CVE-2026-56748 Overview
CVE-2026-56748 is a symbolic link validation vulnerability [CWE-61] in the Pack Git import feature of Cribl Stream. Versions prior to 4.18.2 fail to properly validate symbolic links inside imported Git repositories. A remote authenticated attacker holding Pack import and pipeline preview permissions can execute arbitrary code as the Cribl server process. The attack requires a crafted Git repository containing a symbolic link inside the pack's functions directory. Successful exploitation results in code execution within the context of the Cribl server, granting the attacker access to data, credentials, and downstream systems reachable by the process.
Critical Impact
Authenticated remote code execution as the Cribl server process through a malicious symlink in an imported Git pack.
Affected Products
- Cribl Stream versions prior to 4.18.2
- Deployments exposing the Pack Git import feature to users
- Environments where the Cribl server process holds sensitive file or network access
Discovery Timeline
- 2026-07-27 - CVE-2026-56748 published to NVD
- 2026-07-30 - Last updated in NVD database
Technical Details for CVE-2026-56748
Vulnerability Analysis
Cribl Stream supports importing Packs from Git repositories to distribute reusable pipeline logic, functions, and configuration. During import, the Pack Git feature processes files under the pack directory structure, including the functions subdirectory that holds executable JavaScript components used by pipelines. The import routine does not sufficiently validate whether entries in the repository are symbolic links pointing outside the pack root. This allows an attacker-controlled Git repository to place symlinks that resolve to arbitrary paths on the Cribl server file system. When the pipeline preview function later loads or evaluates the symlinked file, the server executes attacker-controlled content in the process context. The Pack import and pipeline preview permissions together form the minimum privilege set required.
Root Cause
The root cause is improper validation of symbolic links [CWE-61] during Git-based Pack import. The importer trusts the layout of the repository and follows symbolic link entries without confirming that their targets remain within the intended pack directory. This is a classic symlink-following flaw compounded by the fact that the follow-up pipeline preview step loads and runs code from the resolved path.
Attack Vector
An authenticated user with Pack import and pipeline preview privileges hosts a Git repository containing a pack whose functions directory includes a symbolic link. The link targets a file the attacker wants executed or a location where they can drop code. The user triggers a Pack import in Cribl Stream against this repository, then invokes a pipeline preview referencing the crafted function. The Cribl server resolves the symlink and executes the referenced content as the Cribl service account. Because the attack occurs over the network with low complexity and requires only low-privilege authentication, exposure is broad for tenants that delegate pack management to non-administrative roles.
No public proof-of-concept code is available. Refer to the Cribl Release Notes v4.18.2 for vendor-provided technical context.
Detection Methods for CVE-2026-56748
Indicators of Compromise
- Pack import events referencing external or unexpected Git repository URLs
- Presence of symbolic link entries within any imported pack's functions directory
- Unexpected child processes spawned by the Cribl server process following a pipeline preview action
- Outbound network connections from the Cribl host initiated shortly after a pack import or preview
Detection Strategies
- Audit Cribl Stream logs for Pack import and pipeline preview actions correlated by user and time window
- Scan imported pack directories on disk for symlinks using find <packs_dir> -type l and alert on any hits
- Monitor process ancestry on Cribl hosts and flag non-standard executables launched under the Cribl service account
- Review Git repository sources against an allowlist of approved internal remotes
Monitoring Recommendations
- Forward Cribl application and audit logs to a centralized analytics platform for correlation with endpoint telemetry
- Alert on file system writes to functions directories originating from Git import workflows
- Track privilege assignments for the Pack import and pipeline preview roles and review changes regularly
- Baseline outbound network activity from Cribl servers and alert on new destinations
How to Mitigate CVE-2026-56748
Immediate Actions Required
- Upgrade Cribl Stream to version 4.18.2 or later without delay
- Restrict Pack import and pipeline preview permissions to a minimal set of trusted administrators
- Review recent pack imports for symbolic links inside functions directories and remove suspicious packs
- Rotate credentials and secrets accessible to the Cribl server process if compromise is suspected
Patch Information
Cribl addressed CVE-2026-56748 in Cribl Stream 4.18.2. Details are published in the Cribl Release Notes v4.18.2 and the Cribl Security Notifications portal. Apply the vendor upgrade path suitable for your deployment topology, including distributed worker groups and leader nodes.
Workarounds
- Disable Git-based Pack import until the upgrade is applied
- Limit Pack import sources to internally hosted, access-controlled Git repositories
- Revoke Pack import and pipeline preview permissions from non-administrative roles
- Run the Cribl server process under a dedicated low-privilege service account with restricted file system and network access
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
