# CVE-2026-56412: CVE-2026-56412

Status: published. Published: 2026-06-21. Updated: 2026-11-10.

libexpat before 2.8.2 does not consider XML_TOK_DATA_CHARS in doCdataSection and thus lacks handler call depth tracking for various calls from within handlers in cases of a policy violation. Thus, a use-after-free can occur. NOTE: this issue exists because of an incomplete fix for CVE-2026-50219.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- libexpat project / libexpat: ≥ 0; < 2.8.2 (affected, semver). Source: CNA: mitre
- Siemens / SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP

## Severity and prioritization

- CVSS 3.1: 4.9 (medium); CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L; source: CNA: mitre

- CISA KEV: No listing in collected sources

- EPSS: 0.18% as of 2026-11-09; percentile 7.48%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-416

## Exploit evidence

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

## References

- https://github.com/libexpat/libexpat/pull/1278 (CNA: mitre)

- https://cert-portal.siemens.com/productcert/html/ssa-457936.html (ADP: siemens-SADP)

## Provenance

- CNA: mitre: https://www.cve.org/CVERecord?id=CVE-2026-56412; retrieved 2026-11-10; source updated 2026-11-10

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-56412; retrieved 2026-11-10; source updated Not reported

Revision: f5fd56c7f79cb1e4fd367f2fe32c681744bcfa481985305a4b6959215034a887

Canonical: https://y2.dev/cve/CVE-2026-56412

## Agent and API access

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- OpenAPI: https://y2.dev/api/openapi.yaml. Agent access metadata: https://y2.dev/cve/agent.json.

Collected public records only. Check source status for coverage and freshness.