aio-libs multidict up to 6.9.0 C extension resource consumption

Summaryinfo

A vulnerability, which was classified as problematic, has been found in aio-libs multidict up to 6.9.0. Affected is the function multidict_itemsview_or2_impl/multidict_itemsview_sub1_impl of the component C extension. The manipulation leads to resource consumption. This vulnerability is referenced as CVE-2026-104874. Remote exploitation of the attack is possible. No exploit is available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in aio-libs multidict up to 6.9.0. It has been rated as problematic. This issue affects the function multidict_itemsview_or2_impl/multidict_itemsview_sub1_impl of the component C extension. The manipulation with an unknown input leads to a resource consumption vulnerability. Using CWE to declare the problem leads to CWE-400. The product does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources. Impacted is availability. The summary by CVE is:

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.

The advisory is shared at github.com. The identification of this vulnerability is CVE-2026-104874 since 10/02/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details are known, but no exploit is available. MITRE ATT&CK project uses the attack technique T1499 for this issue.

Upgrading to version 6.9.1 eliminates this vulnerability.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Vendor

• aio-libs

Name

• multidict

Version

• 6.0
• 6.1
• 6.2
• 6.3
• 6.4
• 6.5
• 6.6
• 6.7
• 6.8
• 6.9.0

Website

• Product: https://github.com/aio-libs/multidict/

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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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