CVE-2026-65061 in Data::ReqRep::Shared
Summary
by MITRE • 07/21/2026
Data::ReqRep::Shared versions before 0.05 for Perl create a world-readable mmap backing file and open it without O_EXCL or O_NOFOLLOW.
The segment is created in reqrep.h with open(path, O_RDWR | O_CREAT, 0666), for both the request-reply and the integer-variant segments. 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 Data::ReqRep::Shared Perl module vulnerability stems from improper file creation handling that exposes sensitive inter-process communication data to unauthorized access. This flaw exists in versions prior to 005 and fundamentally compromises the security of shared memory segments used for request-reply communications. The vulnerability manifests through the open() system call implementation in reqrep.h where files are created with inadequate permission controls and security checks. The module creates memory-mapped files using open(path, O_RDWR | O_CREAT, 0666) which establishes world-readable permissions by default, as the 0666 mode combined with typical umask 022 results in 0644 permissions allowing all users to read the file contents. This represents a direct violation of principle of least privilege and information hiding principles that should govern shared memory segments containing potentially sensitive data.
The technical implementation flaw extends beyond simple permission issues to include critical missing security flags that enable various attack vectors. The absence of O_NOFOLLOW flag creates symlink traversal vulnerabilities where an attacker can place a symbolic link at the target path before the legitimate process creates the file, causing the application to open and write to the attacker-controlled target instead of the intended location. Additionally, the lack of O_EXCL flag allows silent overwrite operations when files already exist at the specified path, enabling attackers to pre-create files with malicious content or manipulate existing segments. These missing flags directly correlate to CWE-362 (Concurrent Execution using Shared Resources) and CWE-73 (External Control of File Name or Path) categories in the Common Weakness Enumeration framework, representing multiple security misconfigurations that together create a dangerous attack surface.
The operational impact of this vulnerability extends beyond simple information disclosure to include potential data manipulation and system compromise scenarios. In shared directories like /tmp or /dev/shm, where any local user can access files, the world-readable nature of these segments means that sensitive IPC payloads become accessible to all local users on the system. Attackers can exploit the race condition inherent in the pre-creation scenario by establishing malicious files or symlinks before legitimate processes create their own segments. This creates opportunities for data injection attacks where an attacker can manipulate communication data between processes, potentially leading to privilege escalation or information leakage that violates confidentiality requirements defined in security standards such as NIST SP 800-53. The vulnerability affects the integrity and confidentiality of inter-process communications, making it particularly dangerous in environments where sensitive data flows through these shared memory segments.
Mitigation strategies for this vulnerability must address both the immediate implementation flaws and broader architectural security concerns. The most direct fix involves modifying the open() call to include proper security flags such as O_EXCL to prevent silent overwrites and O_NOFOLLOW to prevent symlink traversal attacks. Additionally, file permissions should be restricted from 0666 to more restrictive modes like 0600 or 0640 to limit access to only authorized processes. The module should also implement proper directory validation and ensure that shared memory segments are created in secure locations with appropriate access controls rather than relying on default system directories. Organizations should consider implementing the ATT&CK technique T1553.002 (Subvert Trust Controls: Code Signing) through proper file integrity monitoring to detect unauthorized modifications to these shared segments. System administrators should also review and restrict access to shared directories like /tmp and /dev/shm, ensuring that only legitimate processes can create files in these locations and implementing proper privilege separation mechanisms to minimize the impact of potential exploitation attempts.