CVE-2026-88092 critical CVSS 9.4

Vulnerability in Microsoft.AspNetCore.App.Runtime.linux-arm (CVE-2026-88092)

Summary

Vulnerability in Microsoft.AspNetCore.App.Runtime.linux-arm (CVE-2026-88092). Confidential information can be exposed externally. Mitigation: upgrade to 9.0.21 or later.

Original description

The description as published by the source.

Executive summary

Microsoft is releasing this security advisory to provide information about a vulnerability in Microsoft.AspNetCore.Server.Kestrel.Core. This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability.

An aborted Kestrel HTTP/1 connection can reparse unread request-body bytes as another request, creating a request-smuggling or desynchronization path.

Announcement

Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/472

CVSS Details

Version: 3.1
Severity: Critical
Score: 9.4
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L
Weakness: CWE-444 (Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling'))

Affected Platforms

Platforms: Windows, Linux, macOS
Architectures: All

Affected Packages

The vulnerability affects Microsoft .NET projects that use an affected package version listed below.

Package name	Affected version	Patched version
Microsoft.AspNetCore.App.Runtime.linux-arm	>= 8.0.0, <= 8.0.31	8.0.32
Microsoft.AspNetCore.App.Runtime.linux-arm64	>= 8.0.0, <= 8.0.31	8.0.32
[Microsoft.AspNetCore.App.Runtime.linux-musl-arm](https://www.nuget.org/packages/Microsof…

Source: GitHub Security Advisories (Global) NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-88092 has been found in Microsoft.AspNetCore.App.Runtime.linux-arm.
Confidential information can be exposed externally. CVSS score: 9.4/10.
What to do: upgrade Microsoft.AspNetCore.App.Runtime.linux-arm to 9.0.21 or later.
If unsure, ask your IT team or search "Microsoft.AspNetCore.App.Runtime.linux-arm CVE-2026-88092" on the vendor's site.

CVE-2026-88092 (Microsoft.AspNetCore.App.Runtime.linux-arm) — CWE-444 / CVSS v3 9.4
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Patched: 9.0.21 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (CWE-444) exists in Microsoft.AspNetCore.App.Runtime.linux-arm.

📍 Affected scope

Check the vendor advisory for the affected versions of Microsoft.AspNetCore.App.Runtime.linux-arm.

🔥 Severity

Severity: Critical (CVSS 9.4/10). Confidential information can be exposed externally.

🔧 How to fix

Update to 9.0.21.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'Microsoft.AspNetCore.App.Runtime.linux-arm' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

1
Identify exposure identify
```
grep -r 'Microsoft.AspNetCore.App.Runtime.linux-arm' . | grep -v node_modules
```
リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で Microsoft.AspNetCore.App.Runtime.linux-arm を grep し、稼働しているサービス・バージョンを把握する。
2
Apply patch patch
```
Upgrade Microsoft.AspNetCore.App.Runtime.linux-arm to 9.0.21
```
ステージング環境で 9.0.21 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
3
Post-deployment verification verify
```
Confirm patched version is live in production
```
パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。