What’s Vulnerable › Vulnerabilities

CVE-2026-53522: Nezha Monitoring: Unbounded WebSocket Streams — Resource Exhaustion DoS

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-06-12 · updated 2026-10-25
• Weakness: CWE-770

Description

Nezha Monitoring is a self-hostable, lightweight, servers and websites monitoring and O&M tool. From version 1.0.0 to before version 2.2.0, the Nezha dashboard exposes two endpoints that create long-lived WebSocket streams to monitored agents: POST /api/v1/terminal → createTerminal() (terminal.go:27-67) and POST /api/v1/file → createFM() (fm.go:28-67). Both call rpc.NezhaHandlerSingleton.CreateStream(streamId, ...) which inserts a new ioStreamContext into an unbounded map[string]*ioStreamContext (s.ioStreams in io_stream.go:59-67). There is no per-user rate limit, no global semaphore, and no per-server connection cap. This issue has been patched in version 2.2.0.

Affected products

• nezhahq nezha: from 1.0.0, < 2.2.0

References

• https://github.com/nezhahq/nezha/security/advisories/GHSA-jg62-j5h6-8mpq
• https://github.com/nezhahq/nezha/security/advisories/GHSA-jg62-j5h6-8mpq

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