CVE-2026-91039: team-alembic ash_authentication · Authentication Bypass by Spoofing
Affects team-alembic ash_authenticationSource CVE Database V5
Not known to be exploited · CVSS 9.1 Critical : upgrade to 5.0.0-rc.14 as a priority.
Data as of 1 Nov 2026, 11:03 UTC
- EPSS
- 0.6% chance of exploitation in 30 days – higher than 51% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 5.0.0-rc.14, 73ad16e452670bbf843550a13361bd41e72ad964
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:NExploitation evidence
Disclosed: evidence found.
CVE published 17 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 1 Nov 2026.
What to do
Upgrade ash_authentication to 5.0.0-rc.14; ash_authentication to 73ad16e452670bbf843550a13361bd41e72ad964.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| team-alembicash_authentication | Affected
| Fixed in
|
| team-alembicash_authentication | Affected
| Fixed in
|
Hexash_authenticationpkg:hex/ash_authenticationOther threats | Affected
| Fixed in
|
CPE configurations (1)
cpe:2.3:a:team-alembic:ash_authentication:*:*:*:*:*:*:*:*
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
If you cannot patch yet, avoid using affected versions (>=5.0.0-rc.10 <5.0.0-rc.14) in production environments or implement additional identity verification controls to mitigate the risk.
Description
Authentication Bypass by Spoofing vulnerability in team-alembic ash_authentication allows an attacker who operates one identity-provider connection of a dynamic_oidc strategy to be signed in as a local user established through a different connection. The strategy is meant to keep each connection in its own identity namespace by writing every UserIdentity row's strategy field as "<name>/<connection_id>", but that namespacing never takes effect. __connection_id__ is populated only on the ephemeral runtime struct built per request in dynamic_oidc/plug.ex, and DynamicOidc.IdentityChange.change/3 re-fetches the strategy from the compile-time DSL through Info.strategy_for_action, yielding the persisted struct whose __connection_id__ is its defstruct default of nil. OAuth2.identity_strategy_name/1 therefore falls back to the bare strategy name for both the identity write and the reads in oauth2/user_resolver.ex and oauth2/sign_in_preparation.ex. Since the identity resource's unique key is (uid, strategy), one row exists per sub across every connection, and the identity-match branch runs before any email check. Neither strategy handles iss, so nothing else distinguishes the issuers: OpenID Connect Core section 5.7 makes sub unique only within an issuer, so two connections numbering subjects independently share one subject space. This issue affects ash_authentication: from 5.0.0-rc.10 before 5.0.0-rc.14.
References
- github.com/team-alembic/ash_authentication/security/advisories/GHSA-73j9-m294-fvv9 (opens in a new tab)
- cna.erlef.org/cves/CVE-2026-91039.html (opens in a new tab)
- osv.dev/vulnerability/EEF-CVE-2026-91039 (opens in a new tab)
- github.com/team-alembic/ash_authentication/commit/64530644f9b37ebb76ca14aeb83a77597a0034b7 (opens in a new tab)
- github.com/team-alembic/ash_authentication/commit/73ad16e452670bbf843550a13361bd41e72ad964 (opens in a new tab)