Vulnerability in Aio-Libs Multidict
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.
Published .
CVSS v3 metric
CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
- Aio-Libs Multidict — versions >= 6.7.0, < 6.9.1
Weakness classification (CWE)
References
Frequently asked questions
- What is CVE-2026-104874?
- CVE-2026-104874 is a medium-severity vulnerability in Aio-Libs Multidict, classified under Missing Release of Memory after Effective Lifetime. CVSS score: 5.3/10. Published 2026-10-02.
- How severe is CVE-2026-104874?
- Medium severity. CVSS v3 base score is 5.3 out of 10.