CVE-2026-76949 (GCVE-0-2026-76949)
Vulnerability from cvelistv5 – Published: 2026-09-17 21:57 – Updated: 2026-09-18 14:31
VLAI
EPSS
VEX
Title
Remember-me sign-in guard reads a session key that is never written in ash_authentication, allowing session replacement
Summary
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.
Severity
SSVC
Exploitation: none
Automatable: yes
Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-18 14:24 UTC
CWE
- CWE-290 - Authentication Bypass by Spoofing
Assigner
References
6 references
Impacted products
2 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| team-alembic | ash_authentication |
Affected:
4.10.0 , < 4.15.0
(semver)
Affected: 5.0.0-rc.0 , < 5.0.0-rc.14 (semver) cpe:2.3:a:team-alembic:ash_authentication:*:*:*:*:*:*:*:* |
||
| team-alembic | ash_authentication |
Affected:
3d3de314692558d06ec13945f857f00514e95a8c , < *
(git)
cpe:2.3:a:team-alembic:ash_authentication:*:*:*:*:*:*:*:* |
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"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"type": "Secondary"
}
],
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"id": "CVE-2026-76949",
"options": [
{
"exploitation": "none"
},
{
"automatable": "yes"
},
{
"technicalImpact": "total"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-09-18T14:24:28.652087Z",
"version": "2.0.3"
}
}
]
},
"published": "2026-09-17T22:17:03.883",
"references": [
{
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"url": "https://cna.erlef.org/cves/CVE-2026-76949.html"
},
{
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"url": "https://github.com/team-alembic/ash_authentication/commit/3d3de314692558d06ec13945f857f00514e95a8c"
},
{
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"url": "https://github.com/team-alembic/ash_authentication/commit/9a34136b844abe179da1075067cf2835c64dcc12"
},
{
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"url": "https://github.com/team-alembic/ash_authentication/commit/b9568a53b438247238b1c5a4f49c8d84650f4bba"
},
{
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"url": "https://github.com/team-alembic/ash_authentication/security/advisories/GHSA-hh34-374j-pfr5"
},
{
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"url": "https://osv.dev/vulnerability/EEF-CVE-2026-76949"
}
],
"sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"vulnStatus": "Deferred",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-290"
}
],
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"type": "Secondary"
}
]
}
},
"vulnrichment": {
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-76949",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "yes"
},
{
"Technical Impact": "total"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-09-18T14:24:28.652087Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-09-18T14:29:29.773Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"collectionURL": "https://repo.hex.pm",
"cpes": [
"cpe:2.3:a:team-alembic:ash_authentication:*:*:*:*:*:*:*:*"
],
"defaultStatus": "unaffected",
"modules": [
"\u0027Elixir.AshAuthentication.Plug.Helpers\u0027"
],
"packageName": "ash_authentication",
"packageURL": "pkg:hex/ash_authentication",
"product": "ash_authentication",
"programFiles": [
"lib/ash_authentication/plug/helpers.ex"
],
"programRoutines": [
{
"name": "\u0027Elixir.AshAuthentication.Plug.Helpers\u0027:sign_in_using_remember_me/3"
},
{
"name": "\u0027Elixir.AshAuthentication.Plug.Helpers\u0027:store_in_session/2"
}
],
"repo": "https://github.com/team-alembic/ash_authentication",
"vendor": "team-alembic",
"versions": [
{
"lessThan": "4.15.0",
"status": "affected",
"version": "4.10.0",
"versionType": "semver"
},
{
"lessThan": "5.0.0-rc.14",
"status": "affected",
"version": "5.0.0-rc.0",
"versionType": "semver"
}
]
},
{
"collectionURL": "https://github.com",
"cpes": [
"cpe:2.3:a:team-alembic:ash_authentication:*:*:*:*:*:*:*:*"
],
"defaultStatus": "unaffected",
"modules": [
"\u0027Elixir.AshAuthentication.Plug.Helpers\u0027"
],
"packageName": "team-alembic/ash_authentication",
"packageURL": "pkg:github/team-alembic/ash_authentication",
"product": "ash_authentication",
"programFiles": [
"lib/ash_authentication/plug/helpers.ex"
],
"programRoutines": [
{
"name": "\u0027Elixir.AshAuthentication.Plug.Helpers\u0027:sign_in_using_remember_me/3"
},
{
"name": "\u0027Elixir.AshAuthentication.Plug.Helpers\u0027:store_in_session/2"
}
],
"repo": "https://github.com/team-alembic/ash_authentication",
"vendor": "team-alembic",
"versions": [
{
"changes": [
{
"at": "b9568a53b438247238b1c5a4f49c8d84650f4bba",
"status": "unaffected"
},
{
"at": "9a34136b844abe179da1075067cf2835c64dcc12",
"status": "unaffected"
}
],
"lessThan": "*",
"status": "affected",
"version": "3d3de314692558d06ec13945f857f00514e95a8c",
"versionType": "git"
}
]
}
],
"configurations": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003eThe application must enable the \u003ccode\u003eremember_me\u003c/code\u003e strategy and run its per-request plug in the browser pipeline, with \u003ccode\u003erequire_token_presence_for_authentication?\u003c/code\u003e at its default of \u003ccode\u003efalse\u003c/code\u003e. Enabling that setting makes the guard read the key the session actually holds, which closes the issue.\u003c/p\u003e\n\u003cp\u003eThe attacker also needs a position from which to set a cookie in the victim\u0027s browser, such as cookie tossing from a sibling subdomain, an HTTP host without HSTS, or a shared or kiosk browser.\u003c/p\u003e"
},
{
"base64": false,
"type": "text/markdown",
"value": "The application must enable the `remember_me` strategy and run its per-request plug in the browser pipeline, with `require_token_presence_for_authentication?` at its default of `false`. Enabling that setting makes the guard read the key the session actually holds, which closes the issue.\n\nThe attacker also needs a position from which to set a cookie in the victim\u0027s browser, such as cookie tossing from a sibling subdomain, an HTTP host without HSTS, or a shared or kiosk browser."
}
],
"value": "The application must enable the remember_me strategy and run its per-request plug in the browser pipeline, with require_token_presence_for_authentication? at its default of false. Enabling that setting makes the guard read the key the session actually holds, which closes the issue.\n\nThe attacker also needs a position from which to set a cookie in the victim\u0027s browser, such as cookie tossing from a sibling subdomain, an HTTP host without HSTS, or a shared or kiosk browser."
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:a:team-alembic:ash_authentication:*:*:*:*:*:*:*:*",
"versionEndExcluding": "4.15.0",
"versionStartIncluding": "4.10.0",
"vulnerable": true
},
{
"criteria": "cpe:2.3:a:team-alembic:ash_authentication:*:*:*:*:*:*:*:*",
"versionEndExcluding": "5.0.0-rc.14",
"versionStartIncluding": "5.0.0-rc.0",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
],
"operator": "AND"
}
],
"credits": [
{
"lang": "en",
"type": "reporter",
"value": "Peter Ullrich"
},
{
"lang": "en",
"type": "remediation developer",
"value": "James Harton"
},
{
"lang": "en",
"type": "coordinator",
"value": "Jonatan M\u00e4nnchen / EEF"
}
],
"dateAssigned": "2026-09-17T14:23:56.000Z",
"descriptions": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003eAuthentication Bypass by Spoofing vulnerability in team-alembic ash_authentication allows an attacker who can plant a remember-me cookie in a victim\u0027s browser to replace that victim\u0027s authenticated session with one for the attacker\u0027s own account.\u003c/p\u003e\n\u003cp\u003e\u003ccode\u003eAshAuthentication.Plug.Helpers.sign_in_using_remember_me/3\u003c/code\u003e skips re-authenticating an already-signed-in visitor by checking the session for \u003ccode\u003e\"\u0026lt;subject_name\u0026gt;_token\"\u003c/code\u003e, but \u003ccode\u003estore_in_session/2\u003c/code\u003e writes that key only when \u003ccode\u003erequire_token_presence_for_authentication?\u003c/code\u003e 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 \u003ccode\u003eauthenticate_resource_from_session/4\u003c/code\u003e selects the key correctly, so the guard and the reader disagree about which key holds the session.\u003c/p\u003e\n\u003cp\u003eThis 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.\u003c/p\u003e"
},
{
"base64": false,
"type": "text/markdown",
"value": "Authentication Bypass by Spoofing vulnerability in team-alembic ash_authentication allows an attacker who can plant a remember-me cookie in a victim\u0027s browser to replace that victim\u0027s authenticated session with one for the attacker\u0027s own account.\n\n`AshAuthentication.Plug.Helpers.sign_in_using_remember_me/3` skips re-authenticating an already-signed-in visitor by checking the session for `\"\u003csubject_name\u003e_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.\n\nThis 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."
}
],
"value": "Authentication Bypass by Spoofing vulnerability in team-alembic ash_authentication allows an attacker who can plant a remember-me cookie in a victim\u0027s browser to replace that victim\u0027s authenticated session with one for the attacker\u0027s own account.\n\nAshAuthentication.Plug.Helpers.sign_in_using_remember_me/3 skips re-authenticating an already-signed-in visitor by checking the session for \"\u003csubject_name\u003e_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.\n\nThis 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."
}
],
"impacts": [
{
"capecId": "CAPEC-21",
"descriptions": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003eAn attacker who can set a remember-me cookie in a victim\u0027s browser silently replaces the victim\u0027s authenticated session with one for the attacker\u0027s own account, so data the victim subsequently enters is written to records the attacker controls. The victim is given no indication their identity changed.\u003c/p\u003e"
},
{
"base64": false,
"type": "text/markdown",
"value": "An attacker who can set a remember-me cookie in a victim\u0027s browser silently replaces the victim\u0027s authenticated session with one for the attacker\u0027s own account, so data the victim subsequently enters is written to records the attacker controls. The victim is given no indication their identity changed."
}
],
"value": "An attacker who can set a remember-me cookie in a victim\u0027s browser silently replaces the victim\u0027s authenticated session with one for the attacker\u0027s own account, so data the victim subsequently enters is written to records the attacker controls. The victim is given no indication their identity changed."
}
]
}
],
"metrics": [
{
"cvssV4_0": {
"Automatable": "NOT_DEFINED",
"Recovery": "NOT_DEFINED",
"Safety": "NOT_DEFINED",
"attackComplexity": "LOW",
"attackRequirements": "PRESENT",
"attackVector": "NETWORK",
"baseScore": 9.1,
"baseSeverity": "CRITICAL",
"privilegesRequired": "NONE",
"providerUrgency": "NOT_DEFINED",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
"userInteraction": "NONE",
"valueDensity": "NOT_DEFINED",
"vectorString": "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",
"version": "4.0",
"vulnAvailabilityImpact": "NONE",
"vulnConfidentialityImpact": "HIGH",
"vulnIntegrityImpact": "HIGH",
"vulnerabilityResponseEffort": "NOT_DEFINED"
},
"format": "CVSS",
"scenarios": [
{
"lang": "en",
"value": "GENERAL"
}
]
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-290",
"description": "CWE-290 Authentication Bypass by Spoofing",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-09-17T21:57:50.146Z",
"orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"shortName": "EEF"
},
"references": [
{
"name": "GitHub Advisory",
"tags": [
"related",
"vendor-advisory"
],
"url": "https://github.com/team-alembic/ash_authentication/security/advisories/GHSA-hh34-374j-pfr5"
},
{
"name": "EEF CNA record for CVE-2026-76949",
"tags": [
"related"
],
"url": "https://cna.erlef.org/cves/CVE-2026-76949.html"
},
{
"name": "OSV record EEF-CVE-2026-76949",
"tags": [
"related"
],
"url": "https://osv.dev/vulnerability/EEF-CVE-2026-76949"
},
{
"name": "Introducing commit 3d3de31 in team-alembic/ash_authentication",
"tags": [
"related"
],
"url": "https://github.com/team-alembic/ash_authentication/commit/3d3de314692558d06ec13945f857f00514e95a8c"
},
{
"name": "Fix commit b9568a5 in team-alembic/ash_authentication",
"tags": [
"patch"
],
"url": "https://github.com/team-alembic/ash_authentication/commit/b9568a53b438247238b1c5a4f49c8d84650f4bba"
},
{
"name": "Fix commit 9a34136 in team-alembic/ash_authentication",
"tags": [
"patch"
],
"url": "https://github.com/team-alembic/ash_authentication/commit/9a34136b844abe179da1075067cf2835c64dcc12"
}
],
"source": {
"discovery": "EXTERNAL"
},
"title": "Remember-me sign-in guard reads a session key that is never written in ash_authentication, allowing session replacement",
"workarounds": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003eSet \u003ccode\u003erequire_token_presence_for_authentication? true\u003c/code\u003e on the authenticated resource\u0027s token configuration. \u003ccode\u003estore_in_session/2\u003c/code\u003e then writes the key the guard reads, so the already-signed-in branch fires and the remember-me sign-in no longer runs against a live session. Note this changes session storage semantics for the whole application and requires a token resource.\u003c/p\u003e\n\u003cp\u003eOtherwise remove the remember-me plug from the browser pipeline, which disables remember-me auto-login entirely.\u003c/p\u003e"
},
{
"base64": false,
"type": "text/markdown",
"value": "Set `require_token_presence_for_authentication? true` on the authenticated resource\u0027s token configuration. `store_in_session/2` then writes the key the guard reads, so the already-signed-in branch fires and the remember-me sign-in no longer runs against a live session. Note this changes session storage semantics for the whole application and requires a token resource.\n\nOtherwise remove the remember-me plug from the browser pipeline, which disables remember-me auto-login entirely."
}
],
"value": "Set require_token_presence_for_authentication? true on the authenticated resource\u0027s token configuration. store_in_session/2 then writes the key the guard reads, so the already-signed-in branch fires and the remember-me sign-in no longer runs against a live session. Note this changes session storage semantics for the whole application and requires a token resource.\n\nOtherwise remove the remember-me plug from the browser pipeline, which disables remember-me auto-login entirely."
}
]
}
},
"cveMetadata": {
"assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"assignerShortName": "EEF",
"cveId": "CVE-2026-76949",
"datePublished": "2026-09-17T21:57:50.146Z",
"dateReserved": "2026-09-17T05:30:01.744Z",
"dateUpdated": "2026-09-18T14:31:41.806Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
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Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.
Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Vulnerability timeline
Sightings and recorded dates, grouped by day · UTC
How durations are calculated
Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.
Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.