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CVE-2026-87853— Sssd: sssd: idp authentication prefix comparison allows cross-user impersonation

Quick assessment

Affected
Red Hat Red Hat Enterprise Linux 10
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

以下是该漏洞描述的中文翻译： SSSD 的 IdP 身份验证组件中发现一个缺陷。 在 函数中，系统使用 并基于已认证用户标识符的长度来比较 OIDC 主题标识符，执行的是前缀比较而非精确匹配。因此，如果攻击者的 IdP 标识符是目标用户标识符的严格前缀（即目标标识符以攻击者标识符开头且更长），攻击者即可冒充目标用户完成认证。

CVSS 7.5 · High

Possible ATT&CK Techniques 1 AI

T1078.001 · Default Accounts
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I. Basic Information for CVE-2026-87853

Vulnerability Information
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Vulnerability Title
Sssd: sssd: idp authentication prefix comparison allows cross-user impersonation
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
部分比较
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
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
Red Hat Red Hat OpenShift Container Platform 4 - cpe:/a:redhat:openshift:4

II. Public POCs for CVE-2026-87853

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III. Intelligence Information for CVE-2026-87853

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Other References for CVE-2026-87853 (2)

Same Patch Batch · Red Hat · 2026-09-09 · 8 CVEs total

CVE-2026-87766 8.8 HIGH Bubblewrap: bubblewrap: symlink traversal via /oldroot allows writing files outside sandbo
CVE-2026-18147 8.1 HIGH Freeipa: ipa: freeipa/idm: cross-site scripting vulnerability allows arbitrary code execut
CVE-2026-87874 8.1 HIGH Community.general: community.general: memcached cache plugin deserializes untrusted pickle
CVE-2026-87872 6.8 MEDIUM Community.general: community.general: ocapi module_utils (ocapi_command, ocapi_info) hardc
CVE-2026-19729 4.9 MEDIUM Keycloak-services: keycloak-services: incomplete fix for arbitrary filesystem path probing
CVE-2026-87875 4.3 MEDIUM Cups: openprinting cups: heap out-of-bounds read in cupsutf32toutf8() via missing source-l
CVE-2026-87876 3.0 LOW Cups: openprinting cups: remaining case-insensitive username matching in scheduler side pa

IV. Related Vulnerabilities

Same product: Red Hat Enterprise Linux 10
Same vendor: Red Hat
Same weakness: CWE-187

V. Comments for CVE-2026-87853

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