How severe is CVE-2026-28787?

CVE-2026-28787 has a CVSS 3.x base score of 8.2, rated high severity. It is exploitable over network with high attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.

Is CVE-2026-28787 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (19th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-28787?

CVE-2026-28787 affects Hackerbay Oneuptime. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-28787?

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-2026-28787 have an EU (EUVD) identifier?

Yes. CVE-2026-28787 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-9996.

When was CVE-2026-28787 published?

CVE-2026-28787 was published on 2026-03-06 and last updated on 2026-06-17.

CVE-2026-28787

CVE-2026-28787 is a high-severity vulnerability in Hackerbay Oneuptime with a CVSS 3.x base score of 8.2. 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-287.

Key facts

Severity: High (CVSS 3.x base score 8.2)
EPSS exploit prediction: 0% (19th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-9996
Weakness: CWE-287
Affected product: Hackerbay Oneuptime
Published: 2026-03-06
Last modified: 2026-06-17

Description

OneUptime is a solution for monitoring and managing online services. In version 10.0.11 and prior, the WebAuthn authentication implementation does not store the challenge on the server side. Instead, the challenge is returned to the client and accepted back from the client request body during verification. This violates the WebAuthn specification (W3C Web Authentication Level 2, §13.4.3) and allows an attacker who has obtained a valid WebAuthn assertion (e.g., via XSS, MitM, or log exposure) to replay it indefinitely, completely bypassing the second-factor authentication. No known patches are available.

Frequently asked questions

What is CVE-2026-28787?: OneUptime is a solution for monitoring and managing online services. In version 10.0.11 and prior, the WebAuthn authentication implementation does not store the challenge on the server side. Instead, the challenge is returned to the client and accepted back from the client request body during verification. This violates the WebAuthn specification (W3C Web Authentication Level 2, §13.4.3) and allows an attacker who has obtained a valid WebAuthn assertion (e.g., via XSS, MitM, or log exposure) to replay it indefinitely, completely bypassing the second-factor authentication. No known patches are available.
How severe is CVE-2026-28787?: CVE-2026-28787 has a CVSS 3.x base score of 8.2, rated high severity. It is exploitable over network with high attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.
Is CVE-2026-28787 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (19th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-28787?: CVE-2026-28787 affects Hackerbay Oneuptime. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-28787?: 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-2026-28787 have an EU (EUVD) identifier?: Yes. CVE-2026-28787 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-9996.
When was CVE-2026-28787 published?: CVE-2026-28787 was published on 2026-03-06 and last updated on 2026-06-17.

References

https://github.com/OneUptime/oneuptime/security/advisories/GHSA-gjjc-pcwp-c74m

Affected products (1)

cpe:2.3:a:hackerbay:oneuptime:*:*:*:*:*:*:*:*

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