7.5

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

Awaiting analysis
AliasesRHSA-2026:77534UBUNTU-CVE-2026-87853DEBIAN-CVE-2026-87853
Published 09-09-2026Last modified 03-11-2026

Vulnerability summary

CVE-2026-87853 is a high (CVSS 7.5) Partial String Comparison vulnerability in sssd. EPSS estimates a 0.33% chance of exploitation in the next 30 days, higher than 25.9% of scored vulnerabilities.

Priority
Routine

Not severe (CVSS 7.5, network access); no exploitation reported by the 5 checked sources

Source freshness unavailable

How is this decided?
CVSS score
7.5/10
010
High · v3.1 (CVE.org)
EPSS score
0.33%
0%100%
Low · -0.15 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Timeline

  1. 09-09-2026
    PublishedVulnerability first disclosed.
  2. 03-11-2026
    Last modifiedVulnerability information updated.

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.

CVSS metrics

5 scores · 5 sources · 1 version

EPSS trend

Probability

0.33%

Chance of exploitation in the next 30 days

Percentile

26%

Versus all other CVEs

30-day change

Decrease -0.15 pp

From 0.48% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: network-reachable, low-privilege account, no user interaction (CVSS vector). Other conditions: not stated in public data.

Redhat57 products
  • libipa_hbac< 0:2.12.0-3.el10_2.2
  • libipa_hbac-debuginfo< 0:2.12.0-3.el10_2.2
  • libsss_autofs< 0:2.12.0-3.el10_2.2
  • libsss_autofs-debuginfo< 0:2.12.0-3.el10_2.2
  • libsss_certmap< 0:2.12.0-3.el10_2.2
Debian1 product
  • sssdAll versions (No fix recorded)
Opensuse1 product
  • sssd&distro=openSUSE Tumbleweed< 2.13.1-3.1
Ubuntu1 product
  • sssdAll versions (No fix recorded)

4 vendors · 60 products

References

10 links