---
id: CVE-2026-48503
title: >-
  libIEC61850 is an open-source implementation of IEC 61850 client and server
  protocols including MMS, GOOSE, Sampled Values, and R-Session
summary: >-
  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,
  the MMS file service in src/mms/iso_mms/server/mms_file_service.c accepts an
  out-o…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N'
cwe:
  - CWE-191
  - CWE-200
  - CWE-252
vendor: mz-automation
product: libiec61850
affected:
  - libiec61850 < 1.6.2
published: '2026-10-16'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T20:04:29.760'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-48503'
references:
  - url: >-
      https://github.com/mz-automation/libiec61850/commit/bba5bf2fab6d7ac88f5accb4c9e90b123436ebf2
    label: security-advisories@github.com
  - url: 'https://github.com/mz-automation/libiec61850/releases/tag/v1.6.2'
    label: security-advisories@github.com
  - url: >-
      https://github.com/mz-automation/libiec61850/security/advisories/GHSA-4c8m-jr3r-h8j2
    label: security-advisories@github.com
  - url: >-
      https://github.com/mz-automation/libiec61850/security/advisories/GHSA-4c8m-jr3r-h8j2
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
tags:
  - nvd
  - cve.org
  - exploit-available
epss: 0.00458
epssPercentile: 0.3951
exploitAvailable: true
ssvc:
  exploitation: poc
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-10-16T16:50:20.616443Z'
ingestedAt: '2026-10-16T17:24:46.894Z'
---

## Overview

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, the MMS file service in src/mms/iso_mms/server/mms_file_service.c accepts an out-of-range initialPosition in fileOpen and stores it in the file-read state. The fileRead path then subtracts the larger read position from the file size using unsigned arithmetic and fails to limit the response to the actual FileSystem_readFile return value. The oversized response can include stale bytes from the reused connection buffer after the requested file contents, disclosing prior response data and protocol fragments to an unauthenticated remote client when the file service is enabled. This issue is fixed in version 1.6.2.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.