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CVE-2026-65066 EGOR CVE debrief

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. This allows any local user to read the IPC payloads stored in the shared segment.

Vendor
EGOR
Product
Data::RingBuffer::Shared
CVSS
Unknown
CISA KEV
Not listed in stored evidence
Original CVE published
2026-07-21
Original CVE updated
2026-07-22
Advisory published
2026-07-21
Advisory updated
2026-07-22

Who should care

Users of Data::RingBuffer::Shared versions before 0.04 for Perl, especially those with shared directories such as /tmp or /dev/shm, should be aware of the potential for local attackers to read IPC payloads or win a pre-creation race. Affected operators, platforms, and security teams should review the vulnerability and take necessary actions to mitigate the risk.

Technical summary

The Data::RingBuffer::Shared module for Perl creates a world-readable mmap backing file due to a missing O_EXCL and O_NOFOLLOW flags when opening the file. Specifically, the file is created with open(path, O_RDWR|O_CREAT, 0666), resulting in a file mode of 0644 (world-readable) under the default umask 022. This allows any local user to read the IPC payloads stored in the shared segment. Additionally, the absence of O_NOFOLLOW allows a symlink planted at the path to be followed, and the absence of O_EXCL allows the open to silently use a pre-planted file instead of failing.

Defensive priority

High

Recommended defensive actions

  • Update to Data::RingBuffer::Shared version 0.04 or later
  • Use O_EXCL and O_NOFOLLOW flags when opening the mmap backing file
  • Restrict access to shared directories such as /tmp or /dev/shm
  • Monitor for suspicious activity in shared directories
  • Review compensating controls for exposed systems while remediation is scheduled and verified
  • Check relevant monitoring, detection, and logs for exposed assets that need extra review
  • Track exceptions, retest remediated assets, and close the item only after evidence is documented

Evidence notes

The CVE record was published on 2026-07-21T20:17:05.637Z and has not been modified since then. The NVD entry is currently Deferred. There is limited information available about the vulnerability, and defenders should verify the affected scope and severity with the vendor. The Data::RingBuffer::Shared module for Perl creates a world-readable mmap backing file due to a missing O_EXCL and O_NOFOLLOW flags when opening the file.

Official resources

AI-assisted PatchSiren debrief based on the supplied source corpus. The CVE record was published on 2026-07-21T20:17:05.637Z and has not been modified since then. The NVD entry is currently Deferred.