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CVE-2026-45063 critical CVSS 9.1

Vulnerability in symfony/security-http (CVE-2026-45063)

Summary

Vulnerability in symfony/security-http (CVE-2026-45063). Confidential information can be exposed externally. Exploitable via X509Authenticator. Mitigation: upgrade to 8.0.12 or later.

Original description

The description as published by the source.

Description

X509Authenticator implements client-certificate (mTLS) authentication: the web server validates the client's certificate against a trusted CA, then passes the certificate's Subject DN (Distinguished Name: a string like CN=Alice,O=Example,emailAddress=alice@example.com) to Symfony via $_SERVER['SSL_CLIENT_S_DN']. Symfony extracts the user identifier from that string.

The extraction uses an unanchored regex that matches emailAddress= anywhere in the DN string: including inside the value of a different RDN (Relative Distinguished Name: one key=value component of the DN), such as CN. An attacker who can obtain a certificate from a trusted CA with a free-text CN can smuggle emailAddress=victim@target inside the CN value and be authenticated as the victim.

Resolution

The X509Authenticator now uses a regex that anchors the match to an RDN boundary (start of string, or following a , / / separator).

The patch for this issue is available here for branch 5.4.

Credits

Symfony would like to thank Claude Mythos Preview (via Project Glasswing) for reporting the issue and providing the fix.

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-2026-45063 has been found in symfony/security-http.
Attackers can target a specific entry point like X509Authenticator over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 9.1/10.
What to do: upgrade symfony/security-http to 8.0.12 or later.
If unsure, ask your IT team or search "symfony/security-http CVE-2026-45063" on the vendor's site.

CVE-2026-45063 (symfony/security-http) — CWE-290 / CVSS v3 9.1
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: X509Authenticator
Patched: 8.0.12 — 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-290) exists in symfony/security-http. Attackers reach the vulnerable code path via X509Authenticator without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of symfony/security-http. Attack surface: X509Authenticator.

🔥 Severity

Severity: Critical (CVSS 9.1/10). Confidential information can be exposed externally.

🔧 How to fix

Update to 8.0.12.

🛡️ 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 'symfony/security-http' . 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 'symfony/security-http' . | 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 symfony/security-http 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 symfony/security-http to 8.0.12

    ステージング環境で 8.0.12 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

composer symfony/security-http
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"8.0.12"}]}]
composer symfony/symfony
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"8.0.12"}]}]
Packagist symfony/security-http
[{"type":"ECOSYSTEM","events":[{"introduced":"8.0.0-BETA1"},{"fixed":"8.0.12"}]}]
Packagist symfony/symfony
[{"type":"ECOSYSTEM","events":[{"introduced":"8.0.0-BETA1"},{"fixed":"8.0.12"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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