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GHSA-72qw-p7hh-m3ff
No affected components available
Summary
The torbot.modules.validators.validate_link function uses the python-validators URL validation regex. This particular regular expression has an exponential complexity which allows an attacker to cause an application crash using a well-crafted argument..
Details
https://github.com/DedSecInside/TorBot/blob/d2b89192379ad033ffc7044efff26e16ccc02d5a/torbot/modules/validators.py#L13
An attacker can use a well-crafted URL argument to exploit the vulnerability in the regular expression and cause a Denial of Service on the system.
PoC
I have uploaded a secret gist containing a PoC (https://gist.github.com/ikkebr/6041055314f1cfb8e65b2a1acbaae12c). By adding one special character at the end of the user argument of the URL, the regular expression will take exponentially longer to compute.
For a string of size 10k, the regex will take 0.01s without the well-crafted URL and 1.3s with the well-crafted URL exploit. For a string of size 50k, the regex will take 0.03s without the well-crafted URL and 35s with the well-crafted URL exploit. For a string of size 100k, the regex will take 0.05s without the well-crafted URL and over 200s with the well-crafted URL exploit.
The regular expression used in the validators library versions [0.20, 0.11] is vulnerable to this attack. Version 0.21 appears to be unaffected, but it no longer contains a single regular expression.
Impact
An attacker could exploit this vulnerability to cause a denial of service or increased resource usage.
The vulnerability requires physical access to the device to be exploited. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the availability of the system.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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