CVE-2021-26690

mediumpriority · attend · 63EPSS 0.653 · 99 %ileexploit · PoCDEEURUUS

grimoire priorityP1 · Urgent

Exploitable?

Public exploit

2 exploits · PoC

Likely / severe?

65.3% (99th) EPSS

CVSS 5 · medium

Is it mine?

67 products

Check your exposure

Who says so?

5 sources

cnnvd · enisa_euvd · fstec_bdu · cert_bund

EPSS · scored 2026-10-25

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

cvss

Technical severity, 0–10. One row per scoring source.

7.5

010

base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · medium–high · 5–7.5

v2.05mediumAV:N/AC:L/Au:N/C:N/I:N/A:Pprimary · NVD / NIST USexploitability 10 · impact 2.9

v3.17.5highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Hprimary · NVD / NIST USexploitability 3.9 · impact 3.6

v3.17.5highAV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Hsecondary · FSTEC (BDU) RU

v3.17.5highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:Hsecondary · CVSS-BT (t0sche)

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-476USprimaryCWE-476US

exploits (2)

Public proof-of-concept and weaponised exploit code.

7own/CVE-2021-26690---Apache-mod_sessionCVE-2021-26690 patch diffing - Apache HTTP mod_session NULL pointer dereferencePoC · poc_in_github
danielduan2002/CVE-2021-26690danielduan2002/CVE-2021-26690PoC · poc_in_github

affected products (67)

Products and version ranges known to be affected.

Juniper JUNOSall versionscert_bundDEcpe:/o:juniper:junos:-
Apache Software Foundation Apache HTTP Server≤ 2.4.12enisa_euvdEU
Apache Software Foundation Apache HTTP Server≤ 2.4.35enisa_euvdEU
Apache Software Foundation Apache HTTP Server≤ 2.4.7enisa_euvdEU
Apache Software Foundation Apache HTTP Server≤ 2.4.17enisa_euvdEU
Apache Software Foundation Apache HTTP Server≤ 2.4.16enisa_euvdEU
Apache Software Foundation Apache HTTP Server≤ 2.4.23enisa_euvdEU
Apache Software Foundation Apache HTTP Server≤ 2.4.29enisa_euvdEU
Apache Software Foundation Apache HTTP Server≤ 2.4.0enisa_euvdEU
Apache Software Foundation Apache HTTP Server≤ 2.4.6enisa_euvdEU
Apache Software Foundation Apache HTTP Server≤ 2.4.43enisa_euvdEU
Apache Software Foundation Apache HTTP Server≤ 2.4.37enisa_euvdEU
Apache Software Foundation Apache HTTP Server≤ 2.4.3enisa_euvdEU
Apache Software Foundation Apache HTTP Server≤ 2.4.25enisa_euvdEU
Apache Software Foundation Apache HTTP Server≤ 2.4.20enisa_euvdEU
Apache Software Foundation Apache HTTP Server≤ 2.4.33enisa_euvdEU
Apache Software Foundation Apache HTTP Server≤ 2.4.26enisa_euvdEU
Apache Software Foundation Apache HTTP Server≤ 2.4.39enisa_euvdEU
Apache Software Foundation Apache HTTP Server≤ 2.4.41enisa_euvdEU
Apache Software Foundation Apache HTTP Server≤ 2.4.34enisa_euvdEU

showing 20 of 67

advisories (3)

Vendor and ecosystem advisories describing this.

WID-SEC-W-2022-0438Apache HTTP Server: Mehrere SchwachstellenDeutsch2021-06-09csaf · cert_bundDE
Ein entfernter, anonymer Angreifer kann mehrere Schwachstellen in Apache HTTP Server ausnutzen, um einen Denial of Service Angriff durchzuführen, Sicherheitsvorkehrungen zu umgehen oder sonstige Auswirkungen zu verursachen.
WID-SEC-W-2024-1591Juniper JUNOS: Mehrere SchwachstellenDeutsch2024-07-10csaf · cert_bundDE
Ein Angreifer kann mehrere Schwachstellen in Juniper JUNOS ausnutzen, um einen Denial of Service zu verursachen, Informationen offenzulegen, Privilegien zu erweitern und Sicherheitsmechanismen inklusive zu umgehen.
BIT-apache-2021-26690mod_session NULL pointer dereference2024-03-06vendor · osvUS
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

also known as (4)

Other names and identifiers for this entity.

sources

Which sources assert this record, and when.

cnnvd enisa_euvd fstec_bdu cert_bund osv NVD CVE.org MITRE

published 2021-06-10modified 2026-06-17

related (8,756)

Related entries.

ID	severity	EPSS	exploitable	published
CVE-2026-21525US	—OT critical	4.83% (92nd)	KEV	2026-02-10
Null pointer dereference in Windows Remote Access Connection Manager allows an unauthorized attacker to deny service locally.
CVE-2010-0425US	high10.0	94.2% (100th)	Exploit	2010-03-05
modules/arch/win32/mod_isapi.c in mod_isapi in the Apache HTTP Server 2.0.37 through 2.0.63, 2.2.0 through 2.2.14, and 2.3.x before 2.3.7, when running on Windows, does not ensure…
CVE-2012-0779US	high9.3	87.1% (100th)	Exploit	2012-05-04
Adobe Flash Player before 10.3.183.19 and 11.x before 11.2.202.235 on Windows, Mac OS X, and Linux; before 11.1.111.9 on Android 2.x and 3.x; and before 11.1.115.8 on Android 4.x a…
CVE-2012-5896US	high10.0	68.7% (99th)	Exploit	2012-11-17
The Annotation Objects Extension ActiveX control in AnnotateX.dll in Quest InTrust 10.4.0.853 and earlier does not properly implement the Add method, which allows remote attackers…
CVE-2003-0772US	high7.5	84.9% (100th)	Exploit	2003-09-22
Multiple buffer overflows in WS_FTP 3 and 4 allow remote authenticated users to cause a denial of service and possibly execute arbitrary code via long (1) APPE (append) or (2) STAT…

+8751 more

references (57)

External citations — patches, advisories, analysis.

scry

Attackers weaponise vulnerabilities like this against internet-exposed services. See what is exposed on your perimeter with a free passive scan.

Free scan