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CVE-2026-44660
ANC
High

UltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Prior to 5.12.1, when ujson.dump() writes to …

CVSS
8.7
High
EPSS
0.00
p29
Published
2026-01-01
Updated
2026-01-01
Description

UltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Prior to 5.12.1, when ujson.dump() writes to a file-like object and the write operation raises an exception, the serialized JSON string object is not decremented, leaking memory. Each failed write operation leaks the full size of the serialized payload. This vulnerability is fixed in 5.12.1.

Tags · CWE
Pre-auth
CWE-401
Affected products
Ultrajson < 5.12.1
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
Timeline
2026-01-01
Published
2026-01-01
Updated
CVSS 3.1 breakdown
Attack Vector
AV: N
Network (N)
Attack Complexity
AC: L
Low (L)
Attack Requirements
AT: N
None
Privileges Required
PR: N
None (N)
User Interaction
UI: N
None (N)
Vulnerable System Confidentiality
VC: N
None (N)
Vulnerable System Integrity
VI: N
None (N)
Vulnerable System Availability
VA: H
High (H)
Subsequent System Confidentiality
SC: N
None (N)
Subsequent System Integrity
SI: N
None (N)
Subsequent System Availability
SA: N
None (N)
Exploit Code Maturity
E: X
Not Defined
Confidentiality Requirement
CR: X
Not Defined
Integrity Requirement
IR: X
Not Defined
Availability Requirement
AR: X
Not Defined
Modified Attack Vector
MAV: X
Not Defined
Modified Attack Complexity
MAC: X
Not Defined
Modified Attack Requirements
MAT: X
Not Defined
Modified Privileges Required
MPR: X
Not Defined
Modified User Interaction
MUI: X
Not Defined
Modified Vulnerable System Confidentiality
MVC: X
Not Defined
Modified Vulnerable System Integrity
MVI: X
Not Defined
Modified Vulnerable System Availability
MVA: X
Not Defined
Modified Subsequent System Confidentiality
MSC: X
Not Defined
Modified Subsequent System Integrity
MSI: X
Not Defined
Modified Subsequent System Availability
MSA: X
Not Defined
s
S: X
X
au
AU: X
X
r
R: X
X
v
V: X
X
re
RE: X
X
u
U: X
X
Exploit indicators
EPSS
0.004 · p29
Known exploited (KEV)
No
Known exploits — Сканер-ВС
No Сканер-ВС checks registered for this vulnerability yet.
Affected products
ProductVendorStatus
Tracked
ujsonTracked
ujsonTracked
ultrajson*Tracked