CVE-2026-104874 (CVSS 5.3)

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.

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CVSS v3.1 Score

5.3

MEDIUM

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

EPSS — Exploit Prediction

0.0030

Probability of exploitation

0.21%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-401 CWE-401

References

Other 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

Frequently Asked Questions

What is 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. It has a CVSS v3.1 base score of 5.3 (MEDIUM).

How severe is CVE-2026-104874? +

CVE-2026-104874 has a CVSS v3.1 score of 5.3 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0030, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-104874? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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