GHSA-hwr4-mq23-wcv5 · Severity: high · Ecosystem: go — mercure has Topic Selector Cache Key Collision
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.
Conclusion & alert: CVE-2026-39972 is rated Low Risk (32.2/100): CVSS High severity, with low exploitation likelihood (EPSS 0.04%). Mandatory action: Monitor for updates and reassess as exploit intelligence or EPSS changes.
Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.
EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).
| # | Date | Old EPSS score | New EPSS score | Delta (New - Old) |
|---|---|---|---|---|
| 1 | 2026-05-22 | 0.08% | 0.04% | -0.05% |
| 2 | 2026-04-10 | — | 0.08% | — |
Full EPSS history (2 records total)
CVSS metrics for this CVE.
| Base score | Version | Severity | Vector | Exploitability | Impact | Score source |
|---|---|---|---|---|---|---|
| 7.1 | 4.0 | HIGH |
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— | — | [email protected] |
GHSA-hwr4-mq23-wcv5 · Severity: high · Ecosystem: go — mercure has Topic Selector Cache Key Collision
| Vendor | Product | Version | Raw CPE |
|---|---|---|---|
| No affected products in dataset. | |||