Mercure has a Topic Selector Cache Key Collision_CVE-2026-39972

7.1 / 10

HIGH

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:L/SC:N/SI:N/SA:N

Description

Mercure is a protocol for pushing data updates to web browsers and other HTTP clients in a battery-efficient way. Prior to 0.22.0, a cache key collision vulnerability in TopicSelectorStore allows an attacker to poison the match result cache, potentially causing private updates to be delivered to unauthorized subscribers or blocking delivery to authorized ones. The cache key was constructed by concatenating the topic selector and topic with an underscore separator. Because both topic selectors and topics can contain underscores, two distinct pairs can produce the same key. An attacker who can subscribe to the hub or publish updates with crafted topic names can exploit this to bypass authorization checks on private updates. This vulnerability is fixed in 0.22.0.

Basic Information

ID CVE-2026-39972

Source GitHub_M

Published Apr 9, 2026 at 16:42

Modified Apr 9, 2026 at 18:59

Affected Product

Vendor dunglas

Product mercure

Version < 0.22.0

Affected Versions dunglas mercure < 0.22.0

CWE Classification

CWE-1289

References

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    "published": "2026-04-09T16:42:22.903Z",
    "modified": "2026-04-09T18:59:49.306Z",
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