CVE-2021-26690

HighPublished

mod_session NULL pointer dereference

Published: Jun 10, 2021
Updated: Aug 3, 2024
Assigning CNA: apache
Evidence observed: Aug 7, 2026

Primary CVSS

7.5/ 10High

nvd · CVSS 3.1

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS probability estimate

65.3%

High · next 30 days

Percentile: 99.3%
Model date: Oct 18, 2026

EPSS is a statistical estimate, not a certainty or a measure of impact. Combine it with CVSS, KEV status, exposure and your environment.

Summary

Apache HTTP Server versions 2.4.0 to 2.4.46 A specially crafted Cookie header handled by mod_session can cause a NULL pointer dereference and crash, leading to a possible Denial Of Service

Sources

CVE-2021-26690---Apache-mod_sessionExploit
CVE-2021-26690 patch diffing - Apache HTTP mod_session NULL pointer dereference
CVE-2021-26690PoC
Proof-of-concept exploit for CVE-2021-26690, demonstrating a specific web application vulnerability with exploitation code.

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