Security readout for executives and security teams
CVE-2021-26691 is a heap overflow in Apache HTTP Server's mod_session handling. A crafted SessionHeader from an origin server could corrupt server memory. Exposure depends on running affected Apache 2.4.0 through 2.4.46 and using the relevant session functionality. Likely exposed assets are Apache HTTP Server 2.4.0-2.4.46 deployments where mod_session is enabled and processes SessionHeader values from origin responses. Standard package-managed Apache installations may be covered by Debian, Gentoo, Fedora, Oracle, or NetApp advisories if applicable. Treat this as a remediation tracking item for Apache fleets, especially systems using session modules or reverse-proxy patterns. It deserves timely patching, but the source bundle does not support emergency active-exploitation language. Mitigation focus: Identify Apache HTTP Server versions 2.4.0 through 2.4.46.; Check whether mod_session is enabled on exposed or proxying servers.; Apply Apache or operating-system vendor security updates..
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
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CWE-122: Exact CWE lookup
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Open ATT&CK lookupCVE-2021-26691 mapping review
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Open ATT&CK lookup- Severity
- Unknown
- CVSS
- Not scored
- Known Exploited
- No
- Published
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS and timeline data
No CVSS vectors or timeline events were available in the normalized CVE source material.
Source materials
- CVE List V5 sourceCVE List V5
- https://lists.apache.org/thread.html/re026d3da9d7824bd93b9f871c0fdda978d960c7e62d8c43cba8d0bf3%40%3Ccvs.httpd.apache.org%3ECVE reference · x_refsource_MISC
- [httpd-announce] 20210609 CVE-2021-26691: mod_session response handling heap overflowCVE reference · mailing-list, x_refsource_MLIST
- [httpd-dev] 20210610 Re: svn commit: r1890598 - in /httpd/site/trunk/content/security/json: CVE-2019-17567.json CVE-2020-13938.json CVE-2020-13950.json CVE-2020-35452.json CVE-2021-26690.json CVE-2021-26691.json CVE-2021-30641.json CVE-2021-31618.jsonCVE reference · mailing-list, x_refsource_MLIST
- [debian-lts-announce] 20210709 [SECURITY] [DLA 2706-1] apache2 security updateCVE reference · mailing-list, x_refsource_MLIST
- DSA-4937CVE reference · vendor-advisory, x_refsource_DEBIAN
- GLSA-202107-38CVE reference · vendor-advisory, x_refsource_GENTOO
- FEDORA-2021-dce7e7738eCVE reference · vendor-advisory, x_refsource_FEDORA
- FEDORA-2021-e3f6dd670dCVE reference · vendor-advisory, x_refsource_FEDORA
- https://www.oracle.com/security-alerts/cpuoct2021.htmlCVE reference · x_refsource_MISC
- https://security.netapp.com/advisory/ntap-20210702-0001/CVE reference · x_refsource_CONFIRM
- https://www.oracle.com/security-alerts/cpujan2022.htmlCVE reference · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Heap-based Buffer Overflow
Heap-based Buffer Overflow represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.