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CVE-2021-34532 medium CVSS 5.5

Vulnerability in Microsoft.AspNetCore.Authentication.JwtBearer (CVE-2021-34532)

Summary

Vulnerability in Microsoft.AspNetCore.Authentication.JwtBearer (CVE-2021-34532). Confidential information can be exposed externally. Exploitable via csproj. Mitigation: upgrade to 5.0.9 or later.

Original description

The description as published by the source.

ASP.NET Core and Visual Studio Information Disclosure Vulnerability

Source: NIST National Vulnerability Database 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-2021-34532 has been found in Microsoft.AspNetCore.Authentication.JwtBearer.
Attackers can target a specific entry point like csproj over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 5.5/10.
What to do: upgrade Microsoft.AspNetCore.Authentication.JwtBearer to 5.0.9 or later.
If unsure, ask your IT team or search "Microsoft.AspNetCore.Authentication.JwtBearer CVE-2021-34532" on the vendor's site.

CVE-2021-34532 (Microsoft.AspNetCore.Authentication.JwtBearer) — CVSS v3 5.5
Attack vector: local / no user interaction
Attack surface: csproj / Contoso.Utility / Contoso.Internals
Patched: 5.0.9 — 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 (unclassified) exists in Microsoft.AspNetCore.Authentication.JwtBearer. Attackers reach the vulnerable code path via csproj.

📍 Affected scope

Check the vendor advisory for the affected versions of Microsoft.AspNetCore.Authentication.JwtBearer. Attack surface: csproj / Contoso.Utility / Contoso.Internals.

🔥 Severity

Severity: Medium (CVSS 5.5/10). Confidential information can be exposed externally.

🔧 How to fix

Update to 5.0.9.

🛡️ 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.Authentication.JwtBearer' . 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. 1
    Identify exposure identify 
    grep -r 'Microsoft.AspNetCore.Authentication.JwtBearer' . | 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.Authentication.JwtBearer を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Apply patch patch 
    Upgrade Microsoft.AspNetCore.Authentication.JwtBearer to 5.0.9

    ステージング環境で 5.0.9 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. 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。

Affected packages

nuget Microsoft.AspNetCore.Authentication.JwtBearer
[{"type":"ECOSYSTEM","events":[{"introduced":"5.0.0"},{"fixed":"5.0.9"}]}]
Bitnami aspnet-core
[{"type":"SEMVER","events":[{"introduced":"2.1.0"},{"fixed":"2.1.3"},{"introduced":"3.1.0"},{"fixed":"3.1.18"},{"introduced":"5.0.0"},{"fixed":"5.0.9"}]}]

References

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