CVE-2025-48056: Hubble CLI Information Disclosure Flaw

CVE-2025-48056 Overview

CVE-2025-48056 affects Hubble, a distributed networking and security observability platform for cloud native workloads built on Cilium. Prior to version 1.17.2, a network attacker can inject malicious control characters into Hubble CLI terminal output. The flaw stems from insufficient neutralization of special elements in output rendered to the terminal [CWE-74]. Exploitation requires the victim to be monitoring Kafka traffic using Layer 7 (L7) Protocol Visibility at the time of the attack. Successful injection allows attackers to conceal log entries, rewrite output, or render the terminal temporarily unusable.

Critical Impact
A remote attacker can manipulate Hubble CLI terminal output through crafted Kafka traffic, undermining the integrity of security observability data used by defenders.

Affected Products

Hubble CLI versions prior to 1.17.2
Cilium deployments using Hubble with Kafka L7 Protocol Visibility enabled
Cloud native environments relying on Hubble flow monitoring for Kafka

Discovery Timeline

2025-05-20 - CVE-2025-48056 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-48056

Vulnerability Analysis

Hubble provides real-time visibility into network flows across Kubernetes clusters. When L7 Protocol Visibility is enabled for Kafka, Hubble parses Kafka protocol messages and surfaces fields such as topic names and client identifiers in CLI output. The vulnerability arises because these attacker-influenced fields are written to the terminal without sanitizing ANSI escape sequences or other control characters. An attacker who can send Kafka traffic observed by a Hubble-monitored workload can embed control sequences inside protocol fields. When a defender runs hubble observe and views the flow, the terminal interprets those sequences instead of displaying them literally.

Root Cause

The root cause is improper neutralization of special elements in output ([CWE-74]) in the Hubble CLI rendering path for Kafka L7 flows. Untrusted protocol data reaches the terminal without escaping, allowing ANSI escape codes and other control characters to be interpreted by the user's terminal emulator.

Attack Vector

The attack vector is network-based and requires no authentication or user interaction beyond an operator actively monitoring Kafka flows. An attacker sends crafted Kafka messages containing control characters within fields such as topic names or client IDs. When those flows are observed via the Hubble CLI, the malicious sequences execute terminal rendering behaviors — for example, moving the cursor to overwrite prior lines, clearing the screen, or altering displayed colors — enabling concealment of malicious activity or forgery of legitimate-looking entries.

No verified proof-of-concept code has been published. See the GitHub Security Advisory GHSA-274q-79q9-52j7 and the upstream fix in Cilium PR #37401 for technical details.

Detection Methods for CVE-2025-48056

Indicators of Compromise

Hubble flow records containing non-printable or ANSI escape byte sequences (e.g., 0x1B[ sequences) inside Kafka topic names, client IDs, or other L7 fields.
Unexpected visual anomalies in hubble observe output such as missing lines, overwritten text, or altered colors.
Kafka traffic from unusual sources targeting monitored workloads with malformed or unusually structured protocol fields.

Detection Strategies

Redirect Hubble flows to a log file and scan for control-character byte patterns using tools such as grep -P "\\x1b\[" or cat -v.
Inspect Kafka broker logs for topic names or client identifiers containing non-ASCII or control bytes.
Compare Hubble CLI output against the raw JSON export (hubble observe -o json) to detect discrepancies caused by terminal rendering.

Monitoring Recommendations

Ingest Hubble flow logs into a centralized logging pipeline where control characters are rendered inertly rather than interpreted.
Alert on Kafka L7 flow fields containing byte values outside expected printable ranges.
Track Hubble CLI version inventory across clusters to identify hosts still running versions prior to 1.17.2.

How to Mitigate CVE-2025-48056

Immediate Actions Required

Upgrade Hubble CLI to version 1.17.2 or later on all workstations used to monitor Cilium clusters.
Audit which clusters have Kafka L7 Protocol Visibility enabled and prioritize patching those environments.
Instruct operators to avoid running hubble observe against untrusted Kafka traffic on unpatched CLI versions.

Patch Information

The issue is fixed in Hubble CLI v1.17.2. The corresponding upstream change is available in Cilium Pull Request #37401, which sanitizes control characters in Kafka L7 flow output before rendering.

Workarounds

Direct Hubble flows to a log file with hubble observe > flows.log and inspect the output within a text editor that does not interpret ANSI escape sequences.
Use JSON output mode (hubble observe -o json) and process flows programmatically rather than viewing raw terminal output.
Disable Kafka L7 Protocol Visibility in Cilium Network Policies until the CLI can be upgraded.

bash

# Redirect Hubble flows to a file for safe inspection on unpatched CLI versions
hubble observe --protocol kafka > kafka-flows.log

# Or export as JSON to avoid terminal interpretation of control characters
hubble observe --protocol kafka -o json > kafka-flows.json