EUVD-2026-78649Severity by source
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Network-reachable BasicAuth guessing with no auth or interaction needed, so PR:N/UI:N/AC:L; only confidentiality is impacted, giving C:H/I:N/A:N.
Primary rating from Vendor (VulnCheck).
CVSS VectorVendor: VulnCheck
Lifecycle Timeline
3DescriptionCVE.org
Vikunja before 2.6.0 contains an authentication bypass vulnerability in CalDAV BasicAuth endpoints that lack rate limiting protection. Remote unauthenticated attackers can issue unbounded credential-guessing requests against /dav, /.well-known, and /feeds routes to bypass the instance's anti-brute-force controls and compromise password-only accounts.
AnalysisAI
Vikunja instances before 2.6.0 expose CalDAV BasicAuth endpoints (/dav, /.well-known, and /feeds) that are not covered by the application's anti-brute-force controls, letting a remote unauthenticated attacker send an unlimited number of credential-guessing requests. Successful guessing against password-only accounts yields full read access to the victim's tasks, projects, and feeds data. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires a Vikunja deployment below 2.6.0 whose CalDAV/feed endpoints (/dav, /.well-known, /feeds) are reachable by the attacker - typically an instance exposed to the internet or to an untrusted network segment - and at least one account that authenticates with a password guessable from a dictionary or credential list. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 4.0 base vector (AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N) yields 8.7 and reflects unauthenticated, low-complexity, network-reachable exploitation with high confidentiality impact. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Upgrade Vikunja to 2.6.0 or later, which the vendor confirms contains the fix (patch status: available from vendor). … Detailed patch versions, workarounds, and compensating controls in full report. |
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External POC / Exploit Code
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