External risk intelligence

Data::HashMap::Shared Out-of-Bounds Read via Unvalidated Offset

CVE advisorySeverity: CRITICAL (CVSS 9.1)

CVE-2026-59142

The vulnerability exists in a Perl module used for shared memory operations. It requires a local peer to have write access to a specific backing file to manipulate the shared memory segment. It is not an internet-facing service or protocol and typically operates within the local context of the application's memory management.

Out-of-bounds Read

Halo Surface Signal: 1 out of 5 — much less likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

This CVE concerns a vulnerability in a Perl module that handles shared memory, potentially allowing unauthorized memory access or process crashes if an attacker can modify a specific backing file. The main concern is confirming relevance and exposure within our specific technology stack.

Reads memory outside its intended area.
Matters for local file manipulation risks.
Confirm if this Perl module is in use.

Attack Path

How an attacker could exploit the issue

An attacker could exploit this vulnerability by manipulating a shared memory segment that a vulnerable Perl application uses. If an attacker can write to the backing file for this segment, they can tamper with data that controls how much information is read. This could allow them to read unintended data from memory or cause the application to crash.

Local write access to shared memory backing file.
Triggered by map iteration, draining, or cursor operations.
Information disclosure and denial of service.

Live Threat

Current exploitation, exposure, and threat context

When supported by the advisory, a local attacker with write access to a backing file could trigger an out-of-bounds read. This occurs when the `shm_str_copy` function, within `Data::HashMap::Shared`, processes an unvalidated offset and length from a memory-mapped segment, potentially leading to the disclosure of adjacent memory contents or a denial-of-service condition.

Reading adjacent memory.
Unvalidated offset and length.
Process crash or memory disclosure.

Operational Fix

Recommended remediation, mitigation, and detection steps

Real-world remediation will likely involve application owners and platform teams. The first practical step is to identify all instances of the affected Perl module, determine their reachability and criticality, and then confirm the accountable owner for each instance before planning remediation activities based on the assessed risk.

Application owners and platform teams.
Verify affected module and its reachability.
Plan remediation based on risk assessment.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

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Frequently asked questions

What is the Data::HashMap::Shared Perl module?

It is a Perl component designed to manage shared memory structures. Developers use it to store and retrieve data in memory segments that can be shared between processes, which is useful for high-performance applications that need to persist or exchange hash map data efficiently.

How does CVE-2026-59142 create an out-of-bounds read?

This vulnerability falls under the weakness class CWE-125. The code trusts offset and length values stored directly in a memory-mapped file without verifying them. When the software reads these values to perform memory operations, it can be tricked into accessing data beyond the intended buffer, leading to memory disclosure or a process crash.

What triggers this vulnerability in the software?

The issue is triggered when the application performs operations like iterating, draining, or using cursors on the hash map. Simply retrieving a single value via the 'get' path does not trigger this bug, as that specific function correctly validates the offset and length independently.

Do I need to worry if my application is not internet-facing?

According to Halo Surface Signal, this vulnerability is very unlikely to be exploited remotely because it relies on local file access. An attacker must already have the ability to write to the specific backing file used by the shared memory segment to successfully trigger the flaw.

What are the first steps to address this CVE?

Begin by auditing your systems to locate where Data::HashMap::Shared is currently utilized. Once identified, verify if the module version is older than 0.14. Finally, coordinate with your platform team to assess the security of the file permissions governing the backing files used by these processes.

References

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.