Vulnerabilities > CVE-2018-19837 - Resource Exhaustion vulnerability in Sass-Lang Libsass
Attack vector
NETWORK Attack complexity
MEDIUM Privileges required
NONE Confidentiality impact
NONE Integrity impact
NONE Availability impact
PARTIAL Summary
In LibSass prior to 3.5.5, Sass::Eval::operator()(Sass::Binary_Expression*) inside eval.cpp allows attackers to cause a denial-of-service resulting from stack consumption via a crafted sass file, because of certain incorrect parsing of '%' as a modulo operator in parser.cpp.
Vulnerable Configurations
Common Weakness Enumeration (CWE)
Common Attack Pattern Enumeration and Classification (CAPEC)
- XML Ping of the Death An attacker initiates a resource depletion attack where a large number of small XML messages are delivered at a sufficiently rapid rate to cause a denial of service or crash of the target. Transactions such as repetitive SOAP transactions can deplete resources faster than a simple flooding attack because of the additional resources used by the SOAP protocol and the resources necessary to process SOAP messages. The transactions used are immaterial as long as they cause resource utilization on the target. In other words, this is a normal flooding attack augmented by using messages that will require extra processing on the target.
- XML Entity Expansion An attacker submits an XML document to a target application where the XML document uses nested entity expansion to produce an excessively large output XML. XML allows the definition of macro-like structures that can be used to simplify the creation of complex structures. However, this capability can be abused to create excessive demands on a processor's CPU and memory. A small number of nested expansions can result in an exponential growth in demands on memory.
- Inducing Account Lockout An attacker leverages the security functionality of the system aimed at thwarting potential attacks to launch a denial of service attack against a legitimate system user. Many systems, for instance, implement a password throttling mechanism that locks an account after a certain number of incorrect log in attempts. An attacker can leverage this throttling mechanism to lock a legitimate user out of their own account. The weakness that is being leveraged by an attacker is the very security feature that has been put in place to counteract attacks.
- Violating Implicit Assumptions Regarding XML Content (aka XML Denial of Service (XDoS)) XML Denial of Service (XDoS) can be applied to any technology that utilizes XML data. This is, of course, most distributed systems technology including Java, .Net, databases, and so on. XDoS is most closely associated with web services, SOAP, and Rest, because remote service requesters can post malicious XML payloads to the service provider designed to exhaust the service provider's memory, CPU, and/or disk space. The main weakness in XDoS is that the service provider generally must inspect, parse, and validate the XML messages to determine routing, workflow, security considerations, and so on. It is exactly these inspection, parsing, and validation routines that XDoS targets. There are three primary attack vectors that XDoS can navigate Target CPU through recursion: attacker creates a recursive payload and sends to service provider Target memory through jumbo payloads: service provider uses DOM to parse XML. DOM creates in memory representation of XML document, but when document is very large (for example, north of 1 Gb) service provider host may exhaust memory trying to build memory objects. XML Ping of death: attack service provider with numerous small files that clog the system. All of the above attacks exploit the loosely coupled nature of web services, where the service provider has little to no control over the service requester and any messages the service requester sends.
Nessus
| NASL family | SuSE Local Security Checks |
| NASL id | OPENSUSE-2019-1791.NASL |
| description | This update for libsass to version 3.6.1 fixes the following issues : Security issues fixed : - CVE-2019-6283: Fixed heap-buffer-overflow in Sass::Prelexer::parenthese_scope(char const*) (boo#1121943). - CVE-2019-6284: Fixed heap-based buffer over-read exists in Sass:Prelexer:alternatives (boo#1121944). - CVE-2019-6286: Fixed heap-based buffer over-read exists in Sass:Prelexer:skip_over_scopes (boo#1121945). - CVE-2018-11499: Fixed use-after-free vulnerability in sass_context.cpp:handle_error (boo#1096894). - CVE-2018-19797: Disallowed parent selector in selector_fns arguments (boo#1118301). - CVE-2018-19827: Fixed use-after-free vulnerability exists in the SharedPtr class (boo#1118346). - CVE-2018-19837: Fixed stack overflow in Eval::operator() (boo#1118348). - CVE-2018-19838: Fixed stack-overflow at IMPLEMENT_AST_OPERATORS expansion (boo#1118349). - CVE-2018-19839: Fixed buffer-overflow (OOB read) against some invalid input (boo#1118351). - CVE-2018-20190: Fixed NULL pointer dereference in Sass::Eval::operator()(Sass::Supports_Operator*) (boo#1119789). - CVE-2018-20821: Fixed uncontrolled recursion in Sass:Parser:parse_css_variable_value (boo#1133200). - CVE-2018-20822: Fixed stack-overflow at Sass::Inspect::operator() (boo#1133201). |
| last seen | 2020-06-01 |
| modified | 2020-06-02 |
| plugin id | 126975 |
| published | 2019-07-24 |
| reporter | This script is Copyright (C) 2019-2020 and is owned by Tenable, Inc. or an Affiliate thereof. |
| source | https://www.tenable.com/plugins/nessus/126975 |
| title | openSUSE Security Update : libsass (openSUSE-2019-1791) |
| code | |
References
- http://lists.opensuse.org/opensuse-security-announce/2019-07/msg00047.html
- http://lists.opensuse.org/opensuse-security-announce/2019-07/msg00051.html
- http://lists.opensuse.org/opensuse-security-announce/2019-08/msg00027.html
- https://github.com/sass/libsass/commit/210fdff7a65370c2ae24e022a2b35da8c423cc5f
- https://github.com/sass/libsass/issues/2659