CVE-2026-87853 (GCVE-0-2026-87853)
Vulnerability from cvelistv5 – Published: 2026-09-09 16:06 – Updated: 2026-09-10 14:56
VLAI
EPSS
VEX
Title
Sssd: sssd: idp authentication prefix comparison allows cross-user impersonation
Summary
A flaw was found in SSSD's IdP authentication provider. The eval_access_token_buf() function compares the OIDC subject identifier using strncmp() with the authenticated user's identifier length, performing a prefix comparison instead of an exact match. An attacker whose IdP identifier is a strict prefix of a target user's identifier can authenticate as the target user.
Severity
7.5 (High)
SSVC
Exploitation: none
Automatable: no
Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-09 18:28 UTC
CWE
- CWE-187 - Partial String Comparison
Assigner
References
2 references
| URL | Tags |
|---|---|
| https://access.redhat.com/security/cve/CVE-2026-87853 | vdb-entryx_refsource_REDHAT |
| https://bugzilla.redhat.com/show_bug.cgi?id=2530888 | issue-trackingx_refsource_REDHAT |
Impacted products
6 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Red Hat | Red Hat Enterprise Linux 10 |
cpe:/o:redhat:enterprise_linux:10
|
||
| Red Hat | Red Hat Enterprise Linux 6 |
cpe:/o:redhat:enterprise_linux:6
|
||
| Red Hat | Red Hat Enterprise Linux 7 |
cpe:/o:redhat:enterprise_linux:7
|
||
| Red Hat | Red Hat Enterprise Linux 8 |
cpe:/o:redhat:enterprise_linux:8
|
||
| Red Hat | Red Hat Enterprise Linux 9 |
cpe:/o:redhat:enterprise_linux:9
|
||
| Red Hat | Red Hat OpenShift Container Platform 4 |
cpe:/a:redhat:openshift:4
|
Date Public
2026-09-09 14:15
{
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-87853",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "no"
},
{
"Technical Impact": "total"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-09-09T18:28:46.606582Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-09-10T14:56:49.929Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
"cpes": [
"cpe:/o:redhat:enterprise_linux:10"
],
"defaultStatus": "affected",
"packageName": "sssd",
"product": "Red Hat Enterprise Linux 10",
"vendor": "Red Hat"
},
{
"collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
"cpes": [
"cpe:/o:redhat:enterprise_linux:6"
],
"defaultStatus": "unknown",
"packageName": "sssd",
"product": "Red Hat Enterprise Linux 6",
"vendor": "Red Hat"
},
{
"collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
"cpes": [
"cpe:/o:redhat:enterprise_linux:7"
],
"defaultStatus": "unaffected",
"packageName": "sssd",
"product": "Red Hat Enterprise Linux 7",
"vendor": "Red Hat"
},
{
"collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
"cpes": [
"cpe:/o:redhat:enterprise_linux:8"
],
"defaultStatus": "unaffected",
"packageName": "sssd",
"product": "Red Hat Enterprise Linux 8",
"vendor": "Red Hat"
},
{
"collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
"cpes": [
"cpe:/o:redhat:enterprise_linux:9"
],
"defaultStatus": "unaffected",
"packageName": "sssd",
"product": "Red Hat Enterprise Linux 9",
"vendor": "Red Hat"
},
{
"collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
"cpes": [
"cpe:/a:redhat:openshift:4"
],
"defaultStatus": "unaffected",
"packageName": "openshift/ose-rhel-coreos-8",
"product": "Red Hat OpenShift Container Platform 4",
"vendor": "Red Hat"
},
{
"collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
"cpes": [
"cpe:/a:redhat:openshift:4"
],
"defaultStatus": "unaffected",
"packageName": "openshift/ose-rhel-coreos-9",
"product": "Red Hat OpenShift Container Platform 4",
"vendor": "Red Hat"
}
],
"credits": [
{
"lang": "en",
"value": "Red Hat would like to thank Moritz Theile for reporting this issue."
}
],
"datePublic": "2026-09-09T14:15:45.513Z",
"descriptions": [
{
"lang": "en",
"value": "A flaw was found in SSSD\u0027s IdP authentication provider. The eval_access_token_buf() function compares the OIDC subject identifier using strncmp() with the authenticated user\u0027s identifier length, performing a prefix comparison instead of an exact match. An attacker whose IdP identifier is a strict prefix of a target user\u0027s identifier can authenticate as the target user."
}
],
"metrics": [
{
"other": {
"content": {
"namespace": "https://access.redhat.com/security/updates/classification/",
"value": "Moderate"
},
"type": "Red Hat severity rating"
}
},
{
"cvssV3_1": {
"attackComplexity": "HIGH",
"attackVector": "NETWORK",
"availabilityImpact": "HIGH",
"baseScore": 7.5,
"baseSeverity": "HIGH",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"privilegesRequired": "LOW",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"format": "CVSS"
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-187",
"description": "Partial String Comparison",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-09-09T16:06:25.638Z",
"orgId": "53f830b8-0a3f-465b-8143-3b8a9948e749",
"shortName": "redhat"
},
"references": [
{
"tags": [
"vdb-entry",
"x_refsource_REDHAT"
],
"url": "https://access.redhat.com/security/cve/CVE-2026-87853"
},
{
"name": "RHBZ#2530888",
"tags": [
"issue-tracking",
"x_refsource_REDHAT"
],
"url": "https://bugzilla.redhat.com/show_bug.cgi?id=2530888"
}
],
"timeline": [
{
"lang": "en",
"time": "2026-09-06T00:00:00.000Z",
"value": "Reported to Red Hat."
},
{
"lang": "en",
"time": "2026-09-09T14:15:45.513Z",
"value": "Made public."
}
],
"title": "Sssd: sssd: idp authentication prefix comparison allows cross-user impersonation",
"workarounds": [
{
"lang": "en",
"value": "Deployments not using the IdP authentication provider (idp_type = keycloak) are not affected. For affected deployments: (1) If using Keycloak LDAP federation, switching to Import Users: enabled mode causes Keycloak to assign random UUIDs as sub claims, making prefix collisions astronomically unlikely. (2) Restrict PAM login to specific users via simple_allow_users or access_provider = simple. (3) Disable Keycloak self-registration to prevent attackers from creating accounts with chosen prefix usernames."
}
],
"x_generator": {
"engine": "cvelib 1.8.0"
},
"x_redhatCweChain": "CWE-187: Partial String Comparison"
}
},
"cveMetadata": {
"assignerOrgId": "53f830b8-0a3f-465b-8143-3b8a9948e749",
"assignerShortName": "redhat",
"cveId": "CVE-2026-87853",
"datePublished": "2026-09-09T16:06:25.638Z",
"dateReserved": "2026-09-09T13:00:35.698Z",
"dateUpdated": "2026-09-10T14:56:49.929Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"epss": {
"cve": "CVE-2026-87853",
"date": "2026-09-10",
"epss": "0.00281",
"percentile": "0.20395"
},
"nvd": "{\"cve\":{\"id\":\"CVE-2026-87853\",\"sourceIdentifier\":\"secalert@redhat.com\",\"published\":\"2026-09-09T17:17:52.827\",\"lastModified\":\"2026-09-10T15:17:54.240\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"A flaw was found in SSSD\u0027s IdP authentication provider. The eval_access_token_buf() function compares the OIDC subject identifier using strncmp() with the authenticated user\u0027s identifier length, performing a prefix comparison instead of an exact match. An attacker whose IdP identifier is a strict prefix of a target user\u0027s identifier can authenticate as the target user.\"}],\"affected\":[{\"source\":\"secalert@redhat.com\",\"affectedData\":[{\"vendor\":\"Red Hat\",\"product\":\"Red Hat Enterprise Linux 10\",\"defaultStatus\":\"affected\",\"collectionURL\":\"https://access.redhat.com/downloads/content/package-browser/\",\"packageName\":\"sssd\",\"cpes\":[\"cpe:/o:redhat:enterprise_linux:10\"]},{\"vendor\":\"Red Hat\",\"product\":\"Red Hat Enterprise Linux 6\",\"defaultStatus\":\"unknown\",\"collectionURL\":\"https://access.redhat.com/downloads/content/package-browser/\",\"packageName\":\"sssd\",\"cpes\":[\"cpe:/o:redhat:enterprise_linux:6\"]},{\"vendor\":\"Red Hat\",\"product\":\"Red Hat Enterprise Linux 7\",\"defaultStatus\":\"unaffected\",\"collectionURL\":\"https://access.redhat.com/downloads/content/package-browser/\",\"packageName\":\"sssd\",\"cpes\":[\"cpe:/o:redhat:enterprise_linux:7\"]},{\"vendor\":\"Red Hat\",\"product\":\"Red Hat Enterprise Linux 8\",\"defaultStatus\":\"unaffected\",\"collectionURL\":\"https://access.redhat.com/downloads/content/package-browser/\",\"packageName\":\"sssd\",\"cpes\":[\"cpe:/o:redhat:enterprise_linux:8\"]},{\"vendor\":\"Red Hat\",\"product\":\"Red Hat Enterprise Linux 9\",\"defaultStatus\":\"unaffected\",\"collectionURL\":\"https://access.redhat.com/downloads/content/package-browser/\",\"packageName\":\"sssd\",\"cpes\":[\"cpe:/o:redhat:enterprise_linux:9\"]},{\"vendor\":\"Red Hat\",\"product\":\"Red Hat OpenShift Container Platform 4\",\"defaultStatus\":\"unaffected\",\"collectionURL\":\"https://access.redhat.com/downloads/content/package-browser/\",\"packageName\":\"openshift/ose-rhel-coreos-8\",\"cpes\":[\"cpe:/a:redhat:openshift:4\"]},{\"vendor\":\"Red Hat\",\"product\":\"Red Hat OpenShift Container Platform 4\",\"defaultStatus\":\"unaffected\",\"collectionURL\":\"https://access.redhat.com/downloads/content/package-browser/\",\"packageName\":\"openshift/ose-rhel-coreos-9\",\"cpes\":[\"cpe:/a:redhat:openshift:4\"]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"secalert@redhat.com\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H\",\"baseScore\":7.5,\"baseSeverity\":\"HIGH\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"HIGH\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":1.6,\"impactScore\":5.9}],\"ssvcV203\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"ssvcData\":{\"timestamp\":\"2026-09-09T18:28:46.606582Z\",\"id\":\"CVE-2026-87853\",\"options\":[{\"exploitation\":\"none\"},{\"automatable\":\"no\"},{\"technicalImpact\":\"total\"}],\"role\":\"CISA Coordinator\",\"version\":\"2.0.3\"}}]},\"weaknesses\":[{\"source\":\"secalert@redhat.com\",\"type\":\"Secondary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-187\"}]}],\"references\":[{\"url\":\"https://access.redhat.com/security/cve/CVE-2026-87853\",\"source\":\"secalert@redhat.com\"},{\"url\":\"https://bugzilla.redhat.com/show_bug.cgi?id=2530888\",\"source\":\"secalert@redhat.com\"}]}}",
"redhat_vex": {
"aggregate_severity": "Moderate",
"current_release_date": "2026-09-09T16:54:02+00:00",
"cve": "CVE-2026-87853",
"id": "CVE-2026-87853",
"initial_release_date": "2026-09-09T14:15:45.513000+00:00",
"product_status:known_affected": "61",
"product_status:known_not_affected": "105",
"source": "Red Hat CSAF VEX",
"status": "final",
"title": "sssd: sssd: IdP authentication prefix comparison allows cross-user impersonation",
"url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-87853.json",
"version": "3"
},
"vulnrichment": {
"containers": "{\"cna\": {\"title\": \"Sssd: sssd: idp authentication prefix comparison allows cross-user impersonation\", \"metrics\": [{\"other\": {\"content\": {\"value\": \"Moderate\", \"namespace\": \"https://access.redhat.com/security/updates/classification/\"}, \"type\": \"Red Hat severity rating\"}}, {\"cvssV3_1\": {\"attackComplexity\": \"HIGH\", \"attackVector\": \"NETWORK\", \"availabilityImpact\": \"HIGH\", \"baseScore\": 7.5, \"baseSeverity\": \"HIGH\", \"confidentialityImpact\": \"HIGH\", \"integrityImpact\": \"HIGH\", \"privilegesRequired\": \"LOW\", \"scope\": \"UNCHANGED\", \"userInteraction\": \"NONE\", \"vectorString\": \"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H\", \"version\": \"3.1\"}, \"format\": \"CVSS\"}], \"descriptions\": [{\"lang\": \"en\", \"value\": \"A flaw was found in SSSD\u0027s IdP authentication provider. The eval_access_token_buf() function compares the OIDC subject identifier using strncmp() with the authenticated user\u0027s identifier length, performing a prefix comparison instead of an exact match. An attacker whose IdP identifier is a strict prefix of a target user\u0027s identifier can authenticate as the target user.\"}], \"affected\": [{\"vendor\": \"Red Hat\", \"product\": \"Red Hat Enterprise Linux 10\", \"collectionURL\": \"https://access.redhat.com/downloads/content/package-browser/\", \"packageName\": \"sssd\", \"defaultStatus\": \"affected\", \"cpes\": [\"cpe:/o:redhat:enterprise_linux:10\"]}, {\"vendor\": \"Red Hat\", \"product\": \"Red Hat Enterprise Linux 6\", \"collectionURL\": \"https://access.redhat.com/downloads/content/package-browser/\", \"packageName\": \"sssd\", \"defaultStatus\": \"unknown\", \"cpes\": [\"cpe:/o:redhat:enterprise_linux:6\"]}, {\"vendor\": \"Red Hat\", \"product\": \"Red Hat Enterprise Linux 7\", \"collectionURL\": \"https://access.redhat.com/downloads/content/package-browser/\", \"packageName\": \"sssd\", \"defaultStatus\": \"unaffected\", \"cpes\": [\"cpe:/o:redhat:enterprise_linux:7\"]}, {\"vendor\": \"Red Hat\", \"product\": \"Red Hat Enterprise Linux 8\", \"collectionURL\": \"https://access.redhat.com/downloads/content/package-browser/\", \"packageName\": \"sssd\", \"defaultStatus\": \"unaffected\", \"cpes\": [\"cpe:/o:redhat:enterprise_linux:8\"]}, {\"vendor\": \"Red Hat\", \"product\": \"Red Hat Enterprise Linux 9\", \"collectionURL\": \"https://access.redhat.com/downloads/content/package-browser/\", \"packageName\": \"sssd\", \"defaultStatus\": \"unaffected\", \"cpes\": [\"cpe:/o:redhat:enterprise_linux:9\"]}, {\"vendor\": \"Red Hat\", \"product\": \"Red Hat OpenShift Container Platform 4\", \"collectionURL\": \"https://access.redhat.com/downloads/content/package-browser/\", \"packageName\": \"openshift/ose-rhel-coreos-8\", \"defaultStatus\": \"unaffected\", \"cpes\": [\"cpe:/a:redhat:openshift:4\"]}, {\"vendor\": \"Red Hat\", \"product\": \"Red Hat OpenShift Container Platform 4\", \"collectionURL\": \"https://access.redhat.com/downloads/content/package-browser/\", \"packageName\": \"openshift/ose-rhel-coreos-9\", \"defaultStatus\": \"unaffected\", \"cpes\": [\"cpe:/a:redhat:openshift:4\"]}], \"references\": [{\"url\": \"https://access.redhat.com/security/cve/CVE-2026-87853\", \"tags\": [\"vdb-entry\", \"x_refsource_REDHAT\"]}, {\"url\": \"https://bugzilla.redhat.com/show_bug.cgi?id=2530888\", \"name\": \"RHBZ#2530888\", \"tags\": [\"issue-tracking\", \"x_refsource_REDHAT\"]}], \"datePublic\": \"2026-09-09T14:15:45.513Z\", \"problemTypes\": [{\"descriptions\": [{\"cweId\": \"CWE-187\", \"description\": \"Partial String Comparison\", \"lang\": \"en\", \"type\": \"CWE\"}]}], \"x_redhatCweChain\": \"CWE-187: Partial String Comparison\", \"workarounds\": [{\"lang\": \"en\", \"value\": \"Deployments not using the IdP authentication provider (idp_type = keycloak) are not affected. For affected deployments: (1) If using Keycloak LDAP federation, switching to Import Users: enabled mode causes Keycloak to assign random UUIDs as sub claims, making prefix collisions astronomically unlikely. (2) Restrict PAM login to specific users via simple_allow_users or access_provider = simple. (3) Disable Keycloak self-registration to prevent attackers from creating accounts with chosen prefix usernames.\"}], \"timeline\": [{\"lang\": \"en\", \"time\": \"2026-09-06T00:00:00.000Z\", \"value\": \"Reported to Red Hat.\"}, {\"lang\": \"en\", \"time\": \"2026-09-09T14:15:45.513Z\", \"value\": \"Made public.\"}], \"credits\": [{\"lang\": \"en\", \"value\": \"Red Hat would like to thank Moritz Theile for reporting this issue.\"}], \"providerMetadata\": {\"orgId\": \"53f830b8-0a3f-465b-8143-3b8a9948e749\", \"shortName\": \"redhat\", \"dateUpdated\": \"2026-09-09T16:06:25.638Z\"}, \"x_generator\": {\"engine\": \"cvelib 1.8.0\"}}, \"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-87853\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"total\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-09-09T18:28:46.606582Z\"}}}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-09-09T18:28:47.683Z\"}}]}",
"cveMetadata": "{\"cveId\": \"CVE-2026-87853\", \"assignerOrgId\": \"53f830b8-0a3f-465b-8143-3b8a9948e749\", \"state\": \"PUBLISHED\", \"assignerShortName\": \"redhat\", \"dateReserved\": \"2026-09-09T13:00:35.698Z\", \"datePublished\": \"2026-09-09T16:06:25.638Z\", \"dateUpdated\": \"2026-09-10T14:56:49.929Z\"}",
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
Loading…
Loading…
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.
Loading…
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.
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.
Loading…
Loading…