5 Apache Vulnerabilities: Risks, Examples & Fixes Explained

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Key Takeaways

Apache vulnerabilities pose significant risks, including data breaches, denial-of-service attacks, and unauthorized server access.
Timely patching is critical, but official security support ends when a Linux distribution reaches the end of life.
TuxCare’s Endless Lifecycle Support delivers ongoing security updates, helping organizations keep Apache and other critical packages secure on EOL Linux systems.

Apache is commonly referred to the Apache HTTP server, a free and open-source cross-platform web server developed by the Apache Software Foundation. In 2025, several medium-severity vulnerabilities have been publicly disclosed in Apache HTTP Server 2.4.x versions. Because Apache is, and has been for quite some time, the de facto web server for the (majority of the) Internet, even low impact vulnerabilities affecting it can have far-reaching effects.

In this article, you will learn about Apache vulnerabilities, why they are dangerous, and how you can secure your Linux servers from the potential risks.

What Are Apache Vulnerabilities?

Apache vulnerabilities are security flaws or weaknesses found in the Apache HTTP server through which bad actors can gain unauthorized access, disrupt services, and perform other malicious activities. Since Apache, as a web server, hosts 25.5% of all the websites as of 2025, these flaws present a huge security problem to all sectors.

As of now in 2025, nine vulnerabilities have already been discovered in Apache HTTP Server 2.4.x versions, compared to 14 vulnerabilities reported in 2.4.x versions in 2024.

Common Types of Apache Vulnerabilities

Apache HTTP Server vulnerabilities typically fall into a few recurring categories. Understanding these helps organizations know what to watch for and why timely patching matters.

Remote Code Execution (RCE)

One of the most dangerous vulnerabilities, RCE allows attackers to run arbitrary commands on the server. With Apache, this often stems from input validation flaws or unsafe handling of user requests. An exploited RCE can lead to complete server takeover by a remote attacker — including data theft, malware installation, or using the compromised system to launch further attacks.

Path Traversal

Path traversal flaws occur when Apache improperly restricts access to directories and files. By manipulating URL paths (e.g., using ../), attackers are able to reach sensitive system files outside of the web root such as password hashes or configurations. These exposures often serve as stepping stones for deeper compromises. Notably, Apache HTTP Server vulnerabilities CVE-2021-41773 and CVE-2021-42013 both involved a path traversal that was then escalated to a remote code execution.

Denial of Service (DoS)

DoS vulnerabilities in Apache typically involve overwhelming the server with malformed requests or causing inefficient resource handling. A successful attack can lead to crashing the service, disrupting its operations, or degrading its performance. Even if there is no data stolen, downtime translates directly into financial loss and reputational harm. Reports show that for 25% of organizations, each hour of server downtime can cost between $300,000 and $400,000, making denial-of-service attacks a very costly risk.

Privilege Escalation

With some vulnerabilities, attackers who have limited access to the system may obtain a higher privilege. For example, CVE-2019-0211 enabled unprivileged Apache processes to execute commands as the root user. This kind of escalation increases the damage potential by allowing the attacker to bypass normal restrictions put in place by an enterprise security team and compromise the entire host environment.

Must Know: Misconfigurations can be sometimes more dangerous than vulnerabilities themselves. Weak permissions, default settings, or unused modules left enabled are common attack vectors that open doors for threat actors.

Recent Examples of Apache Vulnerabilities

In the following list of vulnerabilities, the affected versions of Apache start at version 2.4.0 up to and including version 2.4.63. Patches are already available for affected Linux distributions protected with Endless Lifecycle Support. You can view detailed information like CVEs, affected versions, and patch availability using the TuxCare’s CVE tracker.

Let’s take a closer look at the known vulnerabilities.

CVE-2024-47252

The first issue, CVE-2024-47252, affects Apache HTTP Server 2.4.63 and earlier. The problem lies in mod_ssl, where insufficient escaping of user-supplied input allows an attacker to insert escape characters into log files. The flaw is triggered in logging configurations that use directives like %{varname}x or %{varname}c with variables such as SSL_TLS_SNI. Because neither mod_ssl nor mod_log_config performed escaping, malicious data supplied by a client could end up unsanitized in logs. While this doesn’t directly compromise the server, it does allow attackers to manipulate or poison log records, which could hide traces of their activity from a security team or interfere with incident response efforts.

CVE-2025-23048

CVE-2025-23048 highlights a more concerning access control bypass in certain mod_ssl configurations. It affects Apache HTTP Server versions 2.4.35 through 2.4.63 when TLS 1.3 session resumption is enabled. In cases where multiple virtual hosts are each restricted to different client certificates, a flaw allows a client trusted on one host to gain access to another — but only if SSLStrictSNIVHostCheck isn’t enabled. Essentially, the separation between virtual hosts breaks down. This vulnerability undercuts the security guarantees expected when using client-side certificates for access control and has serious implications in multi-tenant environments.

CVE-2025-49630

This one, CVE-2025-49630, shows how configuration choices can expose Apache to denial-of-service risks. The vulnerability appears when Apache is set up as a reverse proxy for an HTTP/2 backend with ProxyPreserveHost turned on. Under those conditions, untrusted client input could trigger an assertion failure in the mod_proxy_http2 module, causing Apache to crash. While the flaw doesn’t grant attackers access to data or code execution, it does provide a reliable way to knock servers offline — a tactic often used in disruptive campaigns or as part of a larger attack chain.

CVE-2025-49812

CVE-2025-49812 is tied to mod_ssl configurations that use “SSLEngine optional” to allow TLS upgrades. In this setup, an attacker positioned in the middle of a connection could launch an HTTP desynchronization attack, executing session hijacking of active sessions during the TLS upgrade process. The end result is potential session takeover, with attackers impersonating legitimate users. Apache has addressed this by removing support for TLS upgrade in version 2.4.64, effectively eliminating the attack surface.

CVE-2024-40725

Finally, CVE-2024-40725 is a reminder that even fixes can introduce new problems. This one appeared in versions 2.4.60 and 2.4.61 as a partial fix for CVE-2024-39884. The flaw centers on the legacy use of directives like AddType for content-type based handler configuration. Under certain conditions, indirect file requests could expose the source code of local scripts, such as PHP, rather than executing them. The unintended disclosure of source code not only leaks sensitive logic but also provides attackers with valuable insights into how applications are built. Apache corrected the issue fully in version 2.4.62.

Note: Many Apache flaws don’t allow full server compromise on their own. Instead, they often act as a critical first step in a broader attack chain. Therefore, even low to medium-rated CVEs should be treated as urgent to prevent threat actors from escalating a minor flaw into a major breach.

Why Apache Vulnerabilities Are So Dangerous

Apache is one of the most widely used web servers in the world and this popularity also makes it a high-value target for attackers. A single unpatched Apache vulnerability can compromise not only a system but potentially thousands of websites and services simultaneously.

The other reason that Apache vulnerabilities are dangerous is because many are easy to exploit. Once a proof-of-concept (PoC) exploit is released in the public domain, attackers can automate scanning and exploitation on a massive scale. Tools like Metasploit make it trivial for even low-skilled attackers to launch attacks against unpatched servers.

The consequences of compromise can be severe:

Data breaches: In the event of a security breach, personal, financial, or business data are exposed.
Supply chain attacks: If your Apache server hosts applications or APIs consumed by partners, attackers can move downstream.
Brand damage: Security incidents related to high-profile Apache CVEs often make headlines, damaging brand reputation and customer trust.

Case study: In 2021, the Apache HTTP Server path traversal flaws (CVE-2021-41773 / CVE-2021-42013) were disclosed, and within hours to days, researchers observed widespread scanning of internet-facing servers. Many exploitation attempts have been reported soon after disclosure. The exploitation complexity was very low, making it easier for attackers to probe servers with crafted URLs. The attacks tried to access files containing information about the system, such as /etc/passwd, /etc/hosts, or even win.ini on Windows systems, which, ultimately, in some instances, may have disclosed credentials or configuration data, allowing for full system compromise.

How to Patch and Secure Apache HTTP Server

Securing your Apache HTTP Server is a continuous effort. Here are the most common approaches to patching and securing Apache.

Vendor Patches

The easiest way is to use official security updates provided by your Linux distribution. As long as your operating system is supported, security patches for the Apache HTTP Server and other packages are available through package managers apt (for Ubuntu/Debian) or yum/dnf (for RHEL/CentOS).

Manual Updates and Compilation

Another option is to download the latest Apache source code directly from Apache.org and compile it manually. While it ensures access to the latest version, this approach is recommended only for skilled users who can compile the package. Another disadvantage to using this method is that every new CVE needs manual intervention, so this requires ongoing attention and introduces the risk of consistent patching.

TuxCare’s Endless Lifecycle Support for Linux

What if your mission-critical server is running on a Linux distribution that has reached its end of life? With no official vendor patches made available, the system becomes vulnerable to new Apache vulnerabilities, including ones that can lead to a buffer overflow attack. This is the common and critical scenario for many organizations.

This is where extended support services like TuxCare’s Endless Lifecycle Support (ELS) are essential. ELS delivers ongoing security updates for your Apache HTTP Server and other various packages, even long after the official support ended. This approach provides vendor-grade protection while also giving your security team the time needed to plan a smooth migration without the pressure of rushing.

You can also learn more about managing Apache CXF EOL in our in-depth guide if your stack relies on open-source web services frameworks, or explore our guide on Apache Hive EOL if you utilize open-source data warehousing tools.

Protect Your Apache Servers with TuxCare’s ELS

Many organizations still rely on end-of-life Linux distributions and other open-source tools when security updates are no longer provided. While upgrading to a supported version is the long term solution to continue receiving security fixes, it is often challenging due to compatibility issues and downtime risks — not to mention the significant costs and time required to plan a smooth migration.

However, there is an alternative, cost-effective approach: TuxCare’s Endless Lifecycle Support (ELS). TuxCare supports a wide range of end-of-life Linux distributions, including: CentOS 6, CentOS 7, CentOS 8, CentOS Stream, Oracle Linux 6, Oracle Linux 7, Ubuntu 16.04, Ubuntu 18.04, Ubuntu 20.04, and RHEL 7.

ELS covers over 140 packages, including the Linux kernel updates and other critical packages like Apache, PHP, Python, MySQL, glibc, OpenSSL, OpenJDK, and more.

If you are already an Endless Lifecycle Support customer, the patches for above Apache vulnerabilities are ready and available for the affected systems. If not, now is the right time to explore how TuxCare’s ELS can keep your Apache servers — and your entire Linux stack — secure beyond end of life.

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