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NVD / CVE Program· CNA EEF

CVE-2026-86688: Session id is not renewed on authentication in ash_authentication, allowing session fixation

Noroxi assessment

Priority: Monitor (action score 29/100)

  • 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: 0.74% (FIRST EPSS); higher than 54.9% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No special conditions are required; it is repeatable.
  • Fixed version: team-alembic ash_authentication 3e1d452cbf1564e87f5f97be882b66fe25af7cfa, 4.15.0, 5.0.0-rc.14.

Low priority for now. Upgrade to team-alembic ash_authentication 3e1d452cbf1564e87f5f97be882b66fe25af7cfa, 4.15.0, 5.0.0-rc.14 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

Session Fixation vulnerability in team-alembic ash_authentication allows an attacker who can plant a session identifier in a victim's browser to hold an authenticated session once that victim signs in. AshAuthentication.Plug.Helpers.store_in_session/2 writes the authenticated subject into the existing session with Plug.Conn.put_session/3 and never calls Plug.Conn.configure_session(renew: true), so the identifier the visitor arrived with carries into their authenticated session. Every authentication event reaches this one function: the default success/4 injected by AshAuthentication.Phoenix.Controller.__using__/1, the AuthController emitted by mix ash_authentication_phoenix.install, and remember-me auto-login. AshAuthentication.Phoenix.Plug.store_in_session/2 is a defdelegate to it. Logout does not close the window either, because clear_session/2 ends with Plug.Conn.clear_session/1, which clears session contents but leaves the identifier intact, so a planted identifier survives a logout-then-login cycle. This issue affects ash_authentication: from 0.2.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14.

HighCVSS 7.4 · v4.0—No exploit Fix available
Published
Sep 17, 2026
Updated
Sep 18, 2026
EPSS
0.7% · 54th percentile

Report tools

JSON

Action score

29

Monitor

Low priority for now.

CVSS
29 / 40 · 7.4 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.7%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · EEF
7.4
NVD has not scored this yet; the score shown is the CNA’s.

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

Get told when this record changes

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

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When you'll hear from us

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  • 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

    • 0.2.0 and later · before 4.15.0affected · semver
    • 5.0.0-rc.0 and later · before 5.0.0-rc.14affected · semver
    • a939dde9b917c072cdf10c4b0913a9886a4b0231 and lateraffected · gitfixed in 872db454405ecad4fcdabd9ff3d8755d1d6a69ae, 3e1d452cbf1564e87f5f97be882b66fe25af7cfa

Package-level exposure

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

EcosystemPackageAffected rangeFix
Hexash_authenticationfrom 0.2.0 · 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-2026-86522Sep 17, 2026 · Log injection via an unescaped password reset identity in AshAuthentication
    25Monitor
  • ← EarlierCVE-2026-86533Sep 17, 2026 · Revoked session accepted because the session jti is never checked in AshAuthentication and AshAuthentication Phoenix
    36Monitor
  • Later →CVE-2026-118505Nov 3, 2026 · AshAuthentication brute_force_strategy does not limit sign-in and request actions defined on the resource
    25Monitor

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_authentication3e1d452cbf1564e87f5f97be882b66fe25af7cfaVendor (CNA)
team-alembic ash_authentication4.15.0Vendor (CNA)
team-alembic ash_authentication5.0.0-rc.14Vendor (CNA)
team-alembic ash_authentication872db454405ecad4fcdabd9ff3d8755d1d6a69aeVendor (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.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
Integrity
Availability
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
A
Scope
X

Weakness class (CWE)

CWE-384 · Session Fixation

CVSS vector

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

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (5 more)

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

All records