CVE-2026-87853: Partial String Comparison in Red Hat Red Hat Enterprise Linux 10
Affects Red Hat Red Hat Enterprise Linux 10Source CVE Database V5
Not known to be exploited · CVSS 7.5 High : monitor for a fix to Red Hat Red Hat Enterprise Linux 10.
Data as of 10/24/2026, 20:40:32 UTC
- Exploitation
Not in CISA KEV, no exploitation reported
- EPSS
- 0.3% chance of exploitation in 30 days – higher than 24% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:HWhat to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| Red HatRed Hat Enterprise Linux 10 | Affected– | Fixed in– |
| Red HatRed Hat Enterprise Linux 6 | Affected– | Fixed in– |
| Red HatRed Hat Enterprise Linux 7 | Affected– | Fixed in– |
| Red HatRed Hat Enterprise Linux 8 | Affected– | Fixed in– |
| Red HatRed Hat Enterprise Linux 9 | Affected– | Fixed in– |
| Red HatRed Hat OpenShift Container Platform 4 | Affected– | Fixed in– |
AI-suggested
Red Hat has released an official security update for SSSD that fixes this vulnerability. Users of Red Hat Enterprise Linux 10 should apply the update as described in Red Hat advisory RHSA-2026:77534 and the referenced article https://access.redhat.com/articles/11258. Applying this update mitigates the vulnerability.
Description
CVE-2026-87853 is a vulnerability in the System Security Services Daemon (SSSD) of Red Hat Enterprise Linux 10. The flaw occurs in the IdP authentication provider where a partial string comparison is performed using strncmp(), allowing an attacker whose IdP identifier is a strict prefix of a target user's identifier to impersonate that user. This issue has a CVSS score of 7.5 and is rated as high severity. Red Hat has released an update to fix this vulnerability in SSSD.
Impact
An attacker can impersonate another user if their IdP identifier is a strict prefix of the target user's identifier, potentially gaining unauthorized access and privileges. This leads to confidentiality, integrity, and availability impacts as indicated by the CVSS vector (C:H/I:H/A:H).
Summary
The vulnerability exists in the eval_access_token_buf() function of SSSD's IdP authentication provider in Red Hat Enterprise Linux 10. The function compares the OIDC subject identifier using strncmp() with the length of the authenticated user's identifier, resulting in a prefix comparison rather than an exact match. This allows an attacker with an IdP identifier that is a strict prefix of another user's identifier to authenticate as that user, leading to cross-user impersonation. Red Hat has issued a security advisory and released patches addressing this issue.