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
Does this matter?
EPSS puts the probability of exploitation in the next 30 days at 68.3%, higher than 99% of all known CVEs. Patch or mitigate before the next change window.
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
- CVSS 3.1
- 9.8 CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- EPSS
- 68.29% probability · 99th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-122, CWE-787
- Affected
- apache/http server · debian/debian linux · fedoraproject/fedora · oracle/enterprise manager ops center · oracle/instantis enterprisetrack · oracle/secure backup · oracle/zfs storage appliance kit · netapp/cloud backup
- Source
- security@apache.org
EPSS 68.3% since 3 November 2026; no change recorded yet. The dashed line is the ten per cent mark our analysts treat as “patch before the next change window”. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
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/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%3EMailing List, Release Notes, Vendor Advisory
- https://lists.debian.org/debian-lts-announce/2021/07/msg00006.htmlMailing List, Third Party Advisory
- 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/202107-38Third 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/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%3EMailing List, Release Notes, Vendor Advisory
- https://lists.debian.org/debian-lts-announce/2021/07/msg00006.htmlMailing List, Third Party Advisory
- 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/202107-38Third 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
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.