Summary
TorBot vulnerable to Inefficient Regular Expression Complexity in validate_link
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
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.
A regular expression with worst-case exponential or polynomial matching time is applied to untrusted input, causing excessive CPU use. Typical impact: denial of service when input is crafted to trigger backtracking.
CVE-2023-45813 has a CVSS score of 4.6 (Medium). The vector is requires physical access, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (4.0.0); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2023-45813? CVE-2023-45813 is a medium-severity inefficient regular expression (ReDoS) vulnerability in torbot (pip), affecting versions < 4.0.0. It is fixed in 4.0.0. A regular expression with worst-case exponential or polynomial matching time is applied to untrusted input, causing excessive CPU use.
- How severe is CVE-2023-45813? CVE-2023-45813 has a CVSS score of 4.6 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of torbot are affected by CVE-2023-45813? torbot (pip) versions < 4.0.0 is affected.
- Is there a fix for CVE-2023-45813? Yes. CVE-2023-45813 is fixed in 4.0.0. Upgrade to this version or later.
- Is CVE-2023-45813 exploitable, and should I be worried? Whether CVE-2023-45813 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2023-45813 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2023-45813? Upgrade
torbotto 4.0.0 or later.