CVE-2015-0839

What it actually does

The hp-plugin utility accepts GPG signatures verified only by short key IDs fetched from a keyserver, allowing an attacker controlling the network path to substitute a colliding key and deliver a malicious print plugin that executes with the privileges of the invoking user.

Why it matters to the business

Compromise of Linux workstations or servers that use HPLIP for printing can result in arbitrary code execution, enabling attackers to persist, exfiltrate data, or move laterally without user interaction.

How an attack unfolds

An attacker on the same network or controlling a transit point intercepts the hp-plugin download of a print plugin and its GPG signature, supplies a malicious plugin paired with a short-key-ID collision that verifies successfully, and the utility installs and executes the attacker-controlled code.

How to fix it

Upgrade HPLIP to a version that performs GPG verification using full key fingerprints instead of short key IDs; if an upgrade is unavailable, disable the hp-plugin utility or restrict its use to offline, manually verified plugins.

How to confirm the fix worked

Confirm that hp-plugin source code or configuration now requires full 40-character GPG fingerprints for signature validation and that plugin downloads are performed only over authenticated TLS connections with certificate pinning where possible.

Typical attack path

1. Establish man-in-the-middle position on the path between the victim system and the HPLIP keyserver or plugin repository
2. Trigger or wait for hp-plugin to request a print plugin download
3. Substitute the legitimate plugin and signature with attacker-controlled versions that satisfy the short GPG key ID check
4. Allow hp-plugin to complete verification and installation, resulting in execution of the malicious payload

How to detect it

Review system logs for hp-plugin invocations, GPG keyserver queries returning short key IDs, and unexpected files written to HPLIP plugin directories; correlate with network captures showing plugin downloads from unexpected sources.

What your security team should do

• Immediately inventory all systems running HPLIP and prioritize upgrade of the package to the latest maintained release
• Block or monitor outbound connections from hp-plugin to external keyservers until verification logic is confirmed fixed
• Add HPLIP plugin installation events to endpoint monitoring and alert on unexpected binaries or libraries dropped into print-related directories