---
id: "CVE-2026-114148"
kind: "vulnerability"
aliases: ["CVE-2026-114148"]
title: "ASP.NET Core: default file permissions let a local user gain higher privileges"
severity: "high"
cvss: 7.8
epss: null
exploited: false
status: "open"
category: "runtime"
products: [{"name": "ASP.NET Core 8 Linux tarballs", "fixed": ["8.0.33"], "affected": ">= 8.0.0, < 8.0.33", "ecosystem": "vendor"}, {"name": "ASP.NET Core 9 Linux tarballs", "fixed": ["9.0.22"], "affected": ">= 9.0.0, < 9.0.22", "ecosystem": "vendor"}]
ecosystems: []
tags: ["aspnet-core", "container", "dotnet", "linux", "runtime", "tarball", "windows"]
not_affected_if: ["extracted-with-no-same-owner", "managed-hosting", "no-local-untrusted-users"]
published_at: "2026-10-29T16:17:58+00:00"
first_seen_at: "2026-10-29T16:25:56+00:00"
updated_at: "2026-10-29T16:39:26+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-114148", "first_seen_at": "2026-10-29T16:25:56+00:00"}, {"source": "analyst", "url": null, "first_seen_at": "2026-10-29T16:39:26+00:00"}]
---

# ASP.NET Core: default file permissions let a local user gain higher privileges

Linux ASP.NET Core runtime and targeting-pack tarballs (and source-built .NET tarballs) carry unsafe numeric file ownership. If they are extracted so that ownership is preserved (for example as root, or in a container image import), a local user can modify runtime files that a more privileged app then uses, and gain higher privileges. It is a local attack only.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- vendor:ASP.NET Core 8 Linux tarballs affected >= 8.0.0, < 8.0.33 fixed 8.0.33
- vendor:ASP.NET Core 9 Linux tarballs affected >= 9.0.0, < 9.0.22 fixed 9.0.22

## How to check

A .NET version number alone does not tell you. Check whether the runtime or targeting pack was installed from an aspnetcore-runtime-*, aspnetcore-runtime-composite-* or aspnetcore-targeting-pack-* Linux tar.gz older than 8.0.33 / 9.0.22 (or from a source-built .NET archive in the affected ranges). Then check that extraction preserved numeric ownership: inspect the install directory (e.g. ls -lnR on it) for files owned by a non-admin UID or writable via group, others or ACLs. Restoring NuGet runtime packages does not introduce the defect.

## Fix

Replace the installation with a clean one in a NEW empty directory from the patched tarball: ASP.NET Core 8.0.33 or 9.0.22 (source-built: 8.0.133, 9.0.123, 10.0.114-servicing.26522.126, 10.0.403-servicing.26523.112, 11.0.100-rc.3.26522.148). Extract with tar --no-same-owner --no-same-permissions in an admin-controlled directory. Updating over the old tree or changing a NuGet reference does not fix it. Rebuild custom container images the same way.

## Timeline

- 2026-10-29T16:25:56+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-114148
- 2026-10-29T16:39:26+00:00 analyst — Read Microsoft advisory GHSA-r6pf-x897-gm86 (Oct 25 2026 OOB). Bug is Linux tarball file ownership (CWE-276), not ASP.NET Core code; fix is clean reinstall from patched tarball. No exploitation or PoC seen; no social search done (B tier, local EoP).

## Documents

- [advisory] Microsoft Security Advisory CVE-2026-114148 (GHSA-r6pf-x897-gm86) https://github.com/dotnet/aspnetcore/security/advisories/GHSA-r6pf-x897-gm86
- [fix] .NET October 2026 Out-of-Band Security Updates https://devblogs.microsoft.com/dotnet/dotnet-october-2026-oob-security-updates/

## From the sources

Incorrect default permissions in ASP.NET Core allows an authorized attacker to elevate privileges locally.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_