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NVD / CVE Program· CNA EEF

CVE-2026-81637: Replayable OAuth2 CSRF state retained after a failed callback in AshAuthentication

LowCVSS 2.3 · v4.0—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 9/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.60% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. No account or password is required. Special conditions such as timing or configuration are required.
  • Fixed version: team-alembic ash_authentication 4.15.0, 5.0.0-rc.14, bd4352303bc9d72d007f6818775267585a4bcc2f.

Low priority for now. Upgrade to team-alembic ash_authentication 4.15.0, 5.0.0-rc.14, bd4352303bc9d72d007f6818775267585a4bcc2f or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

Insufficient Session Expiration vulnerability in team-alembic AshAuthentication allows an attacker who obtains a victim's OAuth2 state value to replay the callback and sign that victim into an attacker-controlled account. AshAuthentication.Strategy.OAuth2.Plug.callback/2 clears the stored session_params through a rebinding step inside its with chain, conn <- delete_session(conn, session_key). Elixir evaluates the else block in the scope enclosing the with, so every failure path (the provider returning ?error=access_denied, an invalid code, a token-exchange error, or a registration or sign-in failure) reaches store_authentication_result/2 holding the original connection and the session entry is never removed. The value the module's own comment describes as protection against a CSRF-related attack is therefore consumed only when authentication succeeds, and survives a cancelled or failed attempt until the next request phase or session expiry. This issue affects ash_authentication: from 0.6.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14.

Published
Sep 17, 2026
Updated
Sep 18, 2026
EPSS
0.6% · 49th percentile

Report tools

JSON

Action score

9

Monitor

Low priority for now.

CVSS
9 / 40 · 2.3 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.6%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · EEF
2.3
NVD has not scored this yet; the score shown is the CNA’s.

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

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

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  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2026-81637

When you'll hear from us

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  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (EEF). Independent of NVD's CPE analysis and usually ahead of it.

  • team-alembic ash_authentication

    • 0.6.0 and later · before 4.15.0affected · semver
    • 5.0.0-rc.0 and later · before 5.0.0-rc.14affected · semver
    • c5f589058e04239263f50a1430eb17ea6d5dd1a2 and lateraffected · gitfixed in bd4352303bc9d72d007f6818775267585a4bcc2f, d7f939cd02bd618bcaa304631846fa75ffc419d7

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Hexash_authenticationfrom 0.6.0 · before 4.15.04.15.0
Hexash_authenticationfrom 5.0.0-rc.0 · before 5.0.0-rc.145.0.0-rc.14

Same product

team-alembic: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-76949Remember-me sign-in guard reads a session key that is never written in ash_authentication, allowing session replacement
    36Monitor
  • CVE-2026-91039dynamic_oidc identities are not namespaced by connection in ash_authentication, allowing cross-connection account takeover
    36Monitor
  • CVE-2026-88952OAuth2 sign-in attached to an existing account without an email comparison in AshAuthentication
    36Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2026-78223Sep 17, 2026 · Token revocation record built from unverified JWT claims in AshAuthentication
    27Monitor
  • ← EarlierCVE-2026-80218Sep 17, 2026 · Sign-in token minted for one resource accepted by another in AshAuthentication
    30Monitor
  • Later →CVE-2026-82685Sep 17, 2026 · Confirmation token accepted on any record in AshAuthentication
    30Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
team-alembic ash_authentication4.15.0Vendor (CNA)
team-alembic ash_authentication5.0.0-rc.14Vendor (CNA)
team-alembic ash_authenticationbd4352303bc9d72d007f6818775267585a4bcc2fVendor (CNA)
team-alembic ash_authenticationd7f939cd02bd618bcaa304631846fa75ffc419d7Vendor (CNA)
Hex:ash_authentication4.15.0Package registry (OSV)
Hex:ash_authentication5.0.0-rc.14Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-865330 days apartRevoked session accepted because the session jti is never checked in AshAuthentication and AshAuthentication Phoenix
    36Monitor

Not on record for this CVE: public bounty program.

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • Special conditions such as timing or configuration are required.

If successful

Confidentiality
Integrity
Availability
Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
P
Scope
X

Weakness class (CWE)

CWE-613 · Insufficient Session Expiration

CVSS vector

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

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

References

Show all references (5 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records