CVE-2026-104874

Name of the Vulnerable Software and Affected Versions Multidict versions 6.7.0 through 6.9.0

Description A reference leak exists in the C extension of the multidict data structure. The issue occurs during the items-view reflected union operation, operand | d.items(), within the multidict itemsview or2 impl function, and the subtraction operation, d.items() - operand, within the multidict itemsview sub1 impl function. These operations fail to release new key-identity and value references for each operand element. If an application performs these operations using sequences influenced by an attacker, it can lead to the leak of two strong references per element. Because garbage collection cannot reclaim these references, repeated operations may result in unbounded process memory growth, leading to a denial of service. Pure-Python builds, forward union, intersection, and non-tuple operand elements are not affected.

Recommendations Update to version 6.9.1.