# CVE-2026-59142: Memory corruption in Data::HashMap::Shared

> A local attacker can trigger an out-of-bounds read in the Perl Data::HashMap::Shared library by manipulating the backing file, causing crashes or memory disclosure.

- **Severity:** Critical 9.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 21 Jul 2026
- **Updated:** 22 Jul 2026
- **Also known as:** GHSA-4m33-8fcc-g5rp

## What is CVE-2026-59142?

CVE-2026-59142 is a critical memory corruption vulnerability in EGOR Data::HashMap::Shared, published on 21 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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.

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-59142?


## How do I fix CVE-2026-59142?

No fix has been published for CVE-2026-59142 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-59142 being exploited?

There is no known exploitation of CVE-2026-59142 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-59142 and fix it if it is affected.

What it is: CVE-2026-59142 is a critical memory corruption vulnerability in EGOR Data::HashMap::Shared, published on 21 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-59142 in the wild and no public exploit code.

Affected product: EGOR Data::HashMap::Shared. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-59142/ (Markdown: https://insights.sbomify.com/CVE-2026-59142/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-59142
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-59142
- OSV: https://osv.dev/vulnerability/CVE-2026-59142

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-59142/
Summaries are generated and may contain mistakes; the official description above is the record.