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Vulnerability · Published Sep 9, 2026 · Assigned by redhat

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

High 7.5

In plain English

A high-severity security flaw in Red Hat Enterprise Linux 10 from Red Hat. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 26% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.5High
Exploit odds (30 days)0.3%top 74.0% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
AlmaLinux:10libipa_hbac2.12.0-3.el10_2.2ALSA-2026:77534
AlmaLinux:10libsss_autofs2.12.0-3.el10_2.2ALSA-2026:77534
AlmaLinux:10libsss_certmap2.12.0-3.el10_2.2ALSA-2026:77534
AlmaLinux:10libsss_idmap2.12.0-3.el10_2.2ALSA-2026:77534
AlmaLinux:10libsss_nss_idmap2.12.0-3.el10_2.2ALSA-2026:77534
AlmaLinux:10libsss_nss_idmap-devel2.12.0-3.el10_2.2ALSA-2026:77534
AlmaLinux:10libsss_sudo2.12.0-3.el10_2.2ALSA-2026:77534
AlmaLinux:10python3-libipa_hbac2.12.0-3.el10_2.2ALSA-2026:77534
AlmaLinux:10python3-libsss_nss_idmap2.12.0-3.el10_2.2ALSA-2026:77534
AlmaLinux:10python3-sss2.12.0-3.el10_2.2ALSA-2026:77534
AlmaLinux:10python3-sss-murmur2.12.0-3.el10_2.2ALSA-2026:77534
AlmaLinux:10python3-sssdconfig2.12.0-3.el10_2.2ALSA-2026:77534
AlmaLinux:10sssd2.12.0-3.el10_2.2ALSA-2026:77534
AlmaLinux:10sssd-ad2.12.0-3.el10_2.2ALSA-2026:77534
AlmaLinux:10sssd-client2.12.0-3.el10_2.2ALSA-2026:77534
AlmaLinux:10sssd-common2.12.0-3.el10_2.2ALSA-2026:77534
AlmaLinux:10sssd-common-pac2.12.0-3.el10_2.2ALSA-2026:77534
AlmaLinux:10sssd-dbus2.12.0-3.el10_2.2ALSA-2026:77534
AlmaLinux:10sssd-idp2.12.0-3.el10_2.2ALSA-2026:77534
AlmaLinux:10sssd-ipa2.12.0-3.el10_2.2ALSA-2026:77534
AlmaLinux:10sssd-kcm2.12.0-3.el10_2.2ALSA-2026:77534
AlmaLinux:10sssd-krb52.12.0-3.el10_2.2ALSA-2026:77534
AlmaLinux:10sssd-krb5-common2.12.0-3.el10_2.2ALSA-2026:77534
AlmaLinux:10sssd-ldap2.12.0-3.el10_2.2ALSA-2026:77534
AlmaLinux:10sssd-nfs-idmap2.12.0-3.el10_2.2ALSA-2026:77534
AlmaLinux:10sssd-passkey2.12.0-3.el10_2.2ALSA-2026:77534
AlmaLinux:10sssd-proxy2.12.0-3.el10_2.2ALSA-2026:77534
AlmaLinux:10sssd-tools2.12.0-3.el10_2.2ALSA-2026:77534
AlmaLinux:10sssd-winbind-idmap2.12.0-3.el10_2.2ALSA-2026:77534
Debian:12sssdno fix listedDEBIAN-CVE-2026-87853
Debian:13sssdno fix listedDEBIAN-CVE-2026-87853
Rocky Linux:10sssd0:2.12.0-3.el10_2.2RLSA-2026:77534
Ubuntu:22.04:LTSsssdno fix listedUBUNTU-CVE-2026-87853
Ubuntu:24.04:LTSsssdno fix listedUBUNTU-CVE-2026-87853
Ubuntu:26.04:LTSsssdno fix listedUBUNTU-CVE-2026-87853
Ubuntu:26.10sssdno fix listedUBUNTU-CVE-2026-87853

Affected products (as reported)

VendorProductVersions
Red Hat Red Hat Enterprise Linux 10 see references
Red Hat Red Hat Enterprise Linux 6 see references
Red Hat Red Hat Enterprise Linux 7 see references
Red Hat Red Hat Enterprise Linux 8 see references
Red Hat Red Hat Enterprise Linux 9 see references
Red Hat Red Hat OpenShift Container Platform 4 see references
Red Hat Red Hat OpenShift Container Platform 4 see references
Red Hat Red Hat OpenShift Container Platform 5 see references

Weakness: CWE-187 · Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

References