What is the CVSS score of CVE-2026-91972?

CVE-2026-91972 has a CVSS 4.0 base score of 8.7 (High). CVSS vector: 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. EPSS exploitation probability: 0.5%.

Is there a public PoC exploit available for CVE-2026-91972?

Yes, a public proof-of-concept exploit is available for CVE-2026-91972. Prioritise patching immediately. EPSS: 0.5%.

Is there a patch available for CVE-2026-91972?

Yes, a patch is available for CVE-2026-91972. Update the affected software to the latest version immediately.

Vikunja CVE-2026-91972

EUVD-2026-78648 HIGH

Improper Restriction of Excessive Authentication Attempts (CWE-307)

2026-09-15 VulnCheck

GHSA-6rvj-qwjf-3m4q

GHSA-m4vj-wr5q-cmvr

Information Disclosure Vikunja Go Vikunja

8.7

CVSS 4.0 · Vendor: VulnCheck

View

Vulnerability Assessment

Weakness

CWE

CWE-307

OWASP Top 10:2025

A07:2025 - Authentication Failures

ASVS 5.0

V6 - Authentication Brute-force prevention, rate limiting

This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).

1 PoC candidate (unverified) Patch available 0.5% exploitation probability (EPSS)

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AnalysisAIv1 – Sep 15, 2026

Vikunja versions before 2.6.0 ship authentication endpoints under /api/v2 (login, register, password-reset, and OAuth token issuance) with no rate limiting, so remote unauthenticated attackers can hammer them with unbounded requests to guess credentials, enumerate accounts, and flood mailboxes with password-reset messages. The exposure is a confidentiality problem — the supplied CVSS 4.0 vector rates high impact to data confidentiality but none to integrity or availability — and a vendor patch exists in 2.6.0. There is no public exploit identified at time of analysis and the flaw is not listed in CISA KEV, so this is best treated as a hardening gap that becomes serious the moment an instance is reachable from untrusted networks.

Affected VersionsENISA

vikunja 0 <2.6.0

Affected Packages

go code.vikunja.io/api fix: 2.6.0

euvd vikunja fix: 2.6.0

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 2 packages in go, euvd

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (VulnCheck) PRIMARY 8.7 HIGH

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

Primary rating from Vendor (VulnCheck) · only source for this CVE.

CVSS VectorVendor: VulnCheck

Attack Vector

Network

Attack Complexity

Low

Attack Requirements

None

Privileges Required

None

User Interaction

None

Vulnerable system: Confidentiality

High

Vulnerable system: Integrity

None

Vulnerable system: Availability

None

Subsequent system: Confidentiality

None

Subsequent system: Integrity

None

Subsequent system: Availability

None

Lifecycle Timeline

Patch available

Sep 15, 2026 - 16:03 EUVD

CVE Published

Sep 15, 2026 - 15:18 cve.org

HIGH 8.7

DescriptionCVE.org

Vikunja versions before 2.6.0 fail to apply rate limiting to /api/v2 public authentication endpoints including login, register, password-reset, and OAuth token routes. Remote unauthenticated attackers can perform unbounded credential guessing, account enumeration, and password-reset flooding attacks without throttling restrictions.

Technical POC Analysis

CWE-307 (Improper Restriction of Excessive Authentication Attempts), in Vikunja's own Go API server (code.vikunja.io/api), specifically the route registration code.

Full technical POC analysis - root cause, step-by-step exploitation and patch breakdown - is part of the Pro and Business plans.

Latest POC

1 PoC candidate from github (unverified)

Threat Intelligence Overview

EPSS Score

0.5%

Top 59% exploitable

Threat Intel

1 source

Data Quality

6 sources

Confidence: High

EUVD

NVD

CVE.org

EPSS GHSA

GitHub

VulDB

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity HIGH

CISA KEV No

Public POC Yes

EPSS 0.5%

Patch available Yes

Active threat No

Deciding rule

HIGH severity (CVSS 7.0-8.9)

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Scheduled

Exploitation· derived

Poc

System Exposure· derived

Open

Automatable· derived

Yes

Human Impact· derived

Medium

Priority Score

Low Medium High Critical

KEV: 0

EPSS: 0

CVSS: +44

PoC: +20

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Attack Technique

Information Disclosure MEDIUM

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.