GET /icons/.%2e/ HTTP/1.1 Host: vulnerable-server.com
Beyond updating to a patched version, server administrators can take several steps to mitigate these vulnerabilities:
: When configured on a URL not upgraded by the origin server, it would tunnel the entire connection regardless, allowing subsequent requests to bypass HTTP validation, authentication, or authorization.
: A heap-based buffer overflow can be triggered by a specially crafted SessionHeader sent from an origin server. apache httpd 2.4.46 exploit
To protect against these vulnerabilities, the Apache Software Foundation has released updates to Apache httpd. Users of Apache httpd 2.4.46 and earlier should update to a version that includes the fixes for these vulnerabilities:
POST /cgi-bin/.%2e/bin/bash HTTP/1.1 Host: vulnerable-server.com Content-Type: application/x-www-form-urlencoded
If the server is vulnerable and the request is properly crafted, this could lead to remote code execution. GET /icons/
Apache mod_proxy Server-Side Request Forgery (SSRF) Vulnerability (CVE-2021-40438) * What is SSRF? Server-side request forgery is ... Qualys ThreatPROTECT Apache HTTP Server mod_proxy SSRF (CVE-2021-40438) Description. A Server-Side Request Forgery (SSRF) vulnerability exists in Apache HTTP Server versions 2.4. 48 and earlier when usi... Acunetix CVE-2021-40438: Apache HTTP Server SSRF CVE-2021-40438 is a Server-Side Request Forgery (SSRF) vulnerability found in Apache HTTP Server versions 2.4. 48 and earlier. The... UK Government Security CVE-2021-40438: Resf Rocky Linux SSRF Vulnerability - SentinelOne Mar 4, 2026 —
The primary security risks associated with Apache 2.4.46 revolve around memory corruption and improper handling of session headers. cve-2021-26691 - NVD
: This can lead to remote code execution (RCE) or a denial of service (DoS) by corrupting heap memory. mod_proxy_wstunnel (Tunneling Misconfiguration) : Vulnerability : CVE-2019-17567 . Users of Apache httpd 2
CVSS 4.0 Severity and Vector Strings: NIST: NVD. N/A. NVD assessment not yet provided. CVSS 3.x Severity and Vector Strings: NIST: National Institute of Standards and Technology (.gov) CVE-2021-26691: Apache HTTP Server Buffer Overflow Flaw
: Unexpected URL matching behavior occurs when MergeSlashes is set to OFF , potentially leading to security bypasses in access control. Remediation
