CVE-2021-26691
CRITICALCVSS 9.8/10EPSS 68.07%
Last modified
CVE-2021-26691 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. 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. EPSS estimates a 68.07% chance of exploitation in the next 30 days.
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
Metrics
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness Enumeration
Affected Software
| Vendor | Product | Versions |
|---|---|---|
| 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 | Secure Backup | < 18.1.0.1.0 |
| Oracle | Zfs Storage Appliance Kit | 8.8 |
| Netapp | Cloud Backup | All versions |
References
- http://httpd.apache.org/security/vulnerabilities_24.htmlVendor Advisory
- http://www.openwall.com/lists/oss-security/2021/06/10/7Mailing List, Third Party Advisory
- https://lists.apache.org/thread.html/re026d3da9d7824bd93b9f871c0fdda978d960c7e62d8c43cba8d0bf3%40%3Ccvs.httpd.apache.org%3EMailing List, Release Notes, Vendor Advisory
- https://lists.debian.org/debian-lts-announce/2021/07/msg00006.htmlMailing List, Third Party Advisory
- https://security.gentoo.org/glsa/202107-38Third Party Advisory
- https://security.netapp.com/advisory/ntap-20210702-0001/Third Party Advisory
- https://www.debian.org/security/2021/dsa-4937Mailing List, Third Party Advisory
- https://www.oracle.com/security-alerts/cpujan2022.htmlPatch, Third Party Advisory
- https://www.oracle.com/security-alerts/cpuoct2021.htmlPatch, Third Party Advisory
- http://httpd.apache.org/security/vulnerabilities_24.htmlVendor Advisory
- http://www.openwall.com/lists/oss-security/2021/06/10/7Mailing List, Third Party Advisory
- https://lists.apache.org/thread.html/re026d3da9d7824bd93b9f871c0fdda978d960c7e62d8c43cba8d0bf3%40%3Ccvs.httpd.apache.org%3EMailing List, Release Notes, Vendor Advisory
- https://lists.debian.org/debian-lts-announce/2021/07/msg00006.htmlMailing List, Third Party Advisory
- https://security.gentoo.org/glsa/202107-38Third Party Advisory
- https://security.netapp.com/advisory/ntap-20210702-0001/Third Party Advisory
- https://www.debian.org/security/2021/dsa-4937Mailing List, Third Party Advisory
- https://www.oracle.com/security-alerts/cpujan2022.htmlPatch, Third Party Advisory
- https://www.oracle.com/security-alerts/cpuoct2021.htmlPatch, Third Party Advisory
Timeline
- Published
- Last Modified
- Status
- Modified
Frequently Asked Questions
What is CVE-2021-26691?
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
How severe is CVE-2021-26691?
CVE-2021-26691 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 68.07% probability of exploitation in the next 30 days.
How do I fix CVE-2021-26691?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.
How Strix Helps
- How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
- Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
- PR ReviewsPentest every pull request so vulnerable code is caught before it ships to production.
- AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.
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