CVE-2026-48503: libIEC61850: Remote information disclosure in MMS file service via out-of-range initialPosition in fileOpen followed by fileRead
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/isomms/server/mmsfileservice.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 FileSystemreadFile 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.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
libIEC61850to a version that resolves this vulnerability.Fixed in 1.6.2
Event History
Frequently Asked Questions
Which deployments are exposed?
libIEC61850 versions before 1.6.2 are exposed when the MMS file service is enabled and reachable by a remote client.
Does an attacker need credentials or user interaction?
No. The issue can be triggered by an unauthenticated remote client, with no user interaction required.
What can be done before upgrading?
Upgrade to version 1.6.2. If upgrading is not immediately possible, disabling the MMS file service prevents the affected fileOpen and fileRead path from being available.