Coordinated Disclosure Timeline
- 2021-08-31: Created an issue to ask for contact details.
- 2021-08-31: Burak Arslan (burak.arslan@arskom.com.tr) got in touch to ask for more details. I have now emailed the report to Burak.
- 2021-10-14: Emailed my suggested fix to Burak Arslan.
- 2021-10-18: Reply from Burak Arslan, who says it’s ok to create a pull request.
- 2021-10-18: Created https://github.com/arskom/spyne/pull/675
- 2021-10-18: Fix is merged.
Summary
Spyne contains a regular expression that is vulnerable to ReDoS (Regular Expression Denial of Service).
Product
Spyne
Tested Version
Details
ReDoS
ReDoS, or Regular Expression Denial of Service, is a vulnerability affecting inefficient regular expressions which can perform extremely badly when run on a crafted input string.
This vulnerability was found using a CodeQL query which identifies inefficient regular expressions. You can see the results of the query on Spyne by following this link.
Vulnerability
The vulnerable regular expression is here.
To see that the regular expression is vulnerable, copy-paste it into a separate file as shown below:
- Run the code below with
python3:
import re
email_re = re.compile(
r"[A-Za-z0-9!#-'\*\+\-/=\?\^_`\{-~]+"
r"(\.[A-Za-z0-9!#-'\*\+\-/=\?\^_`\{-~]+)*@"
# domain part is either a single symbol
r"(([a-zA-Z0-9]|"
# or have at least two symbols
# hyphen can't be at the beginning or end of domain part
# domain should contain at least 2 parts, the last one is TLD
r"([a-zA-Z0-9][a-zA-Z0-9\-]*[a-zA-Z0-9])+)\.)+"
# TLD should contain only letters, at least 2
r"[A-Za-z]{2,}", re.IGNORECASE)
print(email_re.match("~.~@a0" + "0000" * 25))
Impact
This issue may lead to a denial of service.
Credit
This issue was discovered by GitHub team members @erik-krogh (Erik Krogh Kristensen) and @yoff (Rasmus Petersen).
Contact
You can contact the GHSL team at securitylab@github.com, please include a reference to GHSL-2021-115 in any communication regarding this issue.