Medium [CVE-2026-68743] PAM responder out-of-bounds read via unchecked auth_token_length in protocol v1
This medium-severity Red Hat Linux advisory covers CVE-2026-68743 affecting Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7.
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Summary
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. 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). Red Hat severity: Moderate — CVSS 5.5 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H).
Weakness: CWE-125. Affected Red Hat products: Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 6; Red Hat Enterprise Linux 7; Red Hat Enterprise Linux 8; Red Hat Enterprise Linux 9; Red Hat OpenShift Container Platform 4.
Will not fix / out of support: Red Hat Enterprise Linux 6.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 26 days ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 26 days ago·verify at source
Mitigation checklist
- 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.
Official advisory · high-confidence parse· fetched 26 days ago·verify at source
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