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CVE Record

CVE-2026-45368: Kirby: Cross-site scripting (XSS) from links in KirbyTags and image blocks in the site frontend

Kirby is an open-source content management system. In versions prior to 4.9.1 and 5.4.1, the underlying URL methods for the KirbyTags and image blocks components did not filter out malicious URL values that resolve to script execution. The vulnerability affects four first-party Kirby renderers that produce `<a href="…">` output from editor-supplied field values: the (`link: …)` KirbyTag, the `link`: parameter of the `(image: …)` KirbyTag when it does not resolve to a known file or `self`, the `link` field of the built-in image block, and the HTML importer for the `blocks` field (which accepted the same malicious input as the image block `link` field). While simple `avascript:` URLs were already deactivated by treating them as a relative path and prepending a single slash to the URL, the use of URLs of the format `javascript://x%0A…` bypasses this protection. The `vbscript:`, `data:`, `livescript:`, `mocha:` and `jar:` schemes are affected by the same underlying gap. This issue has been fixed in versions 4.9.1 and 5.4.1.

HighCVSS 8.4Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

Kirby CMS sites on affected versions can render malicious editor-supplied links as executable browser content. This can let an attacker with content-editing access place a dangerous link in frontend pages. The main business risk is compromise of visitor or admin browser sessions through stored XSS.

Executive priority

Treat as a high-priority patch for any Kirby site with delegated content editing. It is not described as actively exploited in the supplied sources, but stored XSS on public pages can create meaningful account, brand, and visitor risk.

Technical view

CVE-2026-45368 is a CWE-79 XSS flaw in Kirby URL handling for selected KirbyTags, image block links, and blocks HTML import. Malicious URL schemes were not fully filtered before rendering anchor href output. Fixed versions are 4.9.1 and 5.4.1.

Likely exposure

Exposure is likely for Kirby sites below 4.9.1, or 5.x sites below 5.4.1, that use affected link or image content features. Risk is higher where non-admin or lower-trust users can edit content or import HTML blocks.

Exploitation context

The source bundle does not show KEV listing or active exploitation. Exploitation requires editor-supplied malicious link values and user activation in the frontend. The advisory indicates multiple script-capable URL schemes were affected by the same filtering gap.

Researcher notes

Focus validation on first-party renderers producing anchor href output from editor-controlled fields. Affected areas are link KirbyTag, image KirbyTag link fallback behavior, built-in image block link field, and blocks HTML importer. Avoid assuming third-party plugins are affected without separate evidence.

Mitigation direction

  • Upgrade Kirby 4.x deployments to 4.9.1 or later.
  • Upgrade Kirby 5.x deployments to 5.4.1 or later.
  • Review vendor advisory and release notes before production rollout.
  • Restrict content editing to trusted users until patched.
  • Audit existing KirbyTags, image blocks, and imported blocks for unsafe link schemes.

Validation and detection

  • Inventory Kirby versions across all public and internal sites.
  • Check whether affected KirbyTags, image block links, or block HTML import are used.
  • Confirm deployed version is 4.9.1, 5.4.1, or newer.
  • Review content repositories or panel data for suspicious non-web link schemes.
  • Verify frontend pages no longer render unsafe href values after upgrade.
Prepared
Confidence
high
Sources
4

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

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 · medium confidence lookup

CWE-79: User-session and phishing behavior lookup

Client-side and session-facing weaknesses should be reviewed alongside initial-access and user-execution behaviors. 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.

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cve · low confidence lookup

CVE-2026-45368 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
8.4 (4.0)
Known Exploited
No
Published

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

Official CVE source material

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.

1CVSS vectors
3Timeline events
1ADP providers
3Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

CVSS vector scores

1 official score

We 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.

ScoreVersionSeverityVectorExploitImpactSource
8.4CVSS 4.0HighCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N——GitHub_M

Vulnerability scoring details

Base CVSS 4.0 score

8.4High
CVSS 4.0 vector shape for CVE-2026-45368Attack VectorAttack ComplexityAttack RequirementsPrivileges RequiredUser InteractionVS ConfidentialityVS IntegrityVS AvailabilitySS ConfidentialitySS IntegritySS Availability

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Attack Requirements
NonePresent
Privileges Required
NoneLowHigh
User Interaction
NonePassiveActive
VS Confidentiality
HighLowNone
VS Integrity
HighLowNone
VS Availability
HighLowNone
SS Confidentiality
HighLowNone
SS Integrity
HighLowNone
SS Availability
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
getkirbykirby< 4.9.1, >= 5.0.0, < 5.4.1Listed
Weakness

CWE details

CWE-79

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-79 · source CWE mapping

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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