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CVE-2026-65066                                       CPAN Security Group
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         CVE ID:  CVE-2026-65066
   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 create a
world-readable mmap backing file and open it without O_EXCL or
O_NOFOLLOW

Description
-----------
Data::RingBuffer::Shared versions before 0.04 for Perl create a
world-readable mmap backing file and open it without O_EXCL or
O_NOFOLLOW.

The segment is created in ring.h with open(path, O_RDWR|O_CREAT, 0666).
The mode is 0666, so under the default umask 022 the file is created
mode 0644 (world-readable). O_NOFOLLOW is absent, so a symlink planted
at the path is followed, and O_EXCL is absent, so the open silently
uses a pre-planted file instead of failing.

A "Shared" segment naturally lives in a shared directory such as /tmp
or /dev/shm, where any local user can read the IPC payloads stored in
the world-readable segment, and a pre-planted file or symlink at the
path lets a local attacker win a pre-creation race or redirect the
open.

Problem types
-------------
- CWE-732 Incorrect Permission Assignment for Critical Resource
- CWE-59 Improper Link Resolution Before File Access

Workarounds
-----------
For deployments that cannot upgrade to 0.04, set a restrictive umask so
the backing file is not world-readable and place it in a directory only
the owning user can access.

Solutions
---------
Upgrade to Data::RingBuffer::Shared 0.04 or later, which creates the
backing file mode 0600 (owner-only) with O_EXCL and O_NOFOLLOW.

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