Multidict is an implementation of a multidict data structure. From 6.7.0 until 6.9.1, the C extension's items-view reflected union operation, operand | d.items(), in multidict_itemsview_or2_impl and subtraction operation, d.items() - operand, in multidict_itemsview_sub1_impl fail to release new key-identity and value references returned for each operand element. Applications that perform these operations over attacker-influenced sequences can leak two strong references per element, and garbage collection cannot reclaim them, so repeated operations can cause unbounded process memory growth and denial of service. Forward union, intersection, non-tuple operand elements, and pure-Python builds are not affected by this reference leak. This issue is fixed in version 6.9.1.
Advisories

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Fixes

Solution

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Workaround

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History

Sat, 03 Oct 2026 00:30:00 +0000

Type Values Removed Values Added
Weaknesses CWE-911
References
Metrics threat_severity

None

threat_severity

Moderate


Fri, 02 Oct 2026 20:30:00 +0000

Type Values Removed Values Added
Description Multidict is an implementation of a multidict data structure. From 6.7.0 until 6.9.1, the C extension's items-view reflected union operation, operand | d.items(), in multidict_itemsview_or2_impl and subtraction operation, d.items() - operand, in multidict_itemsview_sub1_impl fail to release new key-identity and value references returned for each operand element. Applications that perform these operations over attacker-influenced sequences can leak two strong references per element, and garbage collection cannot reclaim them, so repeated operations can cause unbounded process memory growth and denial of service. Forward union, intersection, non-tuple operand elements, and pure-Python builds are not affected by this reference leak. This issue is fixed in version 6.9.1.
Title Multidict: Reference leak in CIMultiDict/MultiDict items-view union and subtraction
Weaknesses CWE-401
References
Metrics cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-10-02T20:21:50.903Z

Reserved: 2026-10-02T14:59:11.775Z

Link: CVE-2026-104874

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-10-02T21:16:54.993

Modified: 2026-10-02T21:16:54.993

Link: CVE-2026-104874

cve-icon Redhat

Severity : Moderate

Publid Date: 2026-10-02T20:21:50Z

Links: CVE-2026-104874 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-10-03T01:30:18Z

Weaknesses