CVE-2026-68743
Description
A flaw was found in SSSD. The extract_authtok_v1() function in the PAM responder does not validate the auth_token_length field against the remaining buffer size before processing. A local attacker can exploit this via a crafted protocol v1 request to the PAM responder socket, causing an out-of-bounds read and process crash, resulting in a denial of service.
Statement
This issue can only be triggered by a local attacker who can connect to the SSSD PAM responder unix socket and send crafted protocol v1 requests. The stock PAM client uses protocol v3 and is not affected by this path. On SSSD 2.10 and later, responders run as an unprivileged user; on earlier versions they may run as root. In either case, the impact is a denial of service of SSSD-mediated authentication. The sssd monitor may respawn the responder, but repeated crashes can lead to a persistent authentication outage for SSSD-managed users. This issue is distinct from CVE-2026-6245, which affects a different code path (pam_passkey_child_read_data).
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Memory
An attacker could get secret values such as cryptographic keys, PII, memory addresses, or other information that could be used in additional attacks.
Confidentiality
Technical Impact: Bypass Protection Mechanism
Out-of-bounds memory could contain memory addresses or other information that can be used to bypass ASLR and other protection mechanisms in order to improve the reliability of exploiting a separate weakness for code execution.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
An attacker could cause a segmentation fault or crash by causing memory to be read outside of the bounds of the buffer. This is especially likely when the code reads a variable amount of data and assumes that a sentinel exists to stop the read operation, such as a NUL in a string.
Other
Technical Impact: Varies by Context
The read operation could produce other undefined or unexpected results.
Acknowledgements
Red Hat would like to thank Vivek Parikh (BreachX Zero Day Labs) for reporting this issue.
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