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CVE-2026-64613                                       CPAN Security Group
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         CVE ID:  CVE-2026-64613
   Distribution:  Data-Buffer-Shared
       Versions:  before 0.05

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

Data::Buffer::Shared versions before 0.05 for Perl create a
world-readable mmap backing file and open it without O_NOFOLLOW

Description
-----------
Data::Buffer::Shared versions before 0.05 for Perl create a
world-readable mmap backing file and open it without O_NOFOLLOW.

The segment is created in buf_generic.h with open(path,
O_RDWR|O_CREAT|O_EXCL, 0666). O_EXCL blocks a pre-seeded file on
create, but the mode is 0666, so under the default umask 022 the file
is created mode 0644 (world-readable), and O_NOFOLLOW is absent, so a
symlink planted at the path is followed when the segment is attached.

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 symlink at the path
redirects the open to another file.

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 0.05, 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::Buffer::Shared 0.05 or later, which creates the
backing file mode 0600 (owner-only) with O_NOFOLLOW.

References
----------
https://metacpan.org/release/EGOR/Data-Buffer-Shared-0.05/diff/EGOR/Data-Buffer-Shared-0.04#buf_generic.h
https://metacpan.org/release/EGOR/Data-Buffer-Shared-0.05/changes