CVE-2021-40438 vulnerability in Canonical and Other Products
Published on September 16, 2021
mod_proxy SSRF
Known Exploited Vulnerability
This Apache HTTP Server-Side Request Forgery (SSRF) vulnerability is part of CISA's list of Known Exploited Vulnerabilities. A crafted request uri-path can cause mod_proxy to forward the request to an origin server choosen by the remote user. This issue affects Apache HTTP Server 2.4.48 and earlier.
The following remediation steps are recommended / required by December 15, 2021: Apply updates per vendor instructions.
Vulnerability Analysis
CVE-2021-40438 is exploitable with network access, and does not require authorization privileges or user interaction. This vulnerability is consided to have a high level of attack complexity. This vulnerability is known to be actively exploited by threat actors. The potential impact of an exploit of this vulnerability is considered to be critical as this vulnerability has a high impact to the confidentiality, integrity and availability of this component.
Timeline
2.4.49 released
Weakness Type
What is a SSRF Vulnerability?
The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination. By providing URLs to unexpected hosts or ports, attackers can make it appear that the server is sending the request, possibly bypassing access controls such as firewalls that prevent the attackers from accessing the URLs directly. The server can be used as a proxy to conduct port scanning of hosts in internal networks, use other URLs such as that can access documents on the system (using file://), or use other protocols such as gopher:// or tftp://, which may provide greater control over the contents of requests.
CVE-2021-40438 has been classified to as a SSRF vulnerability or weakness.
Products Associated with CVE-2021-40438
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Affected Versions
Apache Software Foundation Apache HTTP Server:- Version Apache HTTP Server 2.4, <= 2.4.48 is affected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.