CVE-2026-59142: Data::HashMap::Shared versions before 0.14 for Perl allow an out-of-bounds read via an unvalidated arena offset and length in shm_str

Data::HashMap::Shared versions before 0.14 for Perl allow an out-of-bounds read via an unvalidated arena offset and length in shm_str_copy.

Data::HashMap::Shared versions before 0.14 for Perl allow an out-of-bounds read via an unvalidated arena offset and length in shm_str_copy. The attach-time validator shm_validate_header checks the header scalars and region layout against the file size, but does not validate the array contents it then trusts. shm_str_copy does memcpy(dst, arena + off, len) with off and len read raw from the mmap'd segment and unbounded, on the each, keys, values, pop, shift, take, swap, drain and cursor paths. The get path bounds off and len separately and is not affected. A local peer that can write the backing file can leave the header valid while poisoning a record's offset and length, so iterating or draining the map copies a file-controlled offset and length out of the arena, reading adjacent memory or crashing the process.

Description from the National Vulnerability Database, published by 9b29abf9-4ab0-4765-b253-1875cd9b441e

What it means for a small business

If your business uses Data::HashMap::Shared, install the vendor's update. If you're not sure whether you use it, ask whoever manages your computers.

How likely is an attack? The Exploit Prediction Scoring System, run by FIRST (the global association of security response teams), puts the odds of this one being exploited in the next 30 days at 0.54%, higher than 45% of CVEs. That’s low, but low isn’t zero, and the odds jump the day someone publishes an exploit. Scored October 29, 2026, updated daily.

Check your own setup

Website check: reads what your site runs from the outside (WordPress version, plugins it can see, old server software) and matches it against this database.
Server check: what your web server says about itself, and whether that version has known flaws.

Sources

Part of the Huttenlocher Technologies vulnerability database, refreshed twice a day from CISA and the NVD. The title, category and plain-language guidance are ours; check the linked record before acting on a detail. This is general guidance, not a review of your systems.

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