authd: Account takeover via username fallback in identity matching after IdP email reassignment
In 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.
CVE-2026-102631
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-102631
authd
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"repo": "https://github.com/canonical/authd",
"vendor": "Canonical",
"product": "authd",
"versions": [
{
"status": "affected",
"version": "0.1",
"lessThan": "0.7.1",
"versionType": "custom"
},
{
"status": "affected",
"version": "0.1",
"lessThan": "0.7.1~ubuntu24.04.1",
"versionType": "custom"
},
{
"status": "affected",
"version": "0.1",
"lessThan": "0.7.1~ubuntu26.04",
"versionType": "custom"
}
],
"platforms": [
"Linux"
],
"packageName": "authd",
"defaultStatus": "unaffected"
}
]- Related CVEs
- CVE-2026-102631
Source reference:
/cveMetadata/cveId
Publisher severity
medium
Source reference: /containers/cna/metrics
- Event
- #34406 · Revision 1
- Added to Heist Feed
- Publisher date