Vulnerability

CVE-2026-49955

Medium· 5.3CVSS5.3EPSS0%

.rules3/5

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.

Threat signal

53/100

Elevated

Severity

medium

CVSS

5.3

EPSS

Active

CVSS

v3.1via NVDOpen in FIRST calculator →

5.3/ 10MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Attack VectorNetworkExploitable remotely over the internet — no local access needed.
Attack ComplexityLowNo special conditions — exploit works reliably.
Privileges RequiredNoneUnauthenticated — no credentials needed.
User InteractionNoneFully automated — no victim action needed.
ScopeUnchangedImpact contained to the vulnerable component.
Confidentiality ImpactNoneNo confidentiality impact.
Integrity ImpactNoneNo integrity impact.
Availability ImpactLowReduced performance / interruptions.

EPSS

Exploit prediction · 30-day horizonFIRST.org →

0.15%

probability of exploitation in next 30 days

p35

higher than 35% of all CVEs

3-day trend↑ 0pp

Low exploitation likelihood — defer if no other signals fire.

Vendor VEX

No VEX statements published for CVE-2026-49955. Vendors publish VEX (Vulnerability Exploitability eXchange) to assert per-product whether a CVE is actually exploitable in their distribution.

SSVCDefer

No exploitation, limited impact or prevalence

exploitation: none
automatable: no
impact: partial
mission: support

Lifecycle

2026-06-09Published
2026-06-09Last modified1 source

References

No source-event history recorded yet. New revisions will appear here as ingestors re-fetch this CVE.