Search for vulnerabilities
Vulnerability details: VCID-3uab-583c-r3dp
Vulnerability ID VCID-3uab-583c-r3dp
Aliases CVE-2021-26691
Summary 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
Status Published
Exploitability 0.5
Weighted Severity 8.8
Risk 4.4
Affected and Fixed Packages Package Details
Weaknesses (2)
CWE-119 Improper Restriction of Operations within the Bounds of a Memory Buffer
CWE-787 Out-of-bounds Write
System Score Found at
cvssv3 8.1 https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2021-26691.json
epss 0.44379 https://api.first.org/data/v1/epss?cve=CVE-2021-26691
epss 0.47495 https://api.first.org/data/v1/epss?cve=CVE-2021-26691
epss 0.47495 https://api.first.org/data/v1/epss?cve=CVE-2021-26691
epss 0.47495 https://api.first.org/data/v1/epss?cve=CVE-2021-26691
epss 0.47495 https://api.first.org/data/v1/epss?cve=CVE-2021-26691
epss 0.47495 https://api.first.org/data/v1/epss?cve=CVE-2021-26691
epss 0.47495 https://api.first.org/data/v1/epss?cve=CVE-2021-26691
epss 0.47495 https://api.first.org/data/v1/epss?cve=CVE-2021-26691
epss 0.47495 https://api.first.org/data/v1/epss?cve=CVE-2021-26691
cvssv3.1 7.5 https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
apache_httpd low https://httpd.apache.org/security/json/CVE-2021-26691.json
cvssv2 7.5 https://nvd.nist.gov/vuln/detail/CVE-2021-26691
cvssv3.1 9.8 https://nvd.nist.gov/vuln/detail/CVE-2021-26691
archlinux Medium https://security.archlinux.org/AVG-2053
Reference id Reference type URL
https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2021-26691.json
https://api.first.org/data/v1/epss?cve=CVE-2021-26691
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-35452
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-26690
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-26691
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-30641
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-31618
https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
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://security.netapp.com/advisory/ntap-20210702-0001/
https://www.oracle.com/security-alerts/cpujan2022.html
https://www.oracle.com/security-alerts/cpuoct2021.html
http://www.openwall.com/lists/oss-security/2021/06/10/7
1966732 https://bugzilla.redhat.com/show_bug.cgi?id=1966732
AVG-2053 https://security.archlinux.org/AVG-2053
cpe:2.3:a:apache:http_server:*:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:apache:http_server:*:*:*:*:*:*:*:*
cpe:2.3:a:netapp:cloud_backup:-:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:netapp:cloud_backup:-:*:*:*:*:*:*:*
cpe:2.3:a:oracle:enterprise_manager_ops_center:12.4.0.0:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:oracle:enterprise_manager_ops_center:12.4.0.0:*:*:*:*:*:*:*
cpe:2.3:a:oracle:instantis_enterprisetrack:17.1:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:oracle:instantis_enterprisetrack:17.1:*:*:*:*:*:*:*
cpe:2.3:a:oracle:instantis_enterprisetrack:17.2:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:oracle:instantis_enterprisetrack:17.2:*:*:*:*:*:*:*
cpe:2.3:a:oracle:instantis_enterprisetrack:17.3:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:oracle:instantis_enterprisetrack:17.3:*:*:*:*:*:*:*
cpe:2.3:a:oracle:secure_backup:*:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:oracle:secure_backup:*:*:*:*:*:*:*:*
cpe:2.3:a:oracle:zfs_storage_appliance_kit:8.8:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:oracle:zfs_storage_appliance_kit:8.8:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:*
CVE-2021-26691 https://httpd.apache.org/security/json/CVE-2021-26691.json
CVE-2021-26691 https://nvd.nist.gov/vuln/detail/CVE-2021-26691
RHSA-2021:3816 https://access.redhat.com/errata/RHSA-2021:3816
RHSA-2021:4613 https://access.redhat.com/errata/RHSA-2021:4613
RHSA-2021:4614 https://access.redhat.com/errata/RHSA-2021:4614
RHSA-2022:0143 https://access.redhat.com/errata/RHSA-2022:0143
USN-4994-1 https://usn.ubuntu.com/4994-1/
USN-4994-2 https://usn.ubuntu.com/4994-2/
No exploits are available.
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H Found at https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2021-26691.json
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Found at https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: AV:N/AC:L/Au:N/C:P/I:P/A:P Found at https://nvd.nist.gov/vuln/detail/CVE-2021-26691
Exploitability (E) Access Vector (AV) Access Complexity (AC) Authentication (Au) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

high

functional

unproven

proof_of_concept

not_defined

local

adjacent_network

network

high

medium

low

multiple

single

none

none

partial

complete

none

partial

complete

none

partial

complete
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Found at https://nvd.nist.gov/vuln/detail/CVE-2021-26691
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Exploit Prediction Scoring System (EPSS)
Percentile 0.97447
EPSS Score 0.44379
Published At July 30, 2025, 12:55 p.m.
Date Actor Action Source VulnerableCode Version
2025-07-31T08:29:08.555393+00:00 Apache HTTPD Importer Import https://httpd.apache.org/security/json/CVE-2021-26691.json 37.0.0