CVE Feed

    Dashboard / CVE / CVE-2021-26691

    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

    Published:Jun 4, 2021
    Last Modified:Nov 21, 2024
    EPS:Jun 10, 2021
    EPSS Score:0.49123
    CVSS Score:9.8

    Affected Products

    Vendor
    Apache
    Product
    Http Server
    Vendor
    Debian
    Product
    Debian Linux
    Vendor
    Fedoraproject
    Product
    Fedora
    Vendor
    Netapp
    Product
    Cloud Backup
    Vendor
    Oracle
    Product
    Enterprise Manager Ops Center
    Vendor
    Oracle
    Product
    Instantis Enterprisetrack
    Vendor
    Oracle
    Product
    Secure Backup
    Vendor
    Oracle
    Product
    Zfs Storage Appliance Kit
    Vendor
    Redhat
    Product
    Enterprise Linux
    Vendor
    Redhat
    Product
    Jboss Core Services

    Exploits

    https://github.com/dja2TaqkGEEfA45/CVE-2021-26691

    Related CVEs

    CVE-2026-48913 (CVSS 7.3) — Use After Free vulnerability in Apache HTTP Server module mod_http2 when file handles are already exhausted. …
    CVE-2026-42536 (CVSS 7.5) — Heap-based Buffer Overflow vulnerability in Apache HTTP Server with mod_xml2enc, xml2StartParse, and untrusted…
    CVE-2026-44185 (CVSS 7.3) — Buffer Over-read vulnerability in Apache HTTP Server via outbound OCSP requests to an attacker controlled OCSP…
    CVE-2026-34355 (CVSS 7.5) — A buffer overflow in mod_proxy_html in Apache HTTP Server 2.4.67 and earlier allows an attack by an untrusted …
    CVE-2026-44631 (CVSS 9.8) — Buffer Underwrite vulnerability in Apache HTTP Server on crafted regular expressions in the configuration. Th…
    CVE-2026-44119 (CVSS 5.5) — Improper Privilege Management vulnerability in Apache HTTP Server 2.4.67 and earlier allows local .htaccess au…
    CVE-2026-43951 (CVSS 6.5) — Out-of-bounds Read vulnerability in Apache HTTP Server with mod_headers and mod_mime and multiple response lan…
    CVE-2026-42535 (CVSS 9.1) — A path handling issue in mod_dav_fs in Apache 2.4.67 and earlier allows a WebDAV content author to directly ma…
    CVE-2026-34356 (CVSS 7.5) — Heap-based Buffer Overflow vulnerability in Apache HTTP Server with malicious backend servers and ProxyPassRev…
    CVE-2026-44186 (CVSS 7.3) — Loop with Unreachable Exit Condition ('Infinite Loop') vulnerability in the mod_proxy_ftp module in Apache HTT…

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

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High