CVE-2022-25147: Apache APR-util Buffer Overflow Flaw

CVE-2022-25147 Overview

CVE-2022-25147 is an Integer Overflow or Wraparound vulnerability affecting the apr_base64 functions within Apache Portable Runtime Utility (APR-util). This vulnerability allows an attacker to write beyond the bounds of a buffer, potentially leading to memory corruption and application instability.

APR-util is a widely-used companion library to the Apache Portable Runtime (APR), providing additional utility functions including Base64 encoding/decoding, database connectivity, and cryptographic routines. The library is extensively used by the Apache HTTP Server and numerous other applications that require portable runtime services.

Critical Impact

Successful exploitation of this integer overflow vulnerability could enable attackers to corrupt memory by writing data beyond allocated buffer boundaries, potentially causing denial of service or enabling further exploitation.

Affected Products

• Apache Portable Runtime Utility (APR-util) version 1.6.1
• Apache Portable Runtime Utility (APR-util) prior versions to 1.6.1
• Applications and servers utilizing vulnerable APR-util versions (including Apache HTTP Server deployments)

Discovery Timeline

• 2023-01-31 - CVE CVE-2022-25147 published to NVD
• 2025-02-13 - Last updated in NVD database

Technical Details for CVE-2022-25147

Vulnerability Analysis

The vulnerability resides in the apr_base64 functions of APR-util, which are responsible for encoding and decoding Base64 data. An integer overflow condition occurs when processing specially crafted input, causing the calculated buffer size to wrap around to a smaller-than-expected value. This miscalculation leads to allocation of an insufficient buffer, which is subsequently overflowed when the actual data is written.

The vulnerability can be exploited over the network without requiring authentication or user interaction. While the vulnerability does not directly compromise confidentiality, it can affect both integrity and availability of affected systems through unauthorized memory writes and potential application crashes.

Root Cause

The root cause of CVE-2022-25147 is improper handling of integer arithmetic in the buffer size calculations within the apr_base64 functions. When processing input of specific sizes, the multiplication or addition operations used to compute the required buffer size can exceed the maximum value representable by the integer type, causing the value to wrap around to a much smaller number (CWE-190: Integer Overflow or Wraparound).

This results in:

1. Allocation of a buffer that is too small to hold the decoded output
2. Subsequent write operations exceeding the allocated buffer boundaries
3. Potential heap or stack corruption depending on the allocation context

Attack Vector

The attack vector for this vulnerability is network-based, requiring no authentication or special privileges. An attacker can exploit this vulnerability by sending a maliciously crafted Base64-encoded payload to an application that uses the vulnerable APR-util functions for decoding. The attack complexity is low, making it relatively straightforward to trigger.

Potential attack scenarios include:

• Sending crafted HTTP requests to Apache HTTP Server installations using vulnerable APR-util
• Targeting custom applications that expose Base64 decoding functionality via network interfaces
• Exploiting backend services that process Base64-encoded data from untrusted sources

The vulnerability mechanism involves crafting input that triggers the integer overflow during buffer size calculation. When the apr_base64_decode or related functions process this input, the calculated buffer size wraps to a smaller value due to integer overflow. The subsequent decoding operation then writes beyond the allocated buffer boundaries, corrupting adjacent memory. For detailed technical information, refer to the Apache Thread Discussion.

Detection Methods for CVE-2022-25147

Indicators of Compromise

• Application crashes or unexpected terminations in services using APR-util for Base64 operations
• Memory corruption errors or segmentation faults in Apache HTTP Server or related applications
• Abnormally large or malformed Base64-encoded data in incoming network traffic
• Heap corruption signatures detected by memory safety tools or runtime protections

Detection Strategies

• Monitor for unusual application behavior including crashes, memory errors, and unexpected restarts in services using APR-util
• Implement intrusion detection rules to identify anomalously large or crafted Base64 payloads in HTTP requests
• Deploy memory corruption detection tools and address sanitizers during development and testing
• Conduct regular vulnerability scanning to identify systems running APR-util version 1.6.1 or earlier

Monitoring Recommendations

• Enable verbose logging on Apache HTTP Server and applications using APR-util to capture potential exploitation attempts
• Implement network traffic analysis to detect patterns consistent with buffer overflow exploitation
• Configure crash reporting and core dump analysis to identify potential exploitation activity
• Monitor system memory utilization for anomalies that may indicate exploitation attempts

How to Mitigate CVE-2022-25147

Immediate Actions Required

• Identify all systems and applications using Apache Portable Runtime Utility (APR-util) version 1.6.1 or earlier
• Prioritize patching of internet-facing systems, particularly Apache HTTP Server deployments
• Review and restrict network access to services that process Base64-encoded data where possible
• Consider implementing Web Application Firewall (WAF) rules to filter potentially malicious Base64 payloads

Patch Information

Apache has addressed this vulnerability in newer versions of APR-util. Organizations should upgrade to the latest patched version of APR-util to remediate this vulnerability. Refer to the Apache Thread Discussion for official patch information and guidance.

For NetApp product users, consult the NetApp Security Advisory NTAP-20240315-0001 for product-specific patching guidance.

Workarounds

• Implement input validation to restrict the size of Base64-encoded data processed by applications
• Deploy network-level filtering to block abnormally large Base64 payloads before they reach vulnerable services
• Use application-level rate limiting to mitigate potential denial of service impacts
• Consider isolating vulnerable services using network segmentation until patches can be applied

# Configuration example - Input size limiting for Apache
# Add to Apache configuration to limit request body size
LimitRequestBody 10485760
# Limit header fields that may contain Base64 data
LimitRequestFieldSize 8190