CVE-2017-2800 : Detail

CVE-2017-2800

9.8
/
Critical
Authorization problems
A07-Identif. and Authent. Fail
13.74%V3
Network
2017-05-24
12h00 +00:00
2022-04-19
16h22 +00:00
CVE.org
NVD
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CVE Descriptions

A specially crafted x509 certificate can cause a single out of bounds byte overwrite in wolfSSL through 3.10.2 resulting in potential certificate validation vulnerabilities, denial of service and possible remote code execution. In order to trigger this vulnerability, the attacker needs to supply a malicious x509 certificate to either a server or a client application using this library.

CVE Informations

Related Weaknesses

CWE-ID Weakness Name Source
CWE-295 Improper Certificate Validation
The product does not validate, or incorrectly validates, a certificate.

Metrics

Metrics Score Severity CVSS Vector Source
V3.1 9.8 CRITICAL CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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.

Network

The vulnerable component 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).

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.

None

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

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.

High

There is a 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.

High

There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to 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]
V3.0 8.1 HIGH CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/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.

Network

A vulnerability exploitable with network access means the vulnerable component is bound to the network stack and the attacker's path is through OSI layer 3 (the network layer). Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable one or more network hops away (e.g. across layer 3 boundaries from routers).

Attack Complexity

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

High

A successful attack depends on conditions beyond the attacker's control. That is, a successful attack cannot be accomplished at will, but requires the attacker to invest in some measurable amount of effort in preparation or execution against the vulnerable component before a successful attack can be expected.

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 to carry out an attack.

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.

High

There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to 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 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 that one has in the description of a vulnerability.

Environmental Metrics
V2 7.5 AV:N/AC:L/Au:N/C:P/I:P/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 : 41984

Publication date : 2017-05-08 22h00 +00:00
Author : Talos
EDB Verified : No

TALOS-2017-0293 WOLFSSL LIBRARY X509 CERTIFICATE TEXT PARSING CODE EXECUTION VULNERABILITY MAY 8, 2017 CVE-2017-2800 SUMMARY An exploitable off-by-one write vulnerability exists in the x509 certificate parsing functionality of wolfSSL library versions up to 3.10.2. A specially crafted x509 certificate can cause a single out of bounds byte overwrite resulting in potential certificate validation vulnerabilities, denial of service and possible remote code execution. In order to trigger this vulnerability, the attacker needs to supply a malicious x509 certificate to either server or client application using this library. TESTED VERSIONS WolfSSL 3.10.2 PRODUCT URLS https://www.wolfssl.com CVSSV3 SCORE 8.1 - CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H CWE CWE-193: Off-by-one Error DETAILS WolfSSL, previously CyaSSL, is a lightweight SSL/TLS library targeted for embedded and RTOS environments, primarily because of its small size, speed, portability, and feature set. According to the vendor it is used in wide range of products including industrial control systems, IoT devices, VoIP hardware, routers and more. The vulnerability exists in x509 code that deals with string fields in DER certificates. Specifically, when parsing commonName, countryName, localityName, stateName, orgName or orgUnit fields, the function wolfSSL_X509_NAME_get_text_by_NID is used. Its prototype is: int wolfSSL_X509_NAME_get_text_by_NID(WOLFSSL_X509_NAME* name, int nid, char* buf, int len); Its task is to copy the appropriate string from name context into supplied buf of length len. The issue happens when the string is longer or equal to length of the allocated buffer. Following code highlights the issue for the case of commonName field: int wolfSSL_X509_NAME_get_text_by_NID(WOLFSSL_X509_NAME* name, int nid, char* buf, int len) { char *text = NULL; int textSz = 0; WOLFSSL_ENTER("wolfSSL_X509_NAME_get_text_by_NID"); switch (nid) { case ASN_COMMON_NAME: text = name->fullName.fullName + name->fullName.cnIdx; [1] textSz = name->fullName.cnLen; [2] break; ... if (buf != NULL && text != NULL) { textSz = min(textSz, len); [3] XMEMCPY(buf, text, textSz); [4] buf[textSz] = '\0'; [5] } At [1] and [2], text and textSz are initialized. At [3] the lesser of the two values textSz and len is chosen. This value ends up as the size parameter to a memcpy call at [4]. Then, the same value is used as an index to NULL terminate the string at [5]. If the string length is bigger than size of the allocated buffer, NULL termination at index textSz will cause an off-by-one NULL byte write into adjacent memory variable on the stack or heap, depending on where the buffer was allocated. Depending on the way the library is used, this could lead to further issues when doing certificate validation or potentially result in remote code execution. The vulnerability can be triggered by supplying the attached PoC x509 certificate to the certfileds example app from wolfssl-examples. CRASH INFORMATION Address sanitizer output: ==97602==ERROR: AddressSanitizer: stack-buffer-overflow on address 0x7fffffffe1a0 at pc 0x7ffff7b73f56 bp 0x7fffffff8410 sp 0x7fffffff8408 WRITE of size 1 at 0x7fffffffe1a0 thread T0 #0 0x7ffff7b73f55 in wolfSSL_X509_NAME_get_text_by_NID wolfssl/src/ssl.c:12458 #1 0x7ffff7b73f55 in ?? ??:0 #2 0x4ea99d in main wolfssl/wolfssl-examples/certfields/main.c:128 #3 0x4ea99d in ?? ??:0 #4 0x7ffff6afe82f in __libc_start_main /build/glibc-Qz8a69/glibc-2.23/csu/../csu/libc-start.c:291 #5 0x7ffff6afe82f in ?? ??:0 #6 0x418c48 in _start ??:? #7 0x418c48 in ?? ??:0 Address 0x7fffffffe1a0 is located in stack of thread T0 at offset 23872 in frame #0 0x4ea2af in main wolfssl/wolfssl-examples/certfields/main.c:44 #1 0x4ea2af in ?? ??:0 This frame has 10 object(s): [32, 14128) 'derCert' [14384, 14388) 'idx' [14400, 23280) 'pubKey' [23536, 23544) 'cert' [23568, 23648) 'commonName' [23680, 23760) 'countryName' [23792, 23872) 'localityName' <== Memory access at offset 23872 overflows this variable [23904, 23984) 'stateName' [24016, 24096) 'orgName' [24128, 24208) 'orgUnit' HINT: this may be a false positive if your program uses some custom stack unwind mechanism or swapcontext (longjmp and C++ exceptions *are* supported) SUMMARY: AddressSanitizer: stack-buffer-overflow (/usr/local/lib/libwolfssl.so.3+0x184f55) Shadow bytes around the buggy address: 0x10007fff7be0: 00 00 00 00 00 00 00 00 00 00 f2 f2 f2 f2 f2 f2 0x10007fff7bf0: f2 f2 f2 f2 f2 f2 f2 f2 f2 f2 f2 f2 f2 f2 f2 f2 0x10007fff7c00: f2 f2 f2 f2 f2 f2 f2 f2 f2 f2 00 f2 f2 f2 00 00 0x10007fff7c10: 00 00 00 00 00 00 00 00 f2 f2 f2 f2 00 00 00 00 0x10007fff7c20: 00 00 00 00 00 00 f2 f2 f2 f2 00 00 00 00 00 00 =>0x10007fff7c30: 00 00 00 00[f2]f2 f2 f2 00 00 00 00 00 00 00 00 0x10007fff7c40: 00 00 f2 f2 f2 f2 00 00 00 00 00 00 00 00 00 00 0x10007fff7c50: f2 f2 f2 f2 00 00 00 00 00 00 00 00 00 00 f3 f3 0x10007fff7c60: f3 f3 f3 f3 00 00 00 00 00 00 00 00 00 00 00 00 0x10007fff7c70: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x10007fff7c80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 Shadow byte legend (one shadow byte represents 8 application bytes): Addressable: 00 Partially addressable: 01 02 03 04 05 06 07 Heap left redzone: fa Heap right redzone: fb Freed heap region: fd Stack left redzone: f1 Stack mid redzone: f2 Stack right redzone: f3 Stack partial redzone: f4 Stack after return: f5 Stack use after scope: f8 Global redzone: f9 Global init order: f6 Poisoned by user: f7 Container overflow: fc Array cookie: ac Intra object redzone: bb ASan internal: fe Left alloca redzone: ca Right alloca redzone: cb ==97602==ABORTING EXPLOIT PROOF-OF-CONCEPT A certificate that triggers this vulnerability can be generated using the following openssl command: openssl req -x509 -newkey rsa:4096 -keyout key.pem -out cert1.pem -days 365 -subj "/C=US/ST=Maryland/L=AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA/O=E/CN=A" CREDIT Discovered by Aleksandar Nikolic of Cisco Talos. TIMELINE 2017-03-14 - Vendor Disclosure 2017-05-04 - Public Release

Products Mentioned

Configuraton 0

Wolfssl>>Wolfssl >> Version To (including) 3.10.2

References

https://www.exploit-db.com/exploits/41984/
Tags : exploit, x_refsource_EXPLOIT-DB