CVE-2017-20230: Nwclark Storable Buffer Overflow Flaw

CVE-2017-20230 Overview

CVE-2017-20230 is a stack overflow vulnerability affecting the Storable module for Perl prior to version 3.05. The vulnerability exists in the retrieve_hook function, where an integer signedness mismatch allows attackers to craft malicious data that triggers a stack overflow condition.

Critical Impact

This vulnerability can be exploited remotely without authentication to potentially achieve arbitrary code execution or cause denial of service conditions on systems processing untrusted Storable data.

Affected Products

• nwclark storable (versions before 3.05)
• Perl distributions bundling vulnerable Storable module
• Applications using Storable for serialization/deserialization

Discovery Timeline

• 2026-04-21 - CVE CVE-2017-20230 published to NVD
• 2026-04-22 - Last updated in NVD database

Technical Details for CVE-2017-20230

Vulnerability Analysis

The vulnerability resides in the retrieve_hook function within the Storable module. The core issue stems from an integer signedness mismatch: the function stores the length of a class name into a signed integer variable, but subsequent read operations treat this length value as unsigned. This type confusion creates a scenario where an attacker can provide a specially crafted negative value that, when interpreted as an unsigned integer, results in an extremely large value being used for memory operations.

When processing maliciously crafted serialized data, this integer signedness error leads to a stack-based buffer overflow (CWE-121). The overflow occurs because the function allocates stack space based on the signed interpretation but then performs read operations based on the unsigned interpretation, causing data to be written beyond the allocated stack buffer boundaries.

Root Cause

The root cause is an integer signedness error in the retrieve_hook function. The class name length parameter is stored in a signed integer type, but memory read operations interpret this value as unsigned. When a negative value is provided, the signed-to-unsigned conversion results in an unexpectedly large positive number, causing excessive data to be read onto the stack and triggering the overflow condition.

Attack Vector

The attack can be performed over the network by supplying maliciously crafted Storable-serialized data to an application that deserializes untrusted input. The attacker constructs serialized data containing a negative class name length value. When the vulnerable Storable module processes this data, the signed integer is interpreted as a large unsigned value during read operations, causing stack memory corruption.

The exploitation flow involves:

1. Attacker creates malicious serialized data with a crafted negative length field
2. Target application receives and attempts to deserialize the data using Storable
3. The retrieve_hook function processes the class name length as signed, then as unsigned
4. Stack overflow occurs, potentially allowing code execution or causing a crash

Detection Methods for CVE-2017-20230

Indicators of Compromise

• Unexpected crashes in Perl applications processing serialized data with stack overflow signatures
• Application segmentation faults originating from Storable module operations
• Anomalous memory access patterns in processes using the retrieve_hook function
• Unusually large or malformed serialized data payloads targeting Perl applications

Detection Strategies

• Monitor for Perl process crashes with stack-related error messages
• Implement input validation on serialized data before deserialization
• Use application-level logging to track Storable deserialization operations on untrusted data
• Deploy runtime application self-protection (RASP) to detect memory corruption attempts

Monitoring Recommendations

• Enable verbose logging for applications that deserialize external Storable data
• Set up alerting for repeated crashes or restarts of Perl-based services
• Monitor system logs for segfaults in processes using the Storable module
• Track network traffic for anomalous serialized data patterns

How to Mitigate CVE-2017-20230

Immediate Actions Required

• Upgrade Storable module to version 3.05 or later immediately
• Audit applications to identify any processing of untrusted serialized Storable data
• Implement input validation to reject malformed or suspicious serialized data
• Consider temporarily disabling deserialization of external data until patching is complete

Patch Information

A patch addressing this vulnerability has been released. Users should upgrade to Storable version 3.05 or later to remediate this issue. The official patch is available through the GitHub Perl Patch. Additional details about the fix can be found in GitHub Issue #15831 and the MetaCPAN Release Changes.

Workarounds

• Avoid deserializing Storable data from untrusted sources until patching is possible
• Implement strict input validation and size checks on incoming serialized data
• Use alternative serialization formats (JSON, YAML) for processing external data
• Deploy network-level filtering to block known malicious payload patterns

# Upgrade Storable to patched version
cpan install Storable

# Verify installed version
perl -MStorable -e 'print $Storable::VERSION . "\n"'

# Ensure version is 3.05 or higher