CVE-2024-24806: Libuv Hostname Truncation SSRF Vulnerability

CVE-2024-24806 Overview

CVE-2024-24806 is a Server-Side Request Forgery (SSRF) vulnerability in libuv, a multi-platform support library with a focus on asynchronous I/O. The vulnerability exists in the uv_getaddrinfo function where hostnames are truncated to 256 characters before being passed to the system's getaddrinfo function. This truncation occurs without proper null termination, enabling attackers to craft malicious hostnames that resolve to unintended IP addresses, potentially bypassing security controls and accessing internal services.

Critical Impact

Attackers can exploit this hostname truncation flaw to craft payloads that resolve to internal IP addresses like 127.0.0.1, enabling SSRF attacks that bypass developer-implemented security checks and potentially expose internal APIs and services.

Affected Products

• libuv versions prior to 1.48.0
• Applications using libuv for DNS resolution (including Node.js and related projects)
• Services that process user-controlled hostnames through libuv's uv_getaddrinfo function

Discovery Timeline

• 2024-02-07 - CVE-2024-24806 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2024-24806

Vulnerability Analysis

The vulnerability stems from improper input validation in libuv's hostname resolution mechanism. The uv_getaddrinfo function in both Unix (src/unix/getaddrinfo.c) and Windows (src/win/getaddrinfo.c) implementations uses a fixed-size buffer called hostname_ascii with a length of 256 bytes. When a hostname exceeding 256 characters is processed, the buffer is filled without appending a terminating null byte.

This truncation behavior creates a dangerous condition where specially crafted hostnames can be manipulated to resolve to arbitrary IP addresses. For example, an attacker could create a hostname like 0x00007f000001 (which represents 127.0.0.1 in hexadecimal) that gets validated by application-level checks as an external address but resolves to localhost after truncation.

The flaw is particularly dangerous in scenarios involving user-controlled subdomains, such as platforms that allow users to have username.example.com pages. Internal services that crawl or cache these pages become vulnerable to SSRF attacks when a malicious user selects a carefully crafted long username.

Root Cause

The root cause is a boundary condition error in the hostname handling logic within the uv__idna_toascii function and the uv_getaddrinfo wrapper. The code fails to properly validate hostname length before truncation and does not ensure null termination after copying data into the fixed-size hostname_ascii buffer. This creates a classic input validation vulnerability where the truncated hostname can be interpreted differently than the original input.

Attack Vector

The attack exploits the network-accessible DNS resolution functionality. An attacker with no special privileges can submit a maliciously crafted hostname to any application using vulnerable versions of libuv for address resolution. The attack requires no user interaction and can be executed remotely.

The attack scenario typically involves:

1. An attacker identifies a service that processes user-controlled hostnames through libuv
2. The attacker crafts a hostname exceeding 256 characters that, when truncated, resolves to an internal IP address
3. Application-level hostname validation passes because it sees the full, seemingly external hostname
4. libuv truncates the hostname and resolves it to an internal address
5. The service connects to the internal resource, enabling the SSRF attack

For detailed technical analysis, refer to the GitHub Security Advisory and discussions on the OpenWall Security Mailing List.

Detection Methods for CVE-2024-24806

Indicators of Compromise

• Unusually long hostnames (exceeding 256 characters) in DNS resolution logs
• Network connections to internal IP ranges (e.g., 127.0.0.0/8, 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) originating from services that should only connect externally
• Application logs showing hostname resolution for addresses containing hexadecimal representations of IP addresses

Detection Strategies

• Implement monitoring for DNS queries with hostnames exceeding 256 characters
• Configure network segmentation alerts for outbound services attempting to reach internal IP ranges
• Deploy application-level logging to capture and analyze hostname resolution requests before and after processing
• Use SentinelOne's behavioral AI to detect anomalous network connection patterns indicative of SSRF exploitation

Monitoring Recommendations

• Enable verbose logging for libuv-based applications to capture hostname resolution activities
• Configure SIEM rules to alert on connections from web-facing services to internal metadata endpoints (e.g., cloud provider metadata services at 169.254.169.254)
• Monitor for scanning activity targeting internal services from externally-facing application servers

How to Mitigate CVE-2024-24806

Immediate Actions Required

• Upgrade libuv to version 1.48.0 or later immediately
• Audit all applications using libuv as a dependency and update their libuv versions
• Implement network-level controls to restrict internal service access from potentially vulnerable services
• Review and enhance hostname validation at the application layer to reject hostnames exceeding 256 characters

Patch Information

The libuv maintainers have addressed this vulnerability in release version 1.48.0. Multiple commits were published to fix the issue across different branches:

• Commit 0f2d7e7
• Commit 3530bcc
• Commit c858a14
• Commit e0327e1

For detailed patch information, see the GitHub Security Advisory. Debian users should reference the Debian LTS Announcement. NetApp customers should review the NetApp Security Advisory.

Workarounds

• According to the official advisory, there are no known workarounds for this vulnerability; upgrading to version 1.48.0 or later is the only recommended remediation
• As a defense-in-depth measure, implement strict hostname length validation at the application layer to reject hostnames exceeding 255 characters
• Deploy network segmentation to isolate services that process user-controlled hostnames from internal infrastructure
• Consider using a web application firewall (WAF) to filter requests containing excessively long hostnames

# Verify your libuv version
# For systems using pkg-config:
pkg-config --modversion libuv

# Update libuv on Debian/Ubuntu systems:
sudo apt update && sudo apt install libuv1

# For Node.js applications, update to a version that includes patched libuv:
npm update