CVE-2026-10879: Perl DBI Buffer Overflow Vulnerability

CVE-2026-10879 Overview

CVE-2026-10879 is a heap overflow vulnerability in Perl DBI versions before 1.648. The flaw exists in the preparse method, which expands SQL placeholder characters into numbered binders of the form :pN. The function allocates only three characters per binder in its buffer, which is insufficient when binder counts reach double or triple digits. SQL statements containing more than 9 placeholders trigger an out-of-bounds heap write [CWE-787]. The Perl DBI module is the foundational database interface used by thousands of Perl applications, making the impact broad across database-connected services.

Critical Impact
A heap overflow with network attack vector and no required privileges or user interaction enables potential remote code execution against applications passing untrusted SQL through DBI->preparse.

Affected Products

Perl DBI versions prior to 1.648
Applications and frameworks linking against vulnerable DBI builds
Database-driven Perl services exposing preparse to untrusted SQL input

Discovery Timeline

2026-06-05 - CVE-2026-10879 published to NVD
2026-06-06 - Disclosure posted to the Openwall oss-security list
2026-06-10 - Last updated in NVD database

Technical Details for CVE-2026-10879

Vulnerability Analysis

The Perl DBI module provides a database-independent interface for Perl programs. The preparse method rewrites SQL placeholder characters such as ? into numbered binders formatted as :pN, where N is the placeholder index. The output buffer reserves three characters for each binder, sufficient only for indices :p1 through :p9.

When SQL contains 10 or more placeholders, binder strings expand to four characters (:p10 through :p99). Counts of 100 or more require five characters, and so on. The fixed three-character allocation produces a heap buffer overflow proportional to the number of placeholders beyond nine.

The vulnerability is classified as an out-of-bounds write [CWE-787]. Heap overflows of this type can corrupt adjacent heap metadata or function pointers, enabling memory corruption that may escalate to arbitrary code execution under the privileges of the Perl process.

Root Cause

The root cause is a static per-binder allocation in the preparse buffer sizing logic. The implementation assumed single-digit placeholder indices and did not scale the buffer to account for variable-width numeric expansions. The patch in commit af79036c07aa9a457971c0f4136e37c85dc20978 corrects buffer sizing to accommodate any placeholder count.

Attack Vector

The vulnerability is reachable over the network where applications accept SQL fragments or query templates from untrusted sources and pass them to DBI->preparse. An attacker submits a crafted SQL string containing many placeholder characters to trigger the overflow. The vulnerability requires no authentication and no user interaction.

The preparse flow is described in the MetaCPAN Release Changes and the Openwall OSS Security Post.

Detection Methods for CVE-2026-10879

Indicators of Compromise

Crash signatures or SIGSEGV events in Perl processes invoking DBIpreparse operations
Database driver logs showing unusually long or malformed SQL with 10 or more ? placeholders from untrusted callers
Unexpected child processes spawned by Perl interpreters running database workloads

Detection Strategies

Inventory installed Perl DBI versions across servers and developer workstations using perl -MDBI -e 'print $DBI::VERSION'
Static-scan Perl source repositories for calls to DBI->preparse that accept caller-controlled SQL
Monitor web application firewalls and application logs for SQL inputs containing high placeholder counts

Monitoring Recommendations

Alert on Perl process crashes in production database tiers and capture core dumps for triage
Track outbound network connections initiated by Perl interpreters that normally only speak to local databases
Correlate request payload sizes with downstream errors to identify exploit attempts against preparse

How to Mitigate CVE-2026-10879

Immediate Actions Required

Upgrade Perl DBI to version 1.648 or later on all systems
Identify and patch container images, build artifacts, and vendored Perl bundles that ship older DBI
Restrict untrusted input from reaching DBI->preparse until patching completes

Patch Information

The fix is published in DBI 1.648 on CPAN. The upstream change is available as the GitHub Commit Patch. Distribution maintainers should rebuild Perl packages depending on DBI and redeploy.

Workarounds

Avoid calling DBI->preparse on SQL containing user-controlled placeholder counts
Validate and reject SQL inputs exceeding a strict placeholder threshold at the application boundary
Use parameterized queries via prepare and execute rather than constructing SQL fragments for preparse

bash

# Upgrade DBI via CPAN
cpanm DBI@1.648

# Verify installed version
perl -MDBI -e 'print "DBI version: $DBI::VERSION\n"'