Critical
Security advisory
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
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2021-26691
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 1 Nov 2026, 07:39 UTC · Revision 1
Source evidence
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
osv:CVE-2021-26691
Complete source record
{
"id": "c32eecdc7330f79e6d3e9294062f7e5af9e74925aafe2ac41f6e606245a4cd03",
"url": "https://osv.dev/vulnerability/CVE-2021-26691",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "CVE-2021-26691",
"summary": "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",
"evidence": "osv:CVE-2021-26691",
"products": [],
"severity": "critical",
"structured": {
"id": "CVE-2021-26691",
"aliases": [
"BIT-apache-2021-26691",
"CVE-2021-26691"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
}
],
"affected": [
{
"ranges": [
{
"repo": "https://github.com/apache/httpd",
"type": "GIT",
"events": [
{
"introduced": "da5873e80d6eee7a0838793bf68f1d0254745fbb"
},
{
"last_affected": "8064ccc50bffe86ad464246b9bfac7d78d7dbc1f"
}
],
"database_specific": {
"extracted_events": [
{
"cpe": "cpe:2.3:a:apache:http_server:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "2.4.0"
},
{
"last_affected": "2.4.46"
}
],
"source": "CPE_RANGE"
}
]
}
}
],
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2021-26691.json"
}
}
],
"modified": "2026-10-24T10:30:56.213003872Z",
"provider": "osv",
"references": [
"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.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://lists.apache.org/thread.html/re026d3da9d7824bd93b9f871c0fdda978d960c7e62d8c43cba8d0bf3%40%3Ccvs.httpd.apache.org%3E",
"https://lists.debian.org/debian-lts-announce/2021/07/msg00006.html",
"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"
],
"provider_metadata": {
"unresolved_ranges": [
{
"cpes": [
"cpe:2.3:a:oracle:secure_backup:*:*:*:*:*:*:*:*"
],
"vendor_product": "oracle:secure_backup",
"extracted_events": [
{
"range": [
{
"fixed": "18.1.0.1.0"
}
],
"source": "CPE_RANGE"
}
]
},
{
"cpes": [
"cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*",
"cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*"
],
"vendor_product": "debian:debian_linux",
"extracted_events": [
{
"range": [
{
"introduced": "9.0"
},
{
"last_affected": "9.0"
},
{
"introduced": "10.0"
},
{
"last_affected": "10.0"
}
],
"source": "CPE_STRING"
}
]
},
{
"cpes": [
"cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*",
"cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:*"
],
"vendor_product": "fedoraproject:fedora",
"extracted_events": [
{
"range": [
{
"introduced": "34"
},
{
"last_affected": "34"
},
{
"introduced": "35"
},
{
"last_affected": "35"
}
],
"source": "CPE_STRING"
}
]
},
{
"cpes": [
"cpe:2.3:a:oracle:enterprise_manager_ops_center:12.4.0.0:*:*:*:*:*:*:*"
],
"vendor_product": "oracle:enterprise_manager_ops_center",
"extracted_events": [
{
"range": [
{
"introduced": "12.4.0.0"
},
{
"last_affected": "12.4.0.0"
}
],
"source": "CPE_STRING"
}
]
},
{
"cpes": [
"cpe:2.3:a:oracle:instantis_enterprisetrack:17.1:*:*:*:*:*:*:*",
"cpe:2.3:a:oracle:instantis_enterprisetrack:17.2:*:*:*:*:*:*:*",
"cpe:2.3:a:oracle:instantis_enterprisetrack:17.3:*:*:*:*:*:*:*"
],
"vendor_product": "oracle:instantis_enterprisetrack",
"extracted_events": [
{
"range": [
{
"introduced": "17.1"
},
{
"last_affected": "17.1"
},
{
"introduced": "17.2"
},
{
"last_affected": "17.2"
},
{
"introduced": "17.3"
},
{
"last_affected": "17.3"
}
],
"source": "CPE_STRING"
}
]
},
{
"cpes": [
"cpe:2.3:a:oracle:zfs_storage_appliance_kit:8.8:*:*:*:*:*:*:*"
],
"vendor_product": "oracle:zfs_storage_appliance_kit",
"extracted_events": [
{
"range": [
{
"introduced": "8.8"
},
{
"last_affected": "8.8"
}
],
"source": "CPE_STRING"
}
]
}
]
}
},
"related_cves": [
{
"value": "CVE-2021-26691",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 438611,
"published_at": "2021-06-10T07:15:07.58+00:00"
}