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TI-2026-32560 Aliases CVE-2026-44660GHSA-c38f-wx89-p2xg

UltraJSON: Memory Leak in ujson.dump() on Write Failure

Priority HIGH 77CWE-401Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Attack requirements
None
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
Partial Red Hat: 4 fixed, 3 without a fix

Attack profile from CVSS 4.0 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-401.

Summary

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00421 36th percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Partial ultrajson (ultrajson): 5.12.1ujson (PyPI): 5.12.1Red Hat: 6 advisoriesRed Hat: 4 fixed, 3 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
ultrajsonultrajsonbefore 5.12.15.12.1Patch availableCNA
—ujson (PyPI)before 5.12.15.12.1Patch availableGHSA-c38f-wx89-p2xg
  • ultrajson Vendorultrajson Affected before 5.12.1 Fixed in 5.12.1 Patch available CNA
  • ujson (PyPI) Vendor— Affected before 5.12.1 Fixed in 5.12.1 Patch available GHSA-c38f-wx89-p2xg

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:ultrajson_project:ultrajson:*:*:*:*:*:python:*:*before 5.12.1Vulnerableultrajson
  • cpe:2.3:a:ultrajson_project:ultrajson:*:*:*:*:*:python:*:* Versions before 5.12.1 Vulnerable ·ultrajson

Remediation

  • Fix · CNA ultrajson (ultrajson) Fixed in 5.12.1
  • Fix · GHSA-c38f-wx89-p2xg ujson (PyPI) Fixed in 5.12.1 Advisory →

Red Hat 6 advisories

  • RHSA-2026:87410 Released 2026-10-21 · Red Hat rating Critical
    RHOAI 2.25.12 - Red Hat OpenShift AI
    • Red Hat OpenShift AI 2.25 registry.redhat.io/rhoai/odh-built-in-detector-rhel9, registry.redhat.io/rhoai/odh-caikit-nlp-rhel9, registry.redhat.io/rhoai/odh-codeflare-operator-rhel9 +47
  • RHSA-2026:84734 Released 2026-10-19 · Red Hat rating Critical
    RHOAI 3.4.5 - Red Hat OpenShift AI
    • Red Hat OpenShift AI 3.4 registry.redhat.io/rhoai/odh-ai-gateway-payload-processing-rhel9, registry.redhat.io/rhoai/odh-automl-rhel9, registry.redhat.io/rhoai/odh-autorag-rhel9 +47
  • RHSA-2026:60520 Released 2026-08-27 · Red Hat rating Critical
    RHOAI 3.4.4 - Red Hat OpenShift AI
    • Red Hat OpenShift AI 3.4 registry.redhat.io/rhoai/odh-automl-rhel9, registry.redhat.io/rhoai/odh-autorag-rhel9, registry.redhat.io/rhoai/odh-built-in-detector-rhel9 +47
Show 3 more Red Hat advisories
  • RHSA-2026:51347 Released 2026-08-06 · Red Hat rating Moderate
    General availability of the satellite/iop-host-inventory-rhel9 container image
    • Red Hat Satellite 6.18 registry.redhat.io/satellite/iop-host-inventory-rhel9
  • RHSA-2026:51195 Released 2026-08-06 · Red Hat rating Moderate
    General availability of the satellite/iop-host-inventory-rhel9 container image
    • Red Hat Satellite 6.19 registry.redhat.io/satellite/iop-host-inventory-rhel9
  • RHSA-2026:42644 Released 2026-07-21 · Red Hat rating Important
    RHOAI 2.25.9 - Red Hat OpenShift AI
    • Red Hat OpenShift AI 2.25 registry.redhat.io/rhoai/odh-caikit-tgis-serving-rhel9, registry.redhat.io/rhoai/odh-feature-server-rhel9, registry.redhat.io/rhoai/odh-kserve-storage-initializer-rhel9 +36

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

ProductStatusPlan or fix
Exploit IntelligenceAffectedNo fix yet
Red Hat Enterprise Linux AI (RHEL AI) 3AffectedNo fix planned: Will not fix
Red Hat OpenShift AI (RHOAI)AffectedNo fix yet
Red Hat OpenShift AI 2.25Fixed RHSA-2026:42644, RHSA-2026:87410
Red Hat OpenShift AI 3.4Fixed RHSA-2026:60520, RHSA-2026:84734
Red Hat Satellite 6.18Fixed RHSA-2026:51347
Red Hat Satellite 6.19Fixed RHSA-2026:51195
Not affected: 7 products
  • Migration Toolkit for Applications 8
  • Red Hat OpenShift AI (RHOAI)
  • Red Hat OpenShift AI 2.25
  • Red Hat OpenShift AI 3.4
  • Red Hat OpenStack Platform 16.2
  • Red Hat OpenStack Platform 17.1
  • Red Hat OpenStack Platform 18.0

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-44660
  2. 2026-10-03 Alias added: GHSA-c38f-wx89-p2xg
  3. 2026-10-20 Fix available: RHSA-2026:84734 · Red Hat
  4. 2026-10-20 Affected versions changed · Red Hat
  5. 2026-10-21 EPSS moved to the 50th–90th percentile
  6. 2026-10-22 Fix available: RHSA-2026:87410 · Red Hat
  7. 2026-10-23 Affected versions changed · Red Hat
  8. 2026-10-25 EPSS moved to the below the 50th percentile
  9. 2026-11-03 Affected versions changed · Red Hat
  10. 2026-11-06 Fix available: RHSA-2026:42644 · Red Hat

References

Exploit 1

Patch 1

Advisory 1

Other 2

  • TI-2026-25335 UltraJSON has an integer overflow handling large indent leads to buffer overflow or infinite loop CVSS 3.1HIGH 7.5
  • TI-2022-13160 Incorrect handling of invalid surrogate pair characters in ujson CVSS 3.1HIGH 7.5
  • TI-2026-25334 UltraJSON has a Memory Leak parsing large integers allows DoS CVSS 3.1HIGH 7.5
  • TI-2026-39683 UltraJSON: Malformed/Truncated UTF-8 Accepted and Silently Rewritten in ujson.dumps() CVSS 3.1MEDIUM 6.5
  • TI-2022-13161 Double free of buffer during string decoding in ujson CVSS 3.1MEDIUM 5.9
  • TI-2021-20961 UltraJSON (aka ujson) through 5.1.0 has a stack-based buffer overflow in… CVSS 3.1MEDIUM 5.5

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences