CVE-2026-109449
Symfony: Unbounded Nesting in the Expression Parser Lets Untrusted Expressions Crash the Process
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
8.7
Symfony: Unbounded Nesting in the Expression Parser Lets Untrusted Expressions Crash the Process
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.
- Record
CVE-2026-109449- CVSS 4.0
- 8.7 High
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 - Weakness
- CWE-674
- Updated
- 2026-11-02
EUVDEUVD-2026-102134
8.7
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.
- Record
EUVD-2026-102134- CVSS 4.0
- 8.7 High
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 - Updated
- 2026-11-02
NVD
8.7
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.
- Record
CVE-2026-109449- CVSS 4.0
- 8.7 High
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - Weakness
- CWE-674
- Updated
- 2026-11-02
OSV
8.7
Symfony: Unbounded Nesting in the Expression Parser Lets Untrusted Expressions Crash the Process
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.
- Record
CVE-2026-109449- CVSS 4.0
- 8.7 High
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 - Weakness
- CWE-674
- Updated
- 2026-11-02
OSVDEBIAN-CVE-2026-109449
8.7
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.
- Record
DEBIAN-CVE-2026-109449- CVSS 4.0
- 8.7 High
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - Updated
- 2026-11-04
OSVUBUNTU-CVE-2026-109449
8.7
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.
- Record
UBUNTU-CVE-2026-109449- CVSS 4.0
- 8.7 High
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 - Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
symfonyDebian:12 |
All versions, plus listed versions 5.4.23+dfsg-15.4.23+dfsg-1+deb12u15.4.23+dfsg-1+deb12u25.4.23+dfsg-1+deb12u35.4.23+dfsg-1+deb12u4 Show 45 moreShow less5.4.23+dfsg-1+deb12u55.4.24+dfsg-15.4.25+dfsg-15.4.27+dfsg-15.4.28+dfsg-15.4.29+dfsg-15.4.30+dfsg-15.4.31+dfsg-15.4.31+dfsg-25.4.32+dfsg-15.4.33+dfsg-15.4.34+dfsg-15.4.34+dfsg-25.4.35+dfsg-15.4.35+dfsg-25.4.35+dfsg-35.4.52+dfsg-0+deb12u15.4.53+dfsg-0+deb12u16.3.0+dfsg-16.3.0~rc1+dfsg-16.3.0~rc2+dfsg-16.3.1+dfsg-16.3.3+dfsg-16.3.4+dfsg-16.3.5+dfsg-16.3.6+dfsg-16.3.7+dfsg-16.4.0+dfsg-16.4.0~beta2+dfsg-16.4.0~beta3+dfsg-16.4.0~rc1+dfsg-16.4.0~rc2+dfsg-16.4.1+dfsg-16.4.10+dfsg-16.4.11+dfsg-16.4.12+dfsg-16.4.13+dfsg-16.4.14+dfsg-16.4.15+dfsg-16.4.16+dfsg-16.4.16+dfsg-26.4.17+dfsg-16.4.17+dfsg-26.4.17+dfsg-36.4.17+dfsg-4 |
None known |
symfonyDebian:13 |
before 6.4.49+dfsg-0+deb13u1, plus listed versions 6.4.21+dfsg-26.4.21+dfsg-2+deb13u16.4.24+dfsg-16.4.25+dfsg-16.4.40+dfsg-0+deb13u16.4.41+dfsg-0+deb13u1 |
6.4.49+dfsg-0+deb13u1 |
symfonyDebian:14 |
before 7.4.21+dfsg-1, plus listed versions 6.4.21+dfsg-26.4.24+dfsg-16.4.25+dfsg-17.0.4+dfsg-17.0.5+dfsg-1 Show 45 moreShow less7.0.6+dfsg-17.0.7+dfsg-17.1.0~beta1+dfsg-17.1.0~rc1+dfsg-17.1.2+dfsg-17.1.3+dfsg-17.1.4+dfsg-17.1.5+dfsg-17.2.0~beta1+dfsg-17.2.0~beta2+dfsg-17.2.0~rc1+dfsg-17.2.1+dfsg-17.2.2+dfsg-17.2.3+dfsg-17.2.4+dfsg-17.2.5+dfsg-17.2.6-17.3.0+dfsg-17.3.0~beta1+dfsg-17.3.0~beta2+dfsg-17.3.0~rc1+dfsg-17.3.1+dfsg-17.3.2+dfsg-17.3.3+dfsg-17.3.4+dfsg-17.3.5-17.4.0+dfsg-17.4.0+dfsg-27.4.0~beta1-17.4.0~beta1-27.4.0~beta2+dfsg-17.4.0~beta2+dfsg-27.4.0~beta2+dfsg-37.4.0~rc1+dfsg-17.4.0~rc2+dfsg-17.4.0~rc3+dfsg-17.4.10+dfsg-17.4.12+dfsg-17.4.13+dfsg-17.4.13+dfsg-27.4.14+dfsg-17.4.15+dfsg-17.4.15+dfsg-27.4.16+dfsg-17.4.17+dfsg-1 |
7.4.21+dfsg-1 |
symfonyUbuntu:16.04:LTS |
All versions, plus listed versions 2.7.1+dfsg-12.7.5+dfsg-12.7.9+dfsg-12.7.9+dfsg-1ubuntu22.7.10-0ubuntu2 |
None known |
symfonyUbuntu:Pro:18.04:LTS |
All versions, plus listed versions 2.8.7+dfsg-1.3ubuntu13.4.3+dfsg-1ubuntu43.4.6+dfsg-13.4.6+dfsg-1ubuntu0.13.4.6+dfsg-1ubuntu0.1+esm13.4.6+dfsg-1ubuntu0.1+esm2 |
None known |
symfonyUbuntu:Pro:20.04:LTS |
All versions, plus listed versions 4.3.4+dfsg-1ubuntu14.3.8+dfsg-1ubuntu14.3.8+dfsg-1ubuntu1+esm14.3.8+dfsg-1ubuntu1+esm2 |
None known |
symfonyUbuntu:Pro:22.04:LTS |
All versions, plus listed versions 5.2.6+dfsg-1ubuntu75.4.4+dfsg-1ubuntu85.4.4+dfsg-1ubuntu8+esm1 |
None known |
symfonyUbuntu:Pro:24.04:LTS |
All versions, plus listed versions 5.4.23+dfsg-1ubuntu15.4.35+dfsg-3ubuntu16.4.5+dfsg-3ubuntu26.4.5+dfsg-3ubuntu36.4.5+dfsg-3ubuntu3+esm1 |
None known |
symfonyUbuntu:26.10 |
All versions, plus listed versions 7.4.7+dfsg-1ubuntu17.4.9+dfsg-1ubuntu17.4.13+dfsg-2ubuntu17.4.14+dfsg-1ubuntu27.4.15+dfsg-2ubuntu27.4.16+dfsg-1ubuntu2 |
None known |
symfonyUbuntu:26.04:LTS |
All versions, plus listed versions 6.4.24+dfsg-17.4.5+dfsg-1ubuntu17.4.6+dfsg-2ubuntu17.4.7+dfsg-1ubuntu1 |
None known |
History
| Recorded | Changed | Sources |
|---|---|---|
| affected, facts | OSV | |
| first indexed | CVE List, EUVD, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-109449 is a high vulnerability (CVSS 8.7) in Sensiolabs Symfony, published October 15, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.38%, the 31st percentile. Fixed in symfony 6.4.49+dfsg-0+deb13u1.
References
github.com/symfony/symfony/security/advisories/GHSA-7rpj-w9pf-39rr
symfony.com/blog/cve-2026-109449-unbounded-nesting-in-the-expression-parser-lets-untrusted-expressions-crash-the-process
github.com/symfony/symfony/pull/65690
github.com/symfony/symfony/pull/66720
github.com/symfony/symfony/pull/66723
packagist.org/packages/symfony/expression-language
Left out here: 130 versions. The JSON record has them.