CVE-2026-59144: Perl RingBuffer Buffer Overflow Flaw

CVE-2026-59144 Overview

CVE-2026-59144 is a stack buffer overflow [CWE-121] affecting the Perl module Data::RingBuffer::Shared in versions before 0.04. The flaw resides in the ring_read_seq function, which copies data from a memory-mapped ring buffer into a fixed 8-byte scalar destination. The attach-time validator ring_validate_header never caps the elem_size field against the destination size, allowing a memcpy to write beyond the destination buffer. A local peer with write access to the backing file can craft a header that passes validation while specifying a large elem_size, corrupting adjacent stack frames on the next read.

Critical Impact
A local peer with write access to the shared backing file can corrupt the reader's stack and achieve arbitrary code execution in the context of the consuming Perl process.

Affected Products

Data::RingBuffer::Shared for Perl, versions prior to 0.04
Perl applications that consume shared ring buffers produced by untrusted local peers
Systems distributing the Data-RingBuffer-Shared CPAN distribution by author EGOR

Discovery Timeline

2026-07-21 - CVE-2026-59144 published to the National Vulnerability Database (NVD)
2026-07-22 - Last updated in NVD database

Technical Details for CVE-2026-59144

Vulnerability Analysis

The vulnerability affects the C-level ring buffer implementation shipped with the Data::RingBuffer::Shared Perl module. The module maps a shared file segment containing a header and a slot array, then exposes read and write primitives to Perl. On attach, ring_validate_header inspects the header for capacity overflow and confirms consistency between total_size and other header fields. The check is incomplete: it never validates that elem_size fits the destination scalar used by the reader.

The reading path ring_read_seq performs memcpy(out, ring_slot(h, seq), elem_size), where out points to a fixed 8-byte stack scalar and elem_size is read verbatim from the shared segment. Any elem_size greater than 8 writes past the destination and into adjacent stack frames. Because the source data and length both originate from a peer-writable file, the attacker controls both the length of the overflow and the bytes copied.

Root Cause

The root cause is missing input validation on the elem_size field of the ring buffer header. The validator confirms structural consistency but does not enforce a maximum against the reader's fixed 8-byte destination. This is a classic stack-based buffer overflow [CWE-121] driven by an unchecked length taken from untrusted shared memory.

Attack Vector

Exploitation requires a local peer with write access to the memory-mapped backing file used by Data::RingBuffer::Shared. The attacker writes a header that satisfies ring_validate_header while setting a large elem_size, then places controlled payload bytes in the slot region. When the victim process next calls ring_read_seq, the memcpy writes the attacker-controlled bytes into the reader's stack frame. Overwriting saved return addresses or frame pointers enables arbitrary code execution in the reader's process context. See the MetaCPAN Release Diff for the specific header handling changes introduced in the fix.

Detection Methods for CVE-2026-59144

Indicators of Compromise

Unexpected crashes, segmentation faults, or stack canary violations in Perl processes that load Data::RingBuffer::Shared.
Backing files used by the module showing elem_size header fields larger than the expected slot payload size.
Local user accounts with write access to shared ring buffer files owned or read by higher-privileged Perl services.

Detection Strategies

Inventory installed CPAN distributions and flag any Data-RingBuffer-Shared release earlier than 0.04.
Statically inspect ring buffer backing files for anomalous elem_size values before consumption in production pipelines.
Enable core dump collection and stack canary reporting for Perl services to surface exploitation attempts.

Monitoring Recommendations

Audit file system access control lists on shared ring buffer segments and alert on writes from unexpected user IDs.
Monitor process telemetry for Perl interpreters spawning unexpected child processes or shells after reads from shared memory files.
Track CPAN module versions across hosts and alert when vulnerable versions of Data::RingBuffer::Shared are present.

How to Mitigate CVE-2026-59144

Immediate Actions Required

Upgrade Data::RingBuffer::Shared to version 0.04 or later on all systems that consume the module.
Restrict write permissions on ring buffer backing files to a single trusted producer identity.
Restart Perl services after upgrading to ensure the patched module is loaded into memory.

Patch Information

The maintainer released Data::RingBuffer::Shared version 0.04 with a fix that validates elem_size against the destination size in the reader path. Review the MetaCPAN Release Changes and the MetaCPAN Release Diff for the exact code changes to ring.h.

Workarounds

Place ring buffer backing files on file systems only writable by the producing process and mount consumer views read-only where possible.
Wrap consumer reads with an application-level check that rejects headers whose elem_size exceeds the expected slot payload size.
Isolate Perl consumers of shared ring buffers in dedicated, unprivileged containers to limit the blast radius of a stack corruption.

bash

# Configuration example: upgrade the vulnerable module via cpanm
cpanm Data::RingBuffer::Shared@0.04

# Restrict write access on the backing file to the producer only
chown producer:producer /var/run/ringbuf.dat
chmod 0640 /var/run/ringbuf.dat