CVE-2020-10543: Perl Buffer Overflow Vulnerability

CVE-2020-10543 Overview

CVE-2020-10543 is a heap-based buffer overflow vulnerability affecting Perl versions before 5.30.3 on 32-bit platforms. The vulnerability arises from an integer overflow condition when processing nested regular expression quantifiers. When a malicious or malformed regular expression with deeply nested quantifiers is processed, the integer overflow leads to incorrect memory allocation size calculations, subsequently causing a heap-based buffer overflow that can result in denial of service or potentially arbitrary code execution.

Critical Impact

This vulnerability allows remote attackers to trigger a heap-based buffer overflow through crafted regular expressions on 32-bit Perl installations, potentially causing application crashes or enabling code execution in applications that process untrusted input patterns.

Affected Products

• Perl versions before 5.30.3 on 32-bit platforms (x86)
• Fedora 31
• openSUSE Leap 15.1
• Oracle Communications Billing and Revenue Management 12.0.0.2.0 and 12.0.0.3.0
• Oracle Communications Diameter Signaling Router
• Oracle Communications Eagle Application Processor
• Oracle Communications Eagle LNP Application Processor (versions 10.1, 10.2, 46.7, 46.8, 46.9)
• Oracle Communications LSMS
• Oracle Communications Offline Mediation Controller 12.0.0.3.0
• Oracle Communications Performance Intelligence Center
• Oracle Communications Pricing Design Center 12.0.0.3.0
• Oracle Configuration Manager 12.1.2.0.8
• Oracle Enterprise Manager Base Platform 13.4.0.0
• Oracle SD-WAN Edge (versions 8.2, 9.0, 9.1)
• Oracle Tekelec Platform Distribution

Discovery Timeline

• June 5, 2020 - CVE-2020-10543 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2020-10543

Vulnerability Analysis

This vulnerability is classified as CWE-190 (Integer Overflow or Wraparound). The flaw exists specifically within the regular expression engine of Perl when running on 32-bit architectures. When processing nested quantifiers in regular expressions (such as patterns with multiple nested *, +, or {n,m} constructs), the regex engine performs calculations to determine required memory allocation. On 32-bit platforms, these calculations can overflow the integer bounds, resulting in an allocation that is significantly smaller than required.

The heap-based buffer overflow occurs when the regex engine subsequently writes data into the undersized buffer, corrupting heap memory structures. This can lead to application crashes, denial of service, or in sophisticated attack scenarios, could potentially be leveraged for arbitrary code execution depending on the heap layout and application behavior.

The vulnerability is exploitable remotely in scenarios where Perl applications accept and process regular expression patterns from untrusted sources, such as web applications, log parsers, or data validation tools running on 32-bit systems.

Root Cause

The root cause is an integer overflow vulnerability in the calculation logic for memory allocation when processing deeply nested regular expression quantifiers. On 32-bit platforms, the multiplication operations used to calculate the total memory requirements for regex compilation can exceed the maximum value of a 32-bit integer, wrapping around to a small value. This causes malloc() to allocate an insufficient buffer, which is then overwritten during regex compilation.

Attack Vector

The attack vector is network-based, requiring no authentication or user interaction. An attacker can exploit this vulnerability by:

1. Identifying a Perl application running on a 32-bit platform that processes user-supplied regular expressions or input matched against complex regex patterns
2. Crafting a malicious input containing deeply nested regex quantifiers designed to trigger the integer overflow
3. Submitting this payload to the vulnerable application

The crafted regular expression triggers the integer overflow during compilation, causing the undersized heap allocation and subsequent buffer overflow when the regex engine writes pattern data. Applications that use Perl for CGI processing, data validation, log analysis, or any text processing with regex on 32-bit systems are potential targets.

The vulnerability exploits nested quantifier structures that multiply memory requirements exponentially. When these nested constructs exceed the calculation bounds on 32-bit integer arithmetic, the overflow occurs silently without proper bounds checking, leading to heap corruption during regex compilation.

Detection Methods for CVE-2020-10543

Indicators of Compromise

• Unexpected Perl process crashes or segmentation faults during regex processing operations
• Abnormal heap memory patterns or corruption detected in application crash dumps
• Input containing unusually complex nested regular expression patterns (multiple levels of quantifier nesting)
• Application logs showing regex compilation failures or memory allocation errors

Detection Strategies

• Deploy application-level monitoring to detect malformed or overly complex regular expression patterns in user input
• Implement memory corruption detection tools (such as AddressSanitizer or Valgrind) during testing to identify heap overflow conditions
• Monitor Perl application resource usage for anomalous memory allocation patterns
• Use SentinelOne's behavioral analysis to detect exploitation attempts targeting memory corruption vulnerabilities

Monitoring Recommendations

• Enable core dump analysis for Perl applications to capture crash details that may indicate exploitation attempts
• Monitor system logs for unexpected Perl interpreter terminations or error messages related to memory allocation
• Implement input validation logging to track regex patterns submitted to applications for forensic analysis
• Configure alerting on rapid succession of Perl process crashes which may indicate active exploitation

How to Mitigate CVE-2020-10543

Immediate Actions Required

• Upgrade Perl to version 5.30.3 or later on all affected 32-bit systems
• Apply vendor patches from Oracle, Fedora, openSUSE, and other affected distributions as available
• Review and validate all Perl-based applications that process untrusted regular expressions
• Consider migrating critical applications from 32-bit to 64-bit platforms where feasible

Patch Information

The vulnerability has been addressed in Perl version 5.30.3. The fix is available in commit 897d1f7fd515b828e4b198d8b8bef76c6faf03ed in the Perl5 repository. Detailed release notes are available in the Perl 5.30.3 Delta documentation.

Multiple vendors have released updates addressing this vulnerability:

• Oracle October 2020 Security Alert
• Oracle January 2021 Security Alert
• Oracle April 2021 Security Alert
• Fedora Package Announcement
• Gentoo GLSA 202006-03
• NetApp Security Advisory

Workarounds

• Implement input validation to reject or sanitize regular expression patterns before processing, limiting nesting depth and complexity
• Run Perl applications in isolated containers or sandboxes to limit the impact of potential exploitation
• Consider using 64-bit platforms where possible, as this vulnerability specifically affects 32-bit architectures
• Apply network-level controls to restrict access to applications that process regex patterns from untrusted sources

# Check current Perl version to verify if vulnerable
perl -v | grep version

# For systems using package managers, update Perl:
# On Fedora/RHEL:
sudo dnf update perl

# On openSUSE:
sudo zypper update perl

# On Debian/Ubuntu:
sudo apt-get update && sudo apt-get upgrade perl