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NVD / CVE Program· CNA EEF

CVE-2026-76949: Remember-me sign-in guard reads a session key that is never written in ash_authentication, allowing session replacement

Noroxi assessment

Priority: Monitor (action score 36/100)

  • 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: 0.77% (FIRST EPSS); higher than 55.8% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • According to CISA the attack is automatable: targets can be found by mass scanning.
  • Fixed version: team-alembic ash_authentication 4.15.0, 5.0.0-rc.14, 9a34136b844abe179da1075067cf2835c64dcc12.

Low priority for now. Upgrade to team-alembic ash_authentication 4.15.0, 5.0.0-rc.14, 9a34136b844abe179da1075067cf2835c64dcc12 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

Authentication Bypass by Spoofing vulnerability in team-alembic ash_authentication allows an attacker who can plant a remember-me cookie in a victim's browser to replace that victim's authenticated session with one for the attacker's own account. AshAuthentication.Plug.Helpers.sign_in_using_remember_me/3 skips re-authenticating an already-signed-in visitor by checking the session for "<subject_name>_token", but store_in_session/2 writes that key only when require_token_presence_for_authentication? is enabled and otherwise writes the bare subject name. At the default setting the guard therefore reads a key that is never written, its already-signed-in branch is unreachable, and the remember-me sign-in runs on every request through the per-request browser pipeline plug. A planted remember-me cookie is consequently honoured even for a visitor holding a live authenticated session, so whatever the victim enters afterwards lands in data the attacker controls. The read path in authenticate_resource_from_session/4 selects the key correctly, so the guard and the reader disagree about which key holds the session. This issue affects ash_authentication: from 4.10.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14.

CriticalCVSS 9.1 · v4.0—No exploit Fix available
Published
Sep 17, 2026
Updated
Sep 18, 2026
EPSS
0.7% · 55th percentile

Report tools

JSON

Action score

36

Monitor

Low priority for now.

CVSS
36 / 40 · 9.1 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.7%

CISA SSVC decision

Exploitation
none
Automatable
yes
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · EEF
9.1
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:N/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

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

Follow CVE-2026-76949

When you'll hear from us

  • when it enters CISA KEV
  • 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

    • 4.10.0 and later · before 4.15.0affected · semver
    • 5.0.0-rc.0 and later · before 5.0.0-rc.14affected · semver
    • 3d3de314692558d06ec13945f857f00514e95a8c and lateraffected · gitfixed in b9568a53b438247238b1c5a4f49c8d84650f4bba, 9a34136b844abe179da1075067cf2835c64dcc12

Package-level exposure

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

EcosystemPackageAffected rangeFix
Hexash_authenticationfrom 4.10.0 · 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-2026-91039dynamic_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
  • CVE-2026-86533Revoked session accepted because the session jti is never checked in AshAuthentication and AshAuthentication Phoenix
    36Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2026-85500Sep 17, 2026 · `require_confirmed_with` is not enforced on the action and fails open on an unreadable attribute in AshAuthentication
    36Monitor
  • ← EarlierCVE-2026-86522Sep 17, 2026 · Log injection via an unescaped password reset identity in AshAuthentication
    25Monitor
  • Later →CVE-2026-86688Sep 17, 2026 · Session id is not renewed on authentication in ash_authentication, allowing session fixation
    29Monitor

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_authentication9a34136b844abe179da1075067cf2835c64dcc12Vendor (CNA)
team-alembic ash_authenticationb9568a53b438247238b1c5a4f49c8d84650f4bbaVendor (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-2026-910390 days apartdynamic_oidc identities are not namespaced by connection in ash_authentication, allowing cross-connection account takeover
    36Monitor
  • CVE-2026-4975794 days apartOAuth2/OIDC account takeover in AshAuthentication via email-based user matching
    36Monitor

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 user action 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
None
Scope
X

Weakness class (CWE)

CWE-290 · Authentication Bypass by Spoofing

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/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✗ → ✓

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References

Show all references (5 more)

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

All records