CVE-2026-64614 in Data::Deque::Shared
Summary
by MITRE • 07/21/2026
Data::Deque::Shared versions before 0.06 for Perl create a world-readable mmap backing file and open it without O_EXCL or O_NOFOLLOW.
The segment is created in deque.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.
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Analysis
by VulDB Data Team • 07/21/2026
The vulnerability in Data::Deque::Shared versions prior to 006 stems from improper file system access controls during shared memory segment creation. This flaw resides in the deque.h implementation where the open() system call is invoked with O_RDWR|O_CREAT flags and a mode parameter of 0666. When combined with the typical default umask of 022, this results in a world-readable file with permissions set to 0644, creating a significant security exposure. The absence of O_NOFOLLOW flag creates an additional attack vector where symbolic links can be exploited to redirect file access to arbitrary locations on the filesystem. Furthermore, the lack of O_EXCL prevents the open() operation from failing if the target file already exists, allowing attackers to silently overwrite or utilize pre-existing files instead of creating new ones.
This vulnerability directly maps to CWE-732: Incorrect Permission Assignment for Critical Resource and CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization. The security implications are particularly severe in shared system environments where multiple users have access to directories like /tmp or /dev/shm, which are commonly used for inter-process communication segments. Attackers can exploit this weakness through race condition scenarios where they create pre-planted files or symbolic links at the target path before the legitimate application creates its shared memory segment. The attack methodology follows patterns consistent with the ATT&CK framework's T1055.011: Process Injection via Shared Libraries, though adapted for file system manipulation rather than process injection.
The operational impact of this vulnerability extends beyond simple information disclosure to potential privilege escalation and data manipulation attacks. Local attackers can read sensitive IPC payloads stored in the world-readable shared memory segments, potentially exposing confidential data passed between processes. The race condition aspect allows attackers to manipulate the intended file creation process, enabling them to substitute their own content for legitimate application data or redirect the segment to an attacker-controlled location entirely. This creates opportunities for man-in-the-middle attacks on inter-process communications and can compromise the integrity of applications relying on this shared memory mechanism for data exchange.
Mitigation strategies should focus on implementing proper file system access controls during shared memory segment initialization. The recommended approach involves using O_EXCL flag to ensure exclusive creation of the backing file, combined with appropriate file permissions that do not grant world-read access. Additionally, the implementation should include explicit checks for symbolic links using lstat() before opening files, or better yet, use more secure temporary file creation methods such as mkstemp() which automatically handle race condition prevention and proper permission setting. Organizations should also consider restricting the use of shared memory segments in insecure locations like /tmp and instead utilize properly secured directories with appropriate access controls. The patch for this vulnerability should ensure that all file creation operations in the Data::Deque::Shared module properly enforce exclusive creation semantics and restrictive file permissions to prevent unauthorized access to shared memory contents.