CVE-2026-55091 flat-to-nested - Prototype Pollution

flat-to-nested < 1.1.2 contains a prototype pollution caused by using attacker-controlled id and parent fields as keys in internal objects, letting attackers corrupt application logic or cause denial of service, exploit requires attacker-controlled input to convert().

CVSS base score 7.5 /10
High
CISA KEV
Not listed
Public exploit
None known
Authentication
Not required
EPSS
0.50% chance of exploitation in 30 days
View the NVD record ↗

Details

Type
Prototype Pollution
Impact
Denial Of Service, Data Tampering
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Published
14 September 2026
Updated
15 October 2026
Weakness
CWE-915

Vendor fix

Update to version 1.1.2 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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