The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers). An example of a network attack is an attacker causing a denial of service by sending a specially crafted TCP packet across a wide area network (e.g., CVE-2004-0230).
Attack Complexity
Low
AC
The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Privileges Required
None
PR
The attacker is unauthenticated prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
Scope
Unchanged
S
An exploited vulnerability can only affect resources managed by the same security authority. In the case of a vulnerability in a virtualized environment, an exploited vulnerability in one guest instance would not affect neighboring guest instances.
Confidentiality
High
C
There is total information disclosure, resulting in all data on the system being revealed to the attacker, or there is a possibility of the attacker gaining control over confidential data.
Integrity
None
I
There is no impact on the integrity of the system; the attacker does not gain the ability to modify any files or information on the target system.
Availability
None
A
There is no impact on the availability of the system; the attacker does not have the ability to disrupt access to or use of the system.
Below is a copy: Linux Kernel via Bluetooth Info Leak
Hello,
We are writing to disclose an information leak vulnerability in the
Bluetooth stack of the Linux Kernel (BlueZ).
This vulnerability has been disclosed to the Kernel's security team (
security () kernel org), and a patch for it is in stages of review.
This patch is also attached here.
This 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).
A simple patch for avoiding this info leak is attached.
Prevent stack info leak from the EFS element.
Signed-off-by: Ben Seri <[email protected]>
diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index 43ba91c..fc6615d 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -3363,9 +3363,10 @@ static int l2cap_parse_conf_req(struct l2cap_chan *chan, void *data, size_t data
break;
case L2CAP_CONF_EFS:
-remote_efs = 1;
-if (olen == sizeof(efs))
+if (olen == sizeof(efs)) {
+remote_efs = 1;
memcpy(&efs, (void *) val, olen);
+}
break;
case L2CAP_CONF_EWS:
@@ -3584,16 +3585,17 @@ static int l2cap_parse_conf_rsp(struct l2cap_chan *chan, void *rsp, int len,
break;
case L2CAP_CONF_EFS:
-if (olen == sizeof(efs))
+if (olen == sizeof(efs)) {
memcpy(&efs, (void *)val, olen);
-if (chan->local_stype != L2CAP_SERV_NOTRAFIC &&
- efs.stype != L2CAP_SERV_NOTRAFIC &&
- efs.stype != chan->local_stype)
-return -ECONNREFUSED;
+if (chan->local_stype != L2CAP_SERV_NOTRAFIC &&
+ efs.stype != L2CAP_SERV_NOTRAFIC &&
+ efs.stype != chan->local_stype)
+return -ECONNREFUSED;
-l2cap_add_conf_opt(&ptr, L2CAP_CONF_EFS, sizeof(efs),
- (unsigned long) &efs, endptr - ptr);
+l2cap_add_conf_opt(&ptr, L2CAP_CONF_EFS, sizeof(efs),
+ (unsigned long) &efs, endptr - ptr);
+}
break;
case L2CAP_CONF_FCS:
Ben Seri,
Armis
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