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CVE-2026-59144                                       CPAN Security Group
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         CVE ID:  CVE-2026-59144
   Distribution:  Data-RingBuffer-Shared
       Versions:  before 0.04

       MetaCPAN:  https://metacpan.org/dist/Data-RingBuffer-Shared
       VCS Repo: https://github.com/vividsnow/perl5-data-ringbuffer-shared

Data::RingBuffer::Shared versions before 0.04 for Perl allow a stack
buffer overflow via an unvalidated elem_size in ring_read_seq

Description
-----------
Data::RingBuffer::Shared versions before 0.04 for Perl allow a stack
buffer overflow via an unvalidated elem_size in ring_read_seq.

The attach-time validator ring_validate_header checks the
capacity-overflow and total_size consistency of the header but never
caps elem_size against the destination size. ring_read_seq does
memcpy(out, ring_slot(h, seq), elem_size) with elem_size read raw from
the mmap'd segment, copying into a fixed 8-byte destination scalar. An
elem_size larger than 8 bytes writes past the destination.

A local peer that can write the backing file can leave the header valid
while setting a large elem_size, so the next read copies a
file-controlled length into the fixed 8-byte stack buffer, corrupting
adjacent stack frames.

Problem types
-------------
- CWE-121 Stack-based Buffer Overflow

Workarounds
-----------
For deployments that cannot upgrade to 0.04, place the backing file in
a directory writable only by the owning user, so a local peer cannot
tamper with the elem_size the read path trusts.

Solutions
---------
Upgrade to Data::RingBuffer::Shared 0.04 or later, which pins elem_size
to the fixed element size of the buffer's registered variant.

References
----------
https://metacpan.org/release/EGOR/Data-RingBuffer-Shared-0.04/diff/EGOR/Data-RingBuffer-Shared-0.03#ring.h
https://metacpan.org/release/EGOR/Data-RingBuffer-Shared-0.04/changes