Vulnerability in Microsoft System.Security.Cryptography.Xml (CVE-2026-96222)
Summary
Vulnerability in Microsoft System.Security.Cryptography.Xml (CVE-2026-96222). Confidential information can be exposed externally. Exploitable via KeyInfoX509Data. Mitigation: upgrade to 8.0.5 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 System.Security.Cryptography.Xml. This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability.
KeyInfoX509Data can accept serialized certificate formats containing attacker-controlled chain metadata instead of requiring a plain X.509 certificate, contributing to certificate-forgery and token-spoofing paths.
Announcement
Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/474
CVSS Details
- Version: 3.1
- Severity: High
- Score: 7.4
- Vector:
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N - Weakness: CWE-295 (Improper Certificate Validation)
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 |
|---|---|---|
| System.Security.Cryptography.Xml | >= 8.0.0, <= 8.0.4 | 8.0.5 |
Advisory FAQ
How do I know if I am affected?
If using a package listed in affected packages, you're exposed to the vulnerability.
How do I fix the issue?
- To fix the issue please install the latest version of .NET. If you…
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-2026-96222 has been found in Microsoft System.Security.Cryptography.Xml.
Attackers can target a specific entry point like KeyInfoX509Data over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 7.4/10.
What to do: upgrade Microsoft System.Security.Cryptography.Xml to 8.0.5 or later.
If unsure, ask your IT team or search "Microsoft System.Security.Cryptography.Xml CVE-2026-96222" on the vendor's site.
CVE-2026-96222 (Microsoft System.Security.Cryptography.Xml) — CWE-295 / CVSS v3 7.4
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: KeyInfoX509Data
Patched: 8.0.5 — 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.
A vulnerability (CWE-295) exists in Microsoft System.Security.Cryptography.Xml. Attackers reach the vulnerable code path via KeyInfoX509Data without authentication.
Check the vendor advisory for the affected versions of Microsoft System.Security.Cryptography.Xml. Attack surface: KeyInfoX509Data.
Severity: High (CVSS 7.4/10). Confidential information can be exposed externally.
Update to 8.0.5.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'System.Security.Cryptography.Xml' . 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
-
1Identify exposure identify
grep -r 'System.Security.Cryptography.Xml' . | 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
System.Security.Cryptography.Xmlを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade Microsoft System.Security.Cryptography.Xml to 8.0.5ステージング環境で 8.0.5 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。
-
3Post-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
References
- REDHAT Red Hat
- web github.com
- web github.com
- web github.com
- web github.com
- web secure@microsoft.com