---
id: CVE-2026-104874
title: Multidict is an implementation of a multidict data structure
summary: >-
  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() - ope…
severity: medium
cvss: 5.3
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L'
cwe:
  - CWE-401
vendor: aio-libs
product: multidict
affected:
  - 'multidict >= 6.7.0, < 6.9.1'
published: '2026-10-02'
updated: '2026-10-02'
sourceUpdated: '2026-10-02T21:16:54.993'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-104874'
references:
  - url: >-
      https://github.com/aio-libs/multidict/commit/350b4a07bf8ff851b6d7544e81b1c748bdc74c40
    label: security-advisories@github.com
  - url: 'https://github.com/aio-libs/multidict/releases/tag/v6.9.1'
    label: security-advisories@github.com
  - url: >-
      https://github.com/aio-libs/multidict/security/advisories/GHSA-54p9-h82j-f925
    label: security-advisories@github.com
tags:
  - nvd
  - cve.org
ingestedAt: '2026-10-02T22:33:09.846Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.