authd: Account takeover via username fallback in identity matching after IdP email reassignment

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-102631
StatePUBLISHED
Assignercanonical
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-15 17:17:10 UTC
Updated2026-10-16 21:17:11 UTC
DescriptionIn authd before 0.7.1, the user identity matching in UpdateUser (internal/users/manager.go) resolves an incoming login by the broker-scoped provider ID, but falls back to matching the username when the provider ID does not belong to any known user, and does not reject a conflicting non-empty provider ID. If an identity provider reassigns an email address, which authd uses as the username, to a new account, the new account inherits the previous user's local UID and home directory on its next login. This allows the new user to access and modify files belonging to the previous user, including credentials such as SSH keys and cloud API tokens, and silently rebinds the local account record to the new identity. As a mitigation, administrators should lock or delete the previous user's local authd account when the corresponding IdP account is removed.

Risk And Classification

Primary CVSS: v4.0 5.9 MEDIUM from [email protected]

CVSS:4.0/AV:L/AC:H/AT:P/PR:N/UI:N/VC:H/VI:L/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

Problem Types: CWE-287 | CWE-287 CWE-287 Improper Authentication

VersionSourceTypeScoreSeverityVector
4.0[email protected]Secondary5.9MEDIUMCVSS:4.0/AV:L/AC:H/AT:P/PR:N/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/C...
4.0CNACVSS5.9MEDIUMCVSS:4.0/AV:L/AC:H/AT:P/PR:N/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N

CVSS v4.0 Breakdown

Attack Vector
Local
Attack Complexity
High
Attack Requirements
Present
Privileges Required
None
User Interaction
None
Confidentiality
High
Integrity
Low
Availability
None
Sub Conf.
None
Sub Integrity
None
Sub Availability
None

CVSS:4.0/AV:L/AC:H/AT:P/PR:N/UI:N/VC:H/VI:L/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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Canonical Authd affected 0.1 0.7.1 custom Linux
CNA Canonical Authd affected 0.1 0.7.1~ubuntu24.04.1 custom Linux
CNA Canonical Authd affected 0.1 0.7.1~ubuntu26.04 custom Linux

References

ReferenceSourceLinkTags
ubuntu.com/security/CVE-2026-102631 [email protected] ubuntu.com
github.com/canonical/authd/pull/2067 [email protected] github.com
bugs.launchpad.net/ubuntu/+source/authd/+bug/2168531 [email protected] bugs.launchpad.net
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Ali Mashally (en)

CNA: Adrian Dombeck (en)

© CVE.report 2026

Use of this information constitutes acceptance for use in an AS IS condition. There are NO warranties, implied or otherwise, with regard to this information or its use. Any use of this information is at the user's risk. It is the responsibility of user to evaluate the accuracy, completeness or usefulness of any information, opinion, advice or other content. EACH USER WILL BE SOLELY RESPONSIBLE FOR ANY consequences of his or her direct or indirect use of this web site. ALL WARRANTIES OF ANY KIND ARE EXPRESSLY DISCLAIMED. This site will NOT BE LIABLE FOR ANY DIRECT, INDIRECT or any other kind of loss.

CVE, CWE, and OVAL are registred trademarks of The MITRE Corporation and the authoritative source of CVE content is MITRE's CVE web site. This site includes MITRE data granted under the following license.

Free CVE JSON API cve.report/api

CVE.report and Source URL Uptime Status status.cve.report