CVE-2017-1000410 Information

Description

The Linux kernel version 3.3-rc1 and later is affected by a vulnerability lies in the processing of incoming L2CAP commands - ConfigRequest and ConfigResponse messages. This info leak is a result of uninitialized stack variables that may be returned to an attacker in their uninitialized state. By manipulating the code flows that precede the handling of these configuration messages an attacker can also gain some control over which data will be held in the uninitialized stack variables. This can allow him to bypass KASLR and stack canaries protection - as both pointers and stack canaries may be leaked in this manner. Combining this vulnerability (for example) with the previously disclosed RCE vulnerability in L2CAP configuration parsing (CVE-2017-1000251) may allow an attacker to exploit the RCE against kernels which were built with the above mitigations. These are the specifics of this vulnerability: In the function l2cap_parse_conf_rsp and in the function l2cap_parse_conf_req the following variable is declared without initialization: struct l2cap_conf_efs efs; In addition when parsing input configuration parameters in both of these functions the switch case for handling EFS elements may skip the memcpy call that will write to the efs variable: … case L2CAP_CONF_EFS: if (olen == sizeof(efs)) memcpy(&efs (void *)val olen); … The olen in the above if is attacker controlled and regardless of that if in both of these functions the efs variable would eventually be added to the outgoing configuration request that is being built: l2cap_add_conf_opt(&ptr L2CAP_CONF_EFS sizeof(efs) (unsigned long) &efs); So by sending a configuration request or response that contains an L2CAP_CONF_EFS element but with an element length that is not sizeof(efs) - the memcpy to the uninitialized efs variable can be avoided and the uninitialized variable would be returned to the attacker (16 bytes).

CVSS Vector

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Reference

http://seclists.org/oss-sec/2017/q4/357 http://www.securityfocus.com/bid/102101 https://access.redhat.com/errata/RHSA-2018:0654 https://access.redhat.com/errata/RHSA-2018:0676 https://access.redhat.com/errata/RHSA-2018:1062 https://access.redhat.com/errata/RHSA-2018:1130 https://access.redhat.com/errata/RHSA-2018:1170 https://access.redhat.com/errata/RHSA-2018:1319 https://help.ecostruxureit.com/display/public/UADCE725/Security+fixes+in+StruxureWare+Data+Center+Expert+v7.6.0 https://usn.ubuntu.com/3933-1/ https://usn.ubuntu.com/3933-2/ https://www.debian.org/security/2017/dsa-4073 https://www.debian.org/security/2018/dsa-4082

Attack Complexity

LOW

Privileges Required

NONE

User Interaction Required

NONE

Scope

NONE

Confidentiality Impact

UNCHANGED

Integrity Impact

HIGH

Availability Impact

NONE

Base Score

NONE

Base Severity

7.5