What’s Vulnerable › Vulnerabilities
CVE-2021-26691: Apache HTTP Server mod_session response handling heap overflow
- Severity: critical (CVSS 9.8 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 68.3% probability of exploitation in the next 30 days
- Public exploit or detection template: none known
- Published: 2021-06-10 · updated 2026-06-17
- Weakness: CWE-122
Description
In Apache HTTP Server versions 2.4.0 to 2.4.46 a specially crafted SessionHeader sent by an origin server could cause a heap overflow
Affected products
- Apache HTTP Server: from 2.4.0 through 2.4.46
- Debian Linux: 9.0, 10.0
- Fedoraproject Fedora: 34, 35
- NetApp Cloud Backup: all versions
- Oracle Corporation Enterprise Manager Ops Center: 12.4.0.0
- Oracle Instantis Enterprisetrack: 17.1, 17.2, 17.3
- Oracle Corporation Oracle Secure Backup: before 18.1.0.1.0 — fixed in 18.1.0.1.0
- Oracle Corporation Oracle ZFS Storage Appliance Kit: 8.8
How to fix
Upgrade to a fixed version: Oracle Corporation Oracle Secure Backup 18.1.0.1.0. Check the vendor advisory for mitigations.
References
- http://httpd.apache.org/security/vulnerabilities_24.html
- http://www.openwall.com/lists/oss-security/2021/06/10/7
- https://lists.apache.org/thread.html/r50cae1b71f1e7421069036b213c26da7d8f47dd59874e3bd956959fe%40%3Cannounce.httpd.apache.org%3E
- https://lists.apache.org/thread.html/r7f2b70b621651548f4b6f027552f1dd91705d7111bb5d15cda0a68dd%40%3Cdev.httpd.apache.org%3E
- https://lists.apache.org/thread.html/re026d3da9d7824bd93b9f871c0fdda978d960c7e62d8c43cba8d0bf3%40%3Ccvs.httpd.apache.org%3E
- https://lists.debian.org/debian-lts-announce/2021/07/msg00006.html
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/SPBR6WUYBJNACHKE65SPL7TJOHX7RHWD/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZNCYSR3BXT36FFF4XTCPL3HDQK4VP45R/
- https://security.gentoo.org/glsa/202107-38
- https://security.netapp.com/advisory/ntap-20210702-0001/
- https://www.debian.org/security/2021/dsa-4937
- https://www.oracle.com/security-alerts/cpujan2022.html
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