Vulnerability in symfony (DEBIAN-CVE-2026-109449)

Summary

Vulnerability in symfony (DEBIAN-CVE-2026-109449). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to 7.4.21+dfsg-1 or later.

Original description

The description as published by the source.

In Symfony Expression Language versions prior to 5.4.54, 6.4.48, 7.4.21, and 8.1.9, the parser of the ExpressionLanguage component built its node tree with no bound on its depth. An expression made of tens of thousands of nested unary operators, array literals, binary operators or property accesses crashed the PHP process, while the tree was being freed. #[Assert\ExpressionSyntax] passes the validated value to ExpressionLanguage::lint(), so an application validating expressions written by its users could be crashed by a single request, and so could any code parsing untrusted expressions. This issue affects symfony/expression-language through v5.4.53, v6.0.0-BETA1 through v6.4.47, v7.0.0-BETA1 through v7.4.20, and v8.0.0-BETA1 through v8.1.8.

Source: OSV.dev (Open Source Vulnerabilities) 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 DEBIAN-CVE-2026-109449 has been found in symfony.
Risk of unauthorized operations or information disclosure.
What to do: upgrade symfony to 7.4.21+dfsg-1 or later.
If unsure, ask your IT team or search "symfony DEBIAN-CVE-2026-109449" on the vendor's site.

DEBIAN-CVE-2026-109449 (symfony)
Patched: 7.4.21+dfsg-1 — 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 symfony.

📍 Affected scope

Check the vendor advisory for the affected versions of symfony.

🔥 Severity

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

🔧 How to fix

Update to 7.4.21+dfsg-1.

🛡️ 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
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
Apply patch patch
```
Upgrade symfony to 7.4.21+dfsg-1
```
ステージング環境で 7.4.21+dfsg-1 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。

Affected packages

Debian:12 symfony

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Debian:13 symfony

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Debian:14 symfony

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"7.4.21+dfsg-1"}]}]

References

advisory security-tracker.debian.org