Headline
CVE-2022-25844: Regular Expression Denial of Service (ReDoS) in org.webjars.npm:angular | CVE-2022-25844 | Snyk
The package angular after 1.7.0 are vulnerable to Regular Expression Denial of Service (ReDoS) by providing a custom locale rule that makes it possible to assign the parameter in posPre: ' '.repeat() of NUMBER_FORMATS.PATTERNS[1].posPre with a very high value. Note: 1) This package has been deprecated and is no longer maintained. 2) The vulnerable versions are 1.7.0 and higher.
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren’t very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
- A The string must start with the letter ‘A’
- (B|C+)+ The string must then follow the letter A with either the letter ‘B’ or some number of occurrences of the letter ‘C’ (the + matches one or more times). The + at the end of this section states that we can look for one or more matches of this section.
- D Finally, we ensure this section of the string ends with a ‘D’
The expression would match inputs such as ABBD, ABCCCCD, ABCBCCCD and ACCCCCD
It most cases, it doesn’t take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let’s look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C’s:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn’t match.
From there, the number of steps the engine must use to validate a string just continues to grow.
String
Number of C’s
Number of steps
ACCCX
3
38
ACCCCX
4
71
ACCCCCX
5
136
ACCCCCCCCCCCCCCX
14
65,553
By the time the string includes 14 C’s, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Related news
The RSS extension before 2022-04-29 for MediaWiki allows XSS via an rss element (if the feed is in $wgRSSUrlWhitelist and $wgRSSAllowLinkTag is true).
In Progress OpenEdge before 11.7.14 and 12.x before 12.2.9, certain SUID binaries within the OpenEdge application were susceptible to privilege escalation. If exploited, a local attacker could elevate their privileges and compromise the affected system.
nopCommerce 4.50.1 is vulnerable to Directory Traversal via the backup file in the Maintenance feature.
Cyclos 4 PRO 4.14.7 and before does not validate user input at error inform, which allows remote unauthenticated attacker to execute javascript code via undefine enum constant.
A Dom-based Cross-site scripting (XSS) vulnerability at registration account in Cyclos 4 PRO.14.7 and before allows remote attackers to inject arbitrary web script or HTML via the groupId parameter.
All versions of package jsgui-lang-essentials are vulnerable to Prototype Pollution due to allowing all Object attributes to be altered, including their magical attributes such as proto, constructor and prototype.
All versions of package com.bstek.ureport:ureport2-console are vulnerable to Remote Code Execution by connecting to a malicious database server, causing arbitrary file read and deserialization of local gadgets.
All versions of package masuit.tools.core are vulnerable to Arbitrary Code Execution via the ReceiveVarData<T> function in the SocketClient.cs component. The socket client in the package can pass in the payload via the user-controllable input after it has been established, because this socket client transmission does not have the appropriate restrictions or type bindings for the BinaryFormatter.
All versions of package jailed are vulnerable to Sandbox Bypass via an exported alert() method which can access the main application. Exported methods are stored in the application.remote object.
All versions of package materialize-css are vulnerable to Cross-site Scripting (XSS) due to improper escape of user input (such as <not-a-tag />) that is being parsed as HTML/JavaScript, and inserted into the Document Object Model (DOM). This vulnerability can be exploited when the user-input is provided to the autocomplete component.
All versions of package com.alibaba.oneagent:one-java-agent-plugin are vulnerable to Arbitrary File Write via Archive Extraction (Zip Slip) using a specially crafted archive that holds directory traversal filenames (e.g. ../../evil.exe). The attacker can overwrite executable files and either invoke them remotely or wait for the system or user to call them, thus achieving remote command execution on the victim’s machine.
The package git-pull-or-clone before 2.0.2 are vulnerable to Command Injection due to the use of the --upload-pack feature of git which is also supported for git clone. The source includes the use of the secure child process API spawn(). However, the outpath parameter passed to it may be a command-line argument to the git clone command and result in arbitrary command injection.
The package com.google.code.gson:gson before 2.8.9 are vulnerable to Deserialization of Untrusted Data via the writeReplace() method in internal classes, which may lead to DoS attacks.
All versions of package dset are vulnerable to Prototype Pollution via 'dset/merge' mode, as the dset function checks for prototype pollution by validating if the top-level path contains __proto__, constructor or protorype. By crafting a malicious object, it is possible to bypass this check and achieve prototype pollution.
The package s-cart/s-cart before 6.9; the package s-cart/core before 6.9 are vulnerable to Cross-site Scripting (XSS) which can lead to cookie stealing of any victim that visits the affected URL so the attacker can gain unauthorized access to that user's account through the stolen cookie.
This affects all versions of package libxmljs. When invoking the libxmljs.parseXml function with a non-buffer argument the V8 code will attempt invoking the .toString method of the argument. If the argument's toString value is not a Function object V8 will crash.
The package dexie before 3.2.2, from 4.0.0-alpha.1 and before 4.0.0-alpha.3 are vulnerable to Prototype Pollution in the Dexie.setByKeyPath(obj, keyPath, value) function which does not properly check the keys being set (like __proto__ or constructor). This can allow an attacker to add/modify properties of the Object.prototype leading to prototype pollution vulnerability. **Note:** This vulnerability can occur in multiple ways, for example when modifying a collection with untrusted user input.
The package sqlite3 before 5.0.3 are vulnerable to Denial of Service (DoS) which will invoke the toString function of the passed parameter. If passed an invalid Function object it will throw and crash the V8 engine.
The package convict before 6.2.2 are vulnerable to Prototype Pollution via the convict function due to missing validation of parentKey. **Note:** This vulnerability derives from an incomplete fix of another [vulnerability](https://security.snyk.io/vuln/SNYK-JS-CONVICT-1062508)