CVE-2026-73294: Semaphore U: OS Command Injection

Should you act?

Critical, preconditions apply

Severe if exploited, but exploitation needs conditions that may not apply to you. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• Not in CISA KEV, but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
• EPSS 0.7%, percentile 50: FIRST’s model estimates a 0.7% chance of exploitation activity in the next 30 days, higher than 50% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
• Needs an account (low (any account)). Exposure depends on who can log in.
• Only applies if your dependency tree includes github.com/semaphoreui/semaphore (Go) < 0.0.0-20260704181911-7e8a9434bd81, fixed in 0.0.0-20260704181911-7e8a9434bd81. Check your lockfile, including transitive dependencies.

What it is

Semaphore UI is a web interface for managing DevOps tools. Prior to 2.18.17 and 2.19.5-beta2, repository giturl handling passes an attacker-controlled --upload-pack option to CmdGitClient.GetLastRemoteCommitHash through POST /api/project/{id}/repositories and scheduled commit-hash polling, allowing a project Manager or Owner to execute arbitrary OS commands in the Semaphore server process. This issue is fixed in versions 2.18.17 and 2.19.5-beta2.

From the GitHub advisory

Summary An OS command injection in repository giturl handling lets any user holding the Manager or Owner role on any project (the normal project-collaborator roles) achieve remote code execution on the Semaphore server host. Using git's --upload-pack= option, an attacker runs arbitrary commands. The command executes inside the main Semaphore server process (via the schedule commit-hash poller), so it runs even when jobs are configured for remote runners — bypassing runner isolation and exposing the master encryption key and every project's secrets. Reproducible on a default install (gitclient: cmdgit); no non-default configuration is required.

Details The repository giturl is attacker-controlled (HTTP body) and reaches exec.Command("git", ...) unvalidated. Two missing controls cause this:

1. giturl is never validated against option injection. Repository.Validate() (db/Repository.go, ~lines 138–156) validates the branch via ValidateGitBranch (db/gitbranch.go, which rejects a leading -), but performs no equivalent check on GitURL (only "non-empty"). ValidateRepository (db/Store.go, ~802–806) only checks the SSH key. CreateRepository (db/sql/repository.go, ~76–95) stores it verbatim. Because --upload-pack=... has no scheme:// and no leading /, GetType() (db/Repository.go, ~113–136) classifies it as RepositorySSH and GetGitURL(false) (~72–111) returns it raw/unchanged.

2. The git command is built with no -- separator. CmdGitClient.GetLastRemoteCommitHash (dblib/CmdGitClient.go, ~169–185) calls: c.output(r, GitRepositoryTmpPath, "ls-remote", r.Repository.GetGitURL(false), // attacker-controlled r.Repository.GitBranch) // "master" output (~79–93) → makeCmd (~21–60): exec.Command("git") (line ~27), cmd.Args = append(cmd.Args, args...) (line ~55). The resulting argv has no --: ["git", "ls-remote", "--upload-pack= ;true", "master"] git parses --upload-pack=... as an option; master becomes the (local-transport) repository operand; git then executes the upload-pack value through a shell (sh -c " 'master'"), running . This is intended git behavior — the fault is Semaphore passing untrusted data as argv. (The command runs even though git subsequently prints fatal: Could not read from remote repository and exits 128, and even though master is not a real path.)

Trigger — it fires in the server…

Weakness type: CWE-78, CWE-88.

Product: github.com/semaphoreui/semaphore (Go) · Assigned by: GitHub_M · Published: 2026-08-12

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: low (any account)
• User interaction: none
• Scope: changed (can affect other components)

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation poc, automatable no, technical impact total.
• FIRST EPSS (model of 2026-10-21): 0.65% probability of exploitation activity in the next 30 days; percentile 50.

Timeline

• 2026-08-12 — CVE record last updated
• 2026-08-12 — CVE record published by GitHub_M
• 2026-09-08 — GitHub-reviewed advisory GHSA-xp7j-h7jc-4w8p published (critical)

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-xp7j-h7jc-4w8p github.com
2. CVE.org record CVE-2026-73294 cve.org
3. NVD entry CVE-2026-73294 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com
3. github.com github.com
4. github.com github.com
5. github.com github.com

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