Vulnerability-Lookup

CVE-2026-91973 (GCVE-0-2026-91973)

Vulnerability from cvelistv5 – Published: 2026-09-15 15:18 – Updated: 2026-09-15 15:55

Title

Vikunja before 2.6.0 Authentication Bypass via CalDAV BasicAuth

Summary

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.

Severity

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

7.5 (High)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

SSVC

Exploitation: poc Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-09-15 15:53 UTC

CWE

CWE-307 - Improper Restriction of Excessive Authentication Attempts

Assigner

VulnCheck mitre root

References

2 references

URL	Tags
https://github.com/go-vikunja/vikunja/security/ad…	vendor-advisory
https://www.vulncheck.com/advisories/vikunja-befo…	third-party-advisory

Impacted products

1 product

Vendor	Product	Version	CPE status
go-vikunja	vikunja	Affected: 0 , < 2.6.0 (semver) Unaffected: 2.6.0 (semver) cpe:2.3:a:vikunja:vikunja::::::::

Date Public

2026-08-31 00:00

Credits

JellowBeanz26

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-91973

Vulnerability from fkie_nvd - Published: 2026-09-15 16:17 - Updated: 2026-09-15 16:17

Severity

7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Summary

References

	URL	Tags
	disclosure@vulncheck.com	https://github.com/go-vikunja/vikunja/security/advisories/GHSA-m469-88xx-8rx2
	disclosure@vulncheck.com	https://www.vulncheck.com/advisories/vikunja-before-2.6.0-authentication-bypass-via-caldav-basicauth
	134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/go-vikunja/vikunja/security/advisories/GHSA-m469-88xx-8rx2

Impacted products

	Vendor	Product	Version

JSON

To clipboard

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GHSA-P2VV-WRH8-X466

Vulnerability from github – Published: 2026-09-15 18:32 – Updated: 2026-09-15 18:32

Details

Severity

7.5 (High)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

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

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{
  "affected": [],
  "aliases": [
    "CVE-2026-91973"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-307"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-09-15T16:17:54Z",
    "severity": "HIGH"
  },
  "details": "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\u0027s anti-brute-force controls and compromise password-only accounts.",
  "id": "GHSA-p2vv-wrh8-x466",
  "modified": "2026-09-15T18:32:30Z",
  "published": "2026-09-15T18:32:30Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/go-vikunja/vikunja/security/advisories/GHSA-m469-88xx-8rx2"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-91973"
    },
    {
      "type": "WEB",
      "url": "https://www.vulncheck.com/advisories/vikunja-before-2.6.0-authentication-bypass-via-caldav-basicauth"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "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",
      "type": "CVSS_V4"
    }
  ]
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

Action not permitted

CVE-2026-91973 (GCVE-0-2026-91973)

FKIE_CVE-2026-91973

GHSA-P2VV-WRH8-X466

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Sightings

Nomenclature

Related by attack behaviour