CVE-2021-26690

HIGH

Apache HTTP Server 2.4.0-2.4.46 - Denial of Service via Crafted Cookie Header in mod_session

Title source: llm

Exploitation Summary

EIP tracks 2 public exploits for CVE-2021-26690. PoCs published by 7own, danielduan2002.

AI-analyzed exploit summary This repository provides a technical analysis of CVE-2021-26690, a NULL pointer dereference in Apache's mod_session module leading to DoS. It includes a curl command to trigger the vulnerability and discusses limitations such as encryption via mod_session_crypto.

Description

Apache HTTP Server versions 2.4.0 to 2.4.46 A specially crafted Cookie header handled by mod_session can cause a NULL pointer dereference and crash, leading to a possible Denial Of Service

Exploits (2)

nomisec WRITEUP 1 stars

by 7own · poc

https://github.com/7own/CVE-2021-26690---Apache-mod_session

View Code ZIP pw:eip

This repository provides a technical analysis of CVE-2021-26690, a NULL pointer dereference in Apache's mod_session module leading to DoS. It includes a curl command to trigger the vulnerability and discusses limitations such as encryption via mod_session_crypto.

Classification

Writeup 90%

Attack Type

Dos

Complexity

Trivial

Reliability

Reliable

Target: Apache HTTP Server with mod_session

No auth needed

Prerequisites: Apache HTTP Server with mod_session enabled · No SessionCryptoPassphrase configured

MITRE ATT&CK

T1499 - Endpoint Denial of Service

devstral-2 · analyzed Feb 18, 2026 Full analysis →

nomisec NO CODE

by danielduan2002 · poc

https://github.com/danielduan2002/CVE-2021-26690

View Code ZIP pw:eip

References (12)

Core 12

Core References

Release Notes, Vendor Advisory x_refsource_misc

http://httpd.apache.org/security/vulnerabilities_24.html

Mailing List, Vendor Advisory x_refsource_misc

https://lists.apache.org/thread.html/re026d3da9d7824bd93b9f871c0fdda978d960c7e62d8c43cba8d0bf3%40%3Ccvs.httpd.apache.org%3E

Mailing List mailing-list x_refsource_mlist

https://lists.apache.org/thread.html/rae406c1d19c0dfd3103c96923dadac2af1cd0bad6905ab1ede153865%40%3Cannounce.httpd.apache.org%3E

Mailing List mailing-list x_refsource_mlist

https://lists.apache.org/thread.html/r7f2b70b621651548f4b6f027552f1dd91705d7111bb5d15cda0a68dd%40%3Cdev.httpd.apache.org%3E

Mailing List, Third Party Advisory mailing-list x_refsource_mlist

http://www.openwall.com/lists/oss-security/2021/06/10/6

Mailing List, Third Party Advisory mailing-list x_refsource_mlist

https://lists.debian.org/debian-lts-announce/2021/07/msg00006.html

Mailing List, Third Party Advisory vendor-advisory x_refsource_debian

https://www.debian.org/security/2021/dsa-4937

Third Party Advisory vendor-advisory x_refsource_gentoo

https://security.gentoo.org/glsa/202107-38

Mailing List, Third Party Advisory vendor-advisory x_refsource_fedora

https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/SPBR6WUYBJNACHKE65SPL7TJOHX7RHWD/

Mailing List, Third Party Advisory vendor-advisory x_refsource_fedora

https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZNCYSR3BXT36FFF4XTCPL3HDQK4VP45R/

Third Party Advisory x_refsource_misc

https://www.oracle.com/security-alerts/cpuoct2021.html

Third Party Advisory x_refsource_confirm

https://security.netapp.com/advisory/ntap-20210702-0001/

Scores

CVSS v3 7.5

EPSS 0.6507

EPSS Percentile 99.1%

Attack Vector NETWORK

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Details

CWE

CWE-476

Status published

Products (10)

apache/http_server 2.4.0 - 2.4.46

debian/debian_linux 9.0

debian/debian_linux 10.0

fedoraproject/fedora 34

fedoraproject/fedora 35

oracle/enterprise_manager_ops_center 12.4.0.0

oracle/instantis_enterprisetrack 17.1

oracle/instantis_enterprisetrack 17.2

oracle/instantis_enterprisetrack 17.3

oracle/zfs_storage_appliance_kit 8.8

Published Jun 10, 2021

Tracked Since Feb 18, 2026