NUT UPS-monitoring deployments.

This is a GitHub Actions CI supply-chain flaw (CWE-829) in the Network UPS Tools repository, not a vulnerability in deployed NUT software. The CVSS 3.1 vector (AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:L, base 8.2) reflects that a malicious pull request from a fork could exfiltrate the write-scoped GITHUB_TOKEN because privileged token context was mixed with untrusted PR-controlled inputs. PR:N is technically correct (anyone can open a fork PR without repo access), but AC:H and UI:R capture real limiting factors: the poisoned workflow job must actually execute and the token is only abusable during the short lived job window. No EPSS score, no CISA KEV listing, and no public POC are provided - consistent with a scoped, repository-specific issue rather than mass-exploitable software. The high base score is driven by S:C plus C:H/I:H (token theft enabling repo/commit/comment manipulation), but real-world risk is bounded: the only 'deployment' of the vulnerable artifact is the single NUT repository's CI, the flaw is already patched (commits 658b24e and 1aa31d1), and the token's validity window is ephemeral. Treat as a genuine but narrow CI-hardening fix, not a broadly weaponizable NUT product vulnerability. Note the input Tags label this 'Information Disclosure', which fits token leakage but understates the integrity impact (repository content/status manipulation) that the description and I:H metric emphasize.

An attacker forks the NUT repository and opens a pull request whose source branch is crafted to hijack the tarball-preparation GitHub Actions workflow that runs with a write-permission GITHUB_TOKEN. When the job executes, the malicious PR code extracts the token value and, within the job's lifetime, uses it to push commits, forge check/status results, or post issue/PR comments per the token's granted permissions. No public exploit code is identified at time of analysis, though the pattern (pwn-request style CI token theft) is well known.