CVE-2026-90996

Summary

A flaw was found in sssd. A local unprivileged user could send a specially crafted request with a zero-length body to the Network Security Services (NSS) responder. This could lead to a denial-of-service condition, causing the NSS responder to become unstable or terminate. This vulnerability affects the availability of the system responder.

Affected Software

Weaknesses

• CWE-191: Integer Underflow (Wrap or Wraparound)

Workarounds

To mitigate this issue, restrict access to the NSS responder UNIX socket or disable the NSS responder if it is not required. The NSS responder can be disabled by editing the /etc/sssd/sssd.conf file and removing nss from the services line in the [sssd] section. After modifying the configuration, restart the SSSD service for the changes to take effect. Disabling the NSS responder may impact local user and group resolution.

Example:

# Remove 'nss' from the services line in /etc/sssd/sssd.conf
# Before: services = nss, pam, autofs
# After: services = pam, autofs

sudo systemctl restart sssd

Warning: Restarting the sssd service will temporarily interrupt authentication and authorization services.

References

• https://access.redhat.com/security/cve/CVE-2026-90996
• https://bugzilla.redhat.com/show_bug.cgi?id=2478986

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