How severe is CVE-2025-43855?

CVE-2025-43855 has a CVSS 4.0 base score of 8.7, rated high severity.

Is CVE-2025-43855 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (27th percentile), an estimate of the probability of exploitation in the next 30 days.

How do I fix CVE-2025-43855?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2025-43855 have an EU (EUVD) identifier?

Yes. CVE-2025-43855 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-12106.

When was CVE-2025-43855 published?

CVE-2025-43855 was published on 2025-04-24 and last updated on 2026-06-17.

CVE-2025-43855

CVE-2025-43855 is a high-severity vulnerability with a CVSS 4.0 base score of 8.7. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-248.

Key facts

Severity: High (CVSS 4.0 base score 8.7)
EPSS exploit prediction: 0% (27th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2025-12106
Weakness: CWE-248
Published: 2025-04-24
Last modified: 2026-06-17

Description

tRPC allows users to build & consume fully typesafe APIs without schemas or code generation. In versions starting from 11.0.0 to before 11.1.1, an unhandled error is thrown when validating invalid connectionParams which crashes a tRPC WebSocket server. This allows any unauthenticated user to crash a tRPC 11 WebSocket server. Any tRPC 11 server with WebSocket enabled with a createContext method set is vulnerable. This issue has been patched in version 11.1.1.

Frequently asked questions

What is CVE-2025-43855?: tRPC allows users to build & consume fully typesafe APIs without schemas or code generation. In versions starting from 11.0.0 to before 11.1.1, an unhandled error is thrown when validating invalid connectionParams which crashes a tRPC WebSocket server. This allows any unauthenticated user to crash a tRPC 11 WebSocket server. Any tRPC 11 server with WebSocket enabled with a createContext method set is vulnerable. This issue has been patched in version 11.1.1.
How severe is CVE-2025-43855?: CVE-2025-43855 has a CVSS 4.0 base score of 8.7, rated high severity.
Is CVE-2025-43855 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (27th percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2025-43855?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2025-43855 have an EU (EUVD) identifier?: Yes. CVE-2025-43855 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-12106.
When was CVE-2025-43855 published?: CVE-2025-43855 was published on 2025-04-24 and last updated on 2026-06-17.

References

Other CWE-248 vulnerabilities

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