CVE-2026-21879Public exploitNetwork attack vector

Cross-domain redirect via protocol-relative session URL

Published Jan 8, 2026 · Updated Jan 8, 2026

Open redirect in Kanboard 1.2.48 and earlier allows remote attackers to send users to an attacker-controlled site after login. The redirectAfterLogin method treats FILTER_VALIDATE_URL rejection as permission to redirect, so a protocol-relative session URL such as //evil.com reaches Response::redirect. Exploitation requires a user to open the crafted Kanboard URL and complete authentication; the resulting cross-domain redirect supports phishing or credential capture.

CVSS severity6.1
Medium
EPSS probability0.30%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Open redirect in Kanboard 1.2.48 and earlier allows remote attackers to send users to an attacker-controlled site after login. The redirectAfterLogin method treats FILTER_VALIDATE_URL rejection as permission to redirect, so a protocol-relative session URL such as //evil.com reaches Response::redirect. Exploitation requires a user to open the crafted Kanboard URL and complete authentication; the resulting cross-domain redirect supports phishing or credential capture.

The record

CVE
CVE-2026-21879
Published
Jan 8, 2026
Updated
Jan 8, 2026
Vendor
Kanboard
Product
Kanboard
Classifications
CWE-601, T1204.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 8, 2026CVE publishedPublication date reported by the CVE source.
  2. Jan 8, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 1.2.49

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Kanboard · Kanboardversion=< 1.2.49

Published CVSS scores

6.1NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
4.7GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-601URL Redirection to Untrusted Site ('Open Redirect')
T1204.001User Execution: Malicious Link

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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