Vulnerability · Published Oct 15, 2026 · Assigned by Checkmarx
CVE-2026-109449Symfony: Unbounded Nesting in the Expression Parser Lets Untrusted Expressions Crash the Process
High 8.7
In plain English
A high-severity security flaw in symfony from sensiolabs. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 32% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | symfony | no fix listed | DEBIAN-CVE-2026-109449 |
| Debian:13 | symfony | 6.4.49+dfsg-0+deb13u1 | DEBIAN-CVE-2026-109449 |
| Debian:14 | symfony | 7.4.21+dfsg-1 | DEBIAN-CVE-2026-109449 |
| Ubuntu:26.04:LTS | symfony | no fix listed | UBUNTU-CVE-2026-109449 |
| Ubuntu:26.10 | symfony | no fix listed | UBUNTU-CVE-2026-109449 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| sensiolabs | symfony | 0 – before v5.4.54v6.0.0-BETA1 – before v6.4.48v7.0.0-BETA1 – before v7.4.21v8.0.0-BETA1 – before v8.1.9 |
Weakness: CWE-674 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
References
- https://github.com/symfony/symfony/security/advisories/GHSA-7rpj-w9pf-39rr third-party-advisory
- https://symfony.com/blog/cve-2026-109449-unbounded-nesting-in-the-expression-parser-lets-untrusted-expressions-crash-the-process vendor-advisory
- https://github.com/symfony/symfony/pull/65690 patch
- https://github.com/symfony/symfony/pull/66720 patch
- https://github.com/symfony/symfony/pull/66723 patch