What’s Vulnerable › Vulnerabilities

CVE-2026-49955: Hermes WebUI < 0.51.270 Resource Exhaustion via passkey/options

• Severity: medium (CVSS 5.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.6% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-06-09 · updated 2026-07-23
• Weakness: CWE-770

Description

Hermes WebUI before version 0.51.270 contains a resource exhaustion vulnerability that allows unauthenticated remote attackers to degrade service availability by repeatedly calling the passkey options endpoint without completing assertion. Attackers can send unlimited POST requests to the authentication endpoint, causing unbounded growth of the challenge store file and excessive CPU and disk I/O through repeated JSON file rewrites.

Affected products

• nesquena hermes-webui: before 0.51.270 — fixed in 0.51.270

How to fix

Upgrade to a fixed version: nesquena hermes-webui 0.51.270. Check the vendor advisory for mitigations.

References

• https://github.com/nesquena/hermes-webui/commit/58528a4d88b0fa4f7b822e31d6051c669769bd3b
• https://github.com/nesquena/hermes-webui/pull/3624
• https://github.com/nesquena/hermes-webui/pull/3674
• https://github.com/nesquena/hermes-webui/releases/tag/v0.51.270
• https://www.vulncheck.com/advisories/hermes-webui-resource-exhaustion-via-passkey-options

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