# CVE-2026-48503: Information disclosure in libiec61850

> Remote attackers can read stale buffer data via MMS file service flaws in libIEC61850 when the file service is enabled.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 16 Oct 2026
- **Updated:** 16 Oct 2026
- **Also known as:** GHSA-4c8m-jr3r-h8j2

## What is CVE-2026-48503?

CVE-2026-48503 is a high-severity vulnerability in mz-automation libiec61850, published on 16 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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, 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.

Weakness: CWE-252 (Unchecked Return Value), CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor), CWE-191 (Integer Underflow (Wrap or Wraparound))

## Which versions are affected by CVE-2026-48503?


## How do I fix CVE-2026-48503?

No fix has been published for CVE-2026-48503 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-48503 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-48503 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-48503 and fix it if it is affected.

What it is: CVE-2026-48503 is a high-severity vulnerability in mz-automation libiec61850, published on 16 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-48503 exists.

Affected product: mz-automation libiec61850. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-48503/ (Markdown: https://insights.sbomify.com/CVE-2026-48503/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-48503
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-48503
- OSV: https://osv.dev/vulnerability/CVE-2026-48503

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-48503/
Summaries are generated and may contain mistakes; the official description above is the record.