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CVE-2026-44660

Ultrajson vulnerability

7.5 HIGHPublic exploitEPSS 0.64%
  1. Published27 May 2026

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.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityNone
IntegrityNone
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

Ultrajson< 5.12.1

Remediation

Fixed in
Ultrajson≥ 5.12.1

References

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Frequently asked

Is CVE-2026-44660 being actively exploited?

CVE-2026-44660 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.64%.

How severe is CVE-2026-44660?

CVE-2026-44660 has a CVSS 3.1 base score of 7.5, rated high. EPSS estimates a 0.64% probability of exploitation.

Which products are affected by CVE-2026-44660?

Affected products include Ultrajson.

How do I fix CVE-2026-44660?

Upgrade affected software to a fixed version, for example Ultrajson 5.12.1 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-44660 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.