# CVE-2026-56405 — libexpat

> As of 2026-06-22, CVE-2026-56405 is a MEDIUM-severity vulnerability in libexpat, CVSS v3.1 6.9. No Threadlinqs-tracked threat campaign has been attributed to CVE-2026-56405 as of 2026-06-22; the identifier is re-checked against the Threadlinqs threat corpus on every daily ingest.

**Last updated:** 2026-06-22

## What is CVE-2026-56405?

libexpat before 2.8.2 has an integer overflow in getAttributeId.

The record classifies CVE-2026-56405 under weakness class [CWE-190](https://intel.threadlinqs.com/cwe/CWE-190). Its CVSS v3 base vector states that the flaw requires local access to the host, needs no prior authentication, needs no user interaction, and has high impact on confidentiality, integrity. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 106 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 6.9 — MEDIUM (`CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L`)
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 3.5/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-06-21, last modified 2026-06-22

## Is CVE-2026-56405 being exploited?

It currently carries a trending score of 30 in the Threadlinqs vulnerability feed.

## Affected products and versions

- [libexpat project](https://intel.threadlinqs.com/vendors/libexpat-project): libexpat

## How to fix CVE-2026-56405

No vendor patch reference has been recorded for CVE-2026-56405 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2026-56405

No threat campaign in the Threadlinqs corpus currently references CVE-2026-56405, in its CVE list or as an indicator. The linkage is recomputed from the live corpus on every daily ingest, so this section fills in as soon as a tracked campaign cites the identifier.

## Sources

Enriched from CVE.org, GitHub Security Advisories. Last verified by Threadlinqs on 2026-06-22.

**Other references**

- [github.com](https://github.com/libexpat/libexpat/pull/1251)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-56405
Full detection coverage and IOCs for threats exploiting CVE-2026-56405 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp