Security readout for executives and security teams
Plain-English summary
Vikunja versions before 2.2.1 reportedly allow attackers to expose link-share hashes and then access attachments across projects. The impact is broad: confidential files may be downloaded or deleted across the instance. The bundle reports critical severity, but does not cite confirmed active exploitation.
Executive priority
Treat as urgent for any Vikunja instance storing business files. The vulnerability can affect confidentiality, integrity, and availability of attachments across projects, so prioritize upgrade and exposure review ahead of routine maintenance.
Technical view
The issue combines share-hash disclosure in LinkSharing.ReadAll with a cross-project attachment IDOR in GetTaskAttachment. Authorization checks use a caller-supplied task ID, while attachment retrieval uses a sequential attachment ID without confirming ownership. The reported result is instance-wide attachment download and deletion.
Likely exposure
Self-hosted Vikunja deployments before 2.2.1 are the likely exposure, especially instances using link sharing and file attachments. Internet-accessible instances carry higher operational risk. The source bundle does not identify affected hosted services beyond Vikunja itself.
Exploitation context
The CVE is not listed as KEV in the bundle, and no cited source confirms active exploitation. The reported CVSS is 9.8 with network access, low complexity, no privileges, and no user interaction, making rapid remediation appropriate despite incomplete exploitation evidence.
Researcher notes
This is reported as CWE-639 authorization bypass through IDOR. The source bundle supports the endpoint names, vulnerable behavior, CVSS, and version boundary. It does not provide safe detection logic, exploit telemetry, or detailed patch diff evidence.
Mitigation direction
- Upgrade Vikunja to version 2.2.1 or later.
- Review the vendor GitHub advisory for current fix guidance.
- Restrict external access to vulnerable Vikunja instances until upgraded.
- Audit link shares and revoke unnecessary shares.
- Back up and review attachment storage for unexpected deletion or access.
Validation and detection
- Inventory Vikunja instances and confirm exact running versions.
- Identify instances below 2.2.1 as vulnerable.
- Check whether link sharing and task attachments are enabled or used.
- Review access logs for unusual attachment enumeration or deletion patterns.
- Confirm upgraded instances no longer expose the vulnerable behavior.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-639: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2026-56765 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Critical
- CVSS
- 9.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
SSVC decision data
CVSS vector scores
2 official scoresWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H3.95.9VulnCheckCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N——VulnCheckVulnerability scoring details
Base CVSS 4.0 score
9.3CriticalVector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Base CVSS 3.1 score
9.8CriticalVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- GitHub Security Advisory (GHSA-2pv8-4c52-mf8j)CVE reference, VulnCheck · vendor-advisory
- VulnCheck Advisory: Vikunja - Unauthenticated Instance-Wide Data Breach via Link Share Hash Disclosure Chained with Cross-Project Attachment IDORCVE reference, VulnCheck · third-party-advisory
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Authorization Bypass Through User-Controlled Key
Authorization Bypass Through User-Controlled Key represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.