CVE-2026-109449 Symfony Expression Language - Denial of Service

Symfony Expression Language < 5.4.54, < 6.4.48, < 7.4.21, and < 8.1.9 contains a denial of service caused by unbounded expression tree depth in the parser, letting attackers crash the PHP process by submitting deeply nested expressions, exploit requires sending crafted expressions.

CVSS base score 8.7 /10
High
CISA KEV
Not listed
Public exploit
None known
Authentication
Not required
View the NVD record ↗

Details

Type
Denial Of Service
Impact
Denial Of Service
CVSS 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/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
Published
15 October 2026
Updated
16 October 2026
Weakness
CWE-674

Vendor fix

Update to versions 5.4.54, 6.4.48, 7.4.21, 8.1.9 or later.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

References

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