Security Experts:

High-Risk Flaw Haunts Apache Server

The Apache Software Foundation has released a new version of its flagship web server to patch a pair of security defects, one serious enough to lead to remote code execution attacks.

The Apache HTTP Server 2.4.52 is listed as urgent and the U.S. government’s security response agency CISA is calling on users of the open-source cross-platform web server software to “update as soon as possible.”

The patch provides cover for two documented security vulnerabilities  -- CVE-2021-44790 and CVE-2021-44224 -- one of which may allow a remote attacker to take control of an affected system.

From the Apache Software Foundation advisory:

HIGH: Possible buffer overflow when parsing multipart content in mod_lua of Apache HTTP Server 2.4.51 and earlier (CVE-2021-44790)

A carefully crafted request body can cause a buffer overflow in the mod_lua multipart parser (r:parsebody() called from Lua scripts).

The Apache httpd team is not aware of an exploit for the vulnerability though it might be possible to craft one.

The open-source group also documented CVE-2021-44224, a “moderate-risk” NULL dereference or SSRF in forward proxy configurations in Apache HTTP Server 2.4.51 and earlier.

“A crafted URI sent to httpd configured as a forward proxy (ProxyRequests on) can cause a crash (NULL pointer dereference) or, for configurations mixing forward and reverse proxy declarations, can allow for requests to be directed to a declared Unix Domain Socket endpoint (Server Side Request Forgery),” the Foundation said.

Security flaws in the Apache HTTP Server have been identified in the “known exploited vulnerabilities catalog” maintained by CISA.  The agency recently called attention to CVE-2021-40438, a Server-Side Request Forgery (SSRF) bug that’s already being exploited in the wild.

According to the latest market share data from Netcraft, the Apache HTTP Server continues to be dominant on the internet.

Related: Exploits Swirling for Major Security Defect in Apache Log4j

Related: CISA Adds Apache Server Flaw to 'Must-Patch' List

Related: Microsoft Spots Multiple Nation-State APTs Exploiting Log4j Flaw

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Ryan Naraine is Editor-at-Large at SecurityWeek and host of the popular Security Conversations podcast series. Ryan is a veteran cybersecurity strategist who has built security engagement programs at major global brands, including Intel Corp., Bishop Fox and Kaspersky GReAT. He is a co-founder of Threatpost and the global SAS conference series. Ryan's past career as a security journalist included bylines at major technology publications including Ziff Davis eWEEK, CBS Interactive's ZDNet, PCMag and PC World. Ryan is a director of the Security Tinkerers non-profit, an advisor to early-stage entrepreneurs, and a regular speaker at security conferences around the world. Follow Ryan on Twitter @ryanaraine.