CVE-2026-88816 in DBI
Summary
by MITRE • 09/28/2026
DBI versions before 1.654 for Perl incorrectly treat numeric values as strings in FetchHashKeyName.
fetchrow_hashref uses the string pointer of the FetchHashKeyName attribute as the key name without stringifying it first. When FetchHashKeyName has been set to an integer (IV) or floating-point (NV) value, that pointer is invalid, so reading the key name triggers a segmentation fault.
This can be triggered with the following code:
my $dbh = DBI->connect( "dbi:ExampleP:", "", "", { RaiseError => 0, PrintError => 0 } );
$dbh->{FetchHashKeyName} = 42;
my $sth = $dbh->prepare("select mode, size, name from ."); $sth->execute; $sth->fetchrow_hashref;
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Analysis
by VulDB Data Team • 09/28/2026
The vulnerability identified in Perl DBI versions prior to 1.654 represents a critical memory safety flaw within the FetchHashKeyName attribute handling mechanism. This issue stems from an incorrect type coercion and pointer management error where numeric values are treated as valid string pointers without proper conversion or validation. In the context of database interaction, the fetchrow_hashref function is responsible for retrieving rows from a result set and returning them as hash references. The keys of these hashes are determined by the FetchHashKeyName attribute, which dictates whether column names should be used, their indices, or other identifiers. When this attribute is misconfigured with a numeric value rather than a valid string reference, the underlying C implementation fails to perform necessary type checking or conversion before dereferencing the pointer.
The technical root cause lies in how Perl handles internal variable types and memory addresses during function calls. In older versions of DBI, when FetchHashKeyName was set to an integer (IV) or floating-point number (NV), the code attempted to use this numeric value directly as a string pointer for hash key generation. Since integers and floats are stored differently in memory compared to strings, treating them as pointers leads to accessing invalid memory addresses. This results in a segmentation fault when the application attempts to read from these corrupted pointers during the execution of fetchrow_hashref. The vulnerability is particularly insidious because it requires specific configuration by the developer or user but can be triggered remotely if input data influences database query parameters that subsequently affect internal state management, although typically this involves local code misconfiguration rather than direct external exploitation via network inputs alone.
From an operational perspective, this flaw leads to immediate application crashes and denial of service conditions for any Perl-based web applications or backend services utilizing the affected DBI versions. If a server process running under a specific user account terminates unexpectedly due to segmentation faults, it can disrupt ongoing transactions, leave database connections in inconsistent states, and potentially expose sensitive information through error logs if not properly sanitized. Furthermore, repeated crashes may indicate instability that could be leveraged for more sophisticated attacks such as timing analysis or resource exhaustion if the application attempts automatic restarts without proper safeguards. The impact is severe because it compromises availability and integrity of data processing pipelines dependent on reliable database interactions.
Mitigation strategies primarily involve upgrading to DBI version 1.654 or later, where this type handling issue has been resolved through improved input validation and safe pointer management practices. Developers should also implement defensive coding techniques by validating the FetchHashKeyName attribute before assignment, ensuring it is always set to a valid string value such as NAME_lc, NAME_uc, or INDEX depending on requirements. Additionally, enabling strict mode in Perl scripts can help catch type mismatches early during development phases rather than at runtime. For environments where immediate patching is not feasible, implementing wrapper functions that sanitize database handle attributes before passing them to DBI methods provides an additional layer of protection against accidental misconfiguration leading to crashes.
This vulnerability aligns with CWE-125 Out-of-bounds Read and CWE-476 NULL Pointer Dereference categories within the Common Weakness Enumeration framework due to improper handling of memory references derived from incorrect type assumptions. It also relates to ATT&CK technique T1089 Disabling or Modifying Security Software indirectly, as crashing security monitoring agents running Perl scripts could hinder detection capabilities if those agents rely on stable database connectivity for logging events. Understanding these classifications helps organizations prioritize remediation efforts based on standardized risk assessment models while ensuring compliance with best practices for secure software development lifecycle management.