CVE-2026-31817 — OliveTin

When the saveLogs feature is enabled, OliveTin persists execution log entries to disk. The filename used for these log files is constructed in part from the user-supplied UniqueTrackingId field in the StartAction API request. This value is not validated or sanitized before being used in a file path, allowing an attacker to use directory traversal sequences (e.g., ../../../) to write files to arbitrary locations on the filesystem.

Affected Code

Entry point — service/internal/api/api.go (line 130):

The UniqueTrackingId from the API request is passed directly to the executor without validation:

execReq := executor.ExecutionRequest{
    Binding:    pair,
    TrackingID: req.Msg.UniqueTrackingId, // user-controlled, no validation
    // ...
}

Tracking ID accepted as-is — service/internal/executor/executor.go (lines 508–512):

The tracking ID is only replaced with a UUID if it is empty or a duplicate. Any other string, including one containing path separators, is accepted:

_, isDuplicate := e.GetLog(req.TrackingID)

if isDuplicate || req.TrackingID == "" {
    req.TrackingID = uuid.NewString()
}

Filename construction — service/internal/executor/executor.go (line 1042):

The tracking ID is interpolated directly into the log filename:

filename := fmt.Sprintf("%v.%v.%v",
    req.logEntry.ActionTitle,
    req.logEntry.DatetimeStarted.Unix(),
    req.logEntry.ExecutionTrackingID,
)

File write — service/internal/executor/executor.go (lines 1068–1069 and 1082–1083):

The filename is joined to the configured log directory using path.Join, which calls path.Clean internally. path.Clean resolves .. path segments, causing the final file path to escape the intended directory:

// Results file (.yaml)
filepath := path.Join(dir, filename+".yaml")
err = os.WriteFile(filepath, data, 0600)

// Output file (.log)
filepath := path.Join(dir, filename+".log")
err := os.WriteFile(filepath, []byte(data), 0600)

Proof of Concept

An attacker sends the following StartAction request (Connect RPC or REST):

{
  "bindingId": "<any-executable-action-id>",
  "uniqueTrackingId": "../../../tmp/pwned"
}

Assuming the action title is Ping the Internet and the timestamp is 1741320000, the constructed filename becomes:

Ping the Internet.1741320000.../../../tmp/pwned

When path.Join processes this with a configured results directory like /var/olivetin/logs:

path.Join("/var/olivetin/logs", "Ping the Internet.1741320000.../../../tmp/pwned.yaml")

path.Clean resolves the traversal:

1. Path segments: ["var", "olivetin", "logs", "Ping the Internet.1741320000...", "..", "..", "..", "tmp", "pwned.yaml"]
2. The .. segments traverse upward past the log directory.
3. Final resolved path: /tmp/pwned.yaml

Two files are written:

• .yaml file — contains YAML-serialized InternalLogEntry (action title, icon, timestamps, exit code, output, tags, username, tracking ID)
• .log file — contains the raw command output (potentially attacker-influenced if the action echoes its arguments)

Impact

• Arbitrary file write to any path writable by the OliveTin process.
• OliveTin frequently runs as root inside Docker containers, so the writable scope is often the entire filesystem.
• An attacker could:
  • Overwrite OliveTin's own sessions.yaml to inject authenticated sessions.
  • Write to entity file directories to inject malicious entity data.
  • Write to system cron directories or other locations to achieve remote code execution.
  • Cause denial of service by overwriting critical system files.

Suggested Fix

Validate the UniqueTrackingId to ensure it only contains safe characters before use. A strict UUID format check is the simplest approach:

import "regexp"

var validTrackingID = regexp.MustCompile(`^[a-fA-F0-9\-]+$`)

// In ExecRequest, before accepting the user-supplied ID:
if req.TrackingID == "" || !validTrackingID.MatchString(req.TrackingID) {
    req.TrackingID = uuid.NewString()
}

Alternatively, sanitize the filename in stepSaveLog by stripping or rejecting path separators and .. sequences.