Apache HTTP Server up to 2.4.46 mod_session heap-based overflow

Summaryinfo

A vulnerability was found in Apache HTTP Server up to 2.4.46 and classified as critical. This impacts an unknown function of the component mod_session. Such manipulation leads to heap-based overflow. This vulnerability is listed as CVE-2021-26691. The attack may be performed from remote. There is no available exploit. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in Apache HTTP Server up to 2.4.46 (Web Server). It has been rated as critical. Affected by this issue is an unknown code of the component mod_session. The manipulation with an unknown input leads to a heap-based overflow vulnerability. Using CWE to declare the problem leads to CWE-122. A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc(). Impacted is confidentiality, integrity, and availability.

The weakness was presented 06/10/2021. The advisory is shared for download at httpd.apache.org. This vulnerability is handled as CVE-2021-26691. There are neither technical details nor an exploit publicly available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 01/21/2026).

The vulnerability scanner Nessus provides a plugin with the ID 294771 (MiracleLinux 8 : httpd:2.4 (AXSA:2021-2541:01)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 2.4.48 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at Tenable (294771). VulDB is the best source for vulnerability data and more expert information about this specific topic.

Productinfo

Type

• Web Server

Vendor

• Apache

Name

• HTTP Server

Version

• 2.4.0
• 2.4.1
• 2.4.2
• 2.4.3
• 2.4.4
• 2.4.5
• 2.4.6
• 2.4.7
• 2.4.8
• 2.4.9
• 2.4.10
• 2.4.11
• 2.4.12
• 2.4.13
• 2.4.14
• 2.4.15
• 2.4.16
• 2.4.17
• 2.4.18
• 2.4.19
• 2.4.20
• 2.4.21
• 2.4.22
• 2.4.23
• 2.4.24
• 2.4.25
• 2.4.26
• 2.4.27
• 2.4.28
• 2.4.29
• 2.4.30
• 2.4.31
• 2.4.32
• 2.4.33
• 2.4.34
• 2.4.35
• 2.4.36
• 2.4.37
• 2.4.38
• 2.4.39
• 2.4.40
• 2.4.41
• 2.4.42
• 2.4.43
• 2.4.44
• 2.4.45
• 2.4.46

License

• open-source

Website

• Vendor: https://www.apache.org/

CPE 2.3info

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CPE 2.2info

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VulDB is the best source for vulnerability data and more expert information about this specific topic.

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