New Apache Web Server Bug Threatens Security of Shared Web Hosts

Apr 2, 2019

Mark J Cox, one of the founding members of the Apache Software
Foundation and the OpenSSL project, today posted a tweet warning users
about a recently discovered important flaw in Apache HTTP Server
software.

The Apache web server is one of the most popular, widely used
open-source web servers in the world that powers almost 40 percent
of the whole Internet.

The vulnerability, identified as CVE-2019-0211, was discovered
by Charles Fol, a security engineer at Ambionics Security
firm, and patched by the Apache developers in the latest version
2.4.39 of its software released today.

The flaw affects Apache HTTP Server versions 2.4.17 through 2.4.38
and could allow any less-privileged user to execute arbitrary code
with root privileges on the targeted server.

“In Apache HTTP Server 2.4 releases 2.4.17 to 2.4.38, with MPM
event, worker or prefork, code executing in less-privileged child
processes or threads (including scripts executed by an in-process
scripting interpreter) could execute arbitrary code with the
privileges of the parent process (usually root) by manipulating the
scoreboard. Non-Unix systems are not affected,” the advisory ^[2] says.

According to Cox, the vulnerability is more concerning for shared
web hosting services, where malicious customers or a hacker with
ability to execute PHP or CGI scripts on a website can make use of
the flaw to gain root access on the server, eventually compromising
all other websites hosted on the same server.

Besides this, the latest Apache httpd 2.4.39 version also
patches three low and two other important severity issues.

The second important flaw (CVE-2019-0217) could allow “a user
with valid credentials to authenticate using another username,
bypassing configured access control restrictions.”

The third vulnerability is a mod_ssl access control bypass
(CVE-2019-0215), “a bug in mod_ssl when using per-location client
certificate verification with TLSv1.3 allowed a client supporting
Post-Handshake Authentication to bypass configured access control
restrictions.”

We have seen how previous disclosures of severe flaws in web
application frameworks ^[3]
have resulted in PoC exploits being published within a day and
exploitation in the
wild ^[4], putting critical
infrastructure as well as customers’ data at risk.

Therefore, web hosting services, organizations managing their
own servers and website administrators are strongly advised to
upgrade their Apache HTTP instances to the latest versions as soon
as possible.

^[1]

References

^{^}
tweet
(twitter.com)
^{^}
advisory
(httpd.apache.org)
^{^}
flaws in web application frameworks
(thehackernews.com)
^{^}
exploitation in the wild
(thehackernews.com)

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OWASP TOP !0

Injection. Injection flaws, such as SQL, NoSQL, OS, and LDAP injection, occur when untrusted data is sent to an interpreter as part of a command or query. The attacker’s hostile data can trick the interpreter into executing unintended commands or accessing data without proper authorization. Broken Authentication. Application functions related to authentication and session management are often implemented incorrectly, allowing attackers to compromise passwords, keys, or session tokens, or to exploit other implementation flaws to assume other users’ identities temporarily or permanently. Sensitive Data Exposure. Many web applications and APIs do not properly protect sensitive data, such as financial, healthcare, and PII. Attackers may steal or modify such weakly protected data to conduct credit card fraud, identity theft, or other crimes. Sensitive data may be compromised without extra protection, such as encryption at rest or in transit, and requires special precautions when exchanged with the browser. XML External Entities (XXE). Many older or poorly configured XML processors evaluate external entity references within XML documents. External entities can be used to disclose internal files using the file URI handler, internal file shares, internal port scanning, remote code execution, and denial of service attacks. Broken Access Control. Restrictions on what authenticated users are allowed to do are often not properly enforced. Attackers can exploit these flaws to access unauthorized functionality and/or data, such as access other users’ accounts, view sensitive files, modify other users’ data, change access rights, etc. Security Misconfiguration. Security misconfiguration is the most commonly seen issue. This is commonly a result of insecure default configurations, incomplete or ad hoc configurations, open cloud storage, misconfigured HTTP headers, and verbose error messages containing sensitive information. Not only must all operating systems, frameworks, libraries, and applications be securely configured, but they must be patched/upgraded in a timely fashion. Cross-Site Scripting XSS. XSS flaws occur whenever an application includes untrusted data in a new web page without proper validation or escaping, or updates an existing web page with user-supplied data using a browser API that can create HTML or JavaScript. XSS allows attackers to execute scripts in the victim’s browser which can hijack user sessions, deface web sites, or redirect the user to malicious sites. Insecure Deserialization. Insecure deserialization often leads to remote code execution. Even if deserialization flaws do not result in remote code execution, they can be used to perform attacks, including replay attacks, injection attacks, and privilege escalation attacks. Using Components with Known Vulnerabilities. Components, such as libraries, frameworks, and other software modules, run with the same privileges as the application. If a vulnerable component is exploited, such an attack can facilitate serious data loss or server takeover. Applications and APIs using components with known vulnerabilities may undermine application defenses and enable various attacks and impacts. Insufficient Logging & Monitoring. Insufficient logging and monitoring, coupled with missing or ineffective integration with incident response, allows attackers to further attack systems, maintain persistence, pivot to more systems, and tamper, extract, or destroy data. Most breach studies show time to detect a breach is over 200 days, typically detected by external parties rather than internal processes or monitoring.

New Apache Web Server Bug Threatens Security of Shared Web Hosts

References

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