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Re: Regular Expression Denial of Service

Alex Roichman wrote:
Checkmarx Research Lab presents a new attack vector on Web applications. By
exploiting the Regular Expression Denial of Service (ReDoS) vulnerability an
attacker can make a Web application unavailable to its intended users. ReDoS
is commonly known as a “bug” in systems, but Alex Roichman and Adar Weidman
from Checkmarx show how serious it is and how using this technique, various
applications can be “ReDoSed”. These include, among others, Server-side of
Web applications and Client-side Browsers. The art of attacking the Web by
ReDoS is by finding inputs which cannot be matched by Regexes and on these
Regexes a Regex-based Web systems get stuck.

For further reading:

Alex, nice work. Thank you for sharing it with us.

I'd recommend taking a look at Ilja van Sprundel's work with regular expression bugs in his Unusual bugs presentation. ... Where he played a bit with Google Code Search back in 2007, I think. He helped Google out by giving them his research, of course.

I found two versions online:

Ilja and I later discussed creating a real regex fuzzer to discover vulnerabilities, but I at least never had the time to play with it. He might have, I am CC:ing him.

My best to Adar,

Gadi Evron,