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CVE-2020-5255

Vulnerability in Symfony (CVE-2020-5255)

Summary

Vulnerability in Symfony (CVE-2020-5255). Risk of unauthorized operations or information disclosure. Exploitable via Response.

Original description

The description as published by the source.

Description

When a Response does not contain a Content-Type header, Symfony falls back to the format defined in the Accept header of the request, leading to a possible mismatch between the response's content and Content-Type header. When the response is cached, this can lead to a corrupted cache where the cached format is not the right one.

Resolution

Symfony does not use the Accept header anymore to guess the Content-Type.

The patch for this issue is available here for the 4.4 branch.

Credits

I would like to thank Xavier Lacot from JoliCode for reporting & Yonel Ceruto and Tobias Schultze for fixing the issue.

Source: OSV.dev (Open Source Vulnerabilities) NVD GitHub Advisory OSV

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-2020-5255 has been found in Symfony.
Attackers can target a specific entry point like Response over the network to misuse the product.
Risk of unauthorized operations or information disclosure.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Symfony CVE-2020-5255" on the vendor's site.

CVE-2020-5255 (Symfony)
Attack vector: remote (network-reachable) / no user interaction
Attack surface: Response / Accept
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 Symfony. Attackers reach the vulnerable code path via Response.

📍 Affected scope

Check the vendor advisory for the affected versions of Symfony. Attack surface: Response / Accept.

🔥 Severity

Severity: ?. Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to the patched release per vendor advisory.

🛡️ 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' . 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' . | 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 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
    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

Packagist symfony/http-foundation
[{"type":"ECOSYSTEM","events":[{"introduced":"5.0.0"},{"fixed":"5.0.7"}]}]
Packagist symfony/symfony
[{"type":"ECOSYSTEM","events":[{"introduced":"5.0.0"},{"fixed":"5.0.7"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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