Regular Expression Denial of Service (ReDoS)
Detailed paths
Overview
moment is a lightweight JavaScript date library for parsing, validating, manipulating, and formatting dates.
Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) via the preprocessRFC2822() function in from-string.js, when processing a very long crafted string (over 10k characters).
PoC:
moment("(".repeat(500000))
Details
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:
AThe 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.DFinally, 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
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 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.
Remediation
Upgrade moment to version 2.29.4 or higher.
References
Information Exposure
Detailed paths
Overview
node-fetch is a light-weight module that brings window.fetch to node.js
Affected versions of this package are vulnerable to Information Exposure when fetching a remote url with Cookie, if it get a Location response header, it will follow that url and try to fetch that url with provided cookie. This can lead to forwarding secure headers to 3th party.
Remediation
Upgrade node-fetch to version 2.6.7, 3.1.1 or higher.
References
Denial of Service
Detailed paths
Overview
node-fetch is a light-weight module that brings window.fetch to node.js
Affected versions of this package are vulnerable to Denial of Service. Node Fetch did not honor the size option after following a redirect, which means that when a content size was over the limit, a FetchError would never get thrown and the process would end without failure.
Remediation
Upgrade node-fetch to version 2.6.1, 3.0.0-beta.9 or higher.
References
Improper Input Validation
Detailed paths
Overview
go.mongodb.org/mongo-driver/bson/bsonrw is a The MongoDB supported driver for Go.
Affected versions of this package are vulnerable to Improper Input Validation. Specific cstrings input may not be properly validated in the MongoDB Go Driver when marshalling Go objects into BSON. A malicious user could use a Go object with specific string to potentially inject additional fields into marshalled documents.
Remediation
Upgrade go.mongodb.org/mongo-driver/bson/bsonrw to version 1.5.1 or higher.
References
Denial of Service (DoS)
Detailed paths
Overview
Affected versions of this package are vulnerable to Denial of Service (DoS) when handling requests with non-standard HTTP methods.
Note: In order to be affected, an instrumented software must:
use
promhttp.InstrumentHandler*middleware exceptRequestsInFlightnot filter any specific methods (e.g GET) before middleware
pass metric with
methodlabel name to the middlewarenot have any firewall/LB/proxy that filters away requests with unknown
method.
Workarounds:
removing the
methodlabel name fromcounter/gaugeused in theInstrumentHandlerturning off affected
promhttphandlersadding custom middleware before
promhttphandler that will sanitize the request method given by Gohttp.Requestusing a reverse proxy or web application firewall, configured to only allow a limited set of methods.
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its intended and legitimate users.
Unlike other vulnerabilities, DoS attacks usually do not aim at breaching security. Rather, they are focused on making websites and services unavailable to genuine users resulting in downtime.
One popular Denial of Service vulnerability is DDoS (a Distributed Denial of Service), an attack that attempts to clog network pipes to the system by generating a large volume of traffic from many machines.
When it comes to open source libraries, DoS vulnerabilities allow attackers to trigger such a crash or crippling of the service by using a flaw either in the application code or from the use of open source libraries.
Two common types of DoS vulnerabilities:
High CPU/Memory Consumption- An attacker sending crafted requests that could cause the system to take a disproportionate amount of time to process. For example, commons-fileupload:commons-fileupload.
Crash - An attacker sending crafted requests that could cause the system to crash. For Example, npm
wspackage
Remediation
Upgrade github.com/prometheus/client_golang/prometheus/promhttp to version 1.11.1 or higher.
References
Insecure Randomness
Detailed paths
Overview
github.com/masterminds/goutils is a provides users with utility functions to manipulate strings in various ways.
Affected versions of this package are vulnerable to Insecure Randomness via the RandomAlphaNumeric(int) and CryptoRandomAlphaNumeric(int) functions. Small values of int in the functions above will return a smaller subset of results than they should. For example, RandomAlphaNumeric(1) would always return a digit in the 0-9 range, while RandomAlphaNumeric(4) return around ~7 million of the ~13M possible permutations.
Remediation
Upgrade github.com/masterminds/goutils to version 1.1.1 or higher.