# CVE-2026-124540: JSON::XS versions before 4.05 for Perl allow stack exhaustion via nested tagged values under allow_tags in decode_tag

Status: published. Published: 2026-11-14. Updated: 2026-11-14.

JSON::XS versions before 4.05 for Perl allow stack exhaustion via nested tagged values under allow_tags in decode_tag.

With allow_tags, "(" starts a tagged value. Its tag and value are decoded recursively, and each can start another tagged value. Unlike arrays and objects, this nesting is not counted against max_depth.

A run of "(" bytes exhausts the C stack and triggers an uncatchable segmentation fault regardless of max_depth.

## Remediation

- fix: Upgrade to JSON-XS 4.05 or later. (source: CNA: CPANSec)

## Affected products and versions

-  /  (JSON-XS): ≥ 0; < 4.05 (affected, custom). Source: CNA: CPANSec

## Severity and prioritization

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-674

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://metacpan.org/release/MLEHMANN/JSON-XS-4.05/changes (CNA: CPANSec; release-notes)

## Provenance

- CNA: CPANSec: https://www.cve.org/CVERecord?id=CVE-2026-124540; retrieved 2026-11-14; source updated 2026-11-14

Revision: 378e49695c6dbecf06cb1af568f7d03ed6ad4be02693ee4834a16418366c889a

Canonical: https://y2.dev/cve/CVE-2026-124540

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