CVE-2026-104874

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.

CVSS 3.1

5.3CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

EPSS

0.4% chance of exploitation in the next 30 days; higher than 38% of CVEs (scores of 2026-10-25)

CWE

CWE-401

Published

2026-10-02

Modified

2026-10-06

Record from

the NVD, synced 2026-10-19

Packages (OSV)

References

• https://github.com/aio-libs/multidict/commit/350b4a07bf8ff851b6d7544e81b1c748bdc74c40
• https://github.com/aio-libs/multidict/releases/tag/v6.9.1
• https://github.com/aio-libs/multidict/security/advisories/GHSA-54p9-h82j-f925
• https://github.com/aio-libs/multidict/security/advisories/GHSA-54p9-h82j-f925

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