Description
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
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Apache Software Foundation | Apache HTTP Server | 2.4.46, 2.4.43, 2.4.41, 2.4.39, 2.4.38, 2.4.37, 2.4.35, 2.4.34, 2.4.33, 2.4.29, 2.4.28, 2.4.27, 2.4.26, 2.4.25, 2.4.23, 2.4.20, 2.4.18, 2.4.17, 2.4.16, 2.4.12, 2.4.10, 2.4.9, 2.4.7, 2.4.6, 2.4.4, 2.4.3, 2.4.2, 2.4.1, 2.4.0 | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | apache2 | 2.4.46-6 | — |
| Debian 13 | apache2 | 2.4.46-6 | — |
| Debian 12 | apache2 | 2.4.46-6 | — |
| Debian 10 | apache2 | 2.4.38-3+deb10u5 | DSA-4937-1 |
| Debian 9 | apache2 | 2.4.25-3+deb9u10 | DLA-2706-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 20.04 LTS | apache2 | 2.4.41-4ubuntu3.3 | USN-4994-1 |
| Ubuntu 18.04 LTS | apache2 | 2.4.29-1ubuntu4.16 | USN-4994-1 |
Show 2 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 16.04 LTS | apache2 | 2.4.18-2ubuntu3.17+esm1 | USN-4994-2 |
| Ubuntu Pro 14.04 LTS | apache2 | 2.4.7-1ubuntu4.22+esm1 | USN-4994-2 |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 8 | httpd +6 | 2.4.37-41.module+el8.5.0+11772+c8e0c271 | RHSA-2021:4257 |
| RHEL 8 | mod_http2 | 1.15.7-3.module+el8.4.0+8625+d397f3da | RHSA-2021:4257 |
| RHEL 8 | mod_md | 1:2.0.8-8.module+el8.3.0+6814+67d1e611 | RHSA-2021:4257 |
| RHEL 8 | mod_ssl +1 | 1:2.4.37-41.module+el8.5.0+11772+c8e0c271 | RHSA-2021:4257 |
Show 1 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Red Hat JBoss Core Services 1 | jbcs-httpd24-apr +1 | 1.6.3-107.el8jbcs | RHSA-2021:4614 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-apr-util +8 | 1.6.1-84.el8jbcs | RHSA-2021:4614 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-curl +2 | 7.78.0-2.el8jbcs | RHSA-2021:4614 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-httpd +6 | 2.4.37-78.el8jbcs | RHSA-2021:4614 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-mod_cluster-native | 1.3.16-9.Final_redhat_2.el8jbcs | RHSA-2021:4614 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-mod_http2 | 1.15.7-21.el8jbcs | RHSA-2021:4614 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-mod_jk +2 | 1.2.48-20.redhat_1.el8jbcs | RHSA-2021:4614 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-mod_md | 1:2.0.8-40.el8jbcs | RHSA-2021:4614 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-mod_security | 2.9.2-67.GA.el8jbcs | RHSA-2021:4614 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-mod_ssl +1 | 1:2.4.37-78.el8jbcs | RHSA-2021:4614 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-nghttp2 +1 | 1.39.2-39.el8jbcs | RHSA-2021:4614 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-openssl +4 | 1:1.1.1g-8.el8jbcs | RHSA-2021:4614 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-openssl-chil | 1.0.0-7.el8jbcs | RHSA-2021:4614 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-openssl-pkcs11 | 0.4.10-22.el8jbcs | RHSA-2021:4614 |
AlmaLinux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux 8 | mod_http2 | 1.15.7-3.module_el8.5.0+2609+b30d9eec | ALSA-2021:4257 |
| AlmaLinux 8 | mod_md | 1:2.0.8-8.module_el8.5.0+2609+b30d9eec | ALSA-2021:4257 |
Rocky Linux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Rocky Linux 8 | httpd | 2.4.37-41.module+el8.5.0+695+1fa8055e | RLSA-2021:4257 |
| Rocky Linux 8 | mod_http2 | 1.15.7-3.module+el8.4.0+553+7a69454b | RLSA-2021:4257 |
| Rocky Linux 8 | mod_md | 1:2.0.8-8.module+el8.4.0+553+7a69454b | RLSA-2021:4257 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP3 | apache2 | 2.4.43-3.22.1 | SUSE-SU-2021:2127-1 |
| SLES 15 SP2 | apache2 | 2.4.43-3.22.1 | SUSE-SU-2021:2127-1 |
| SLES 15 SP1 | apache2 | 2.4.33-3.50.1 | SUSE-SU-2021:2004-1 |
| SLES 15 | apache2 | 2.4.33-3.50.1 | SUSE-SU-2021:2004-1 |
| SLES 12 SP5 | apache2 | 2.4.23-29.74.1 | SUSE-SU-2021:2006-1 |
Show 19 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 12 SP4 | apache2 | 2.4.23-29.74.1 | SUSE-SU-2021:2006-1 |
| SLES 12 SP3 | apache2 | 2.4.23-29.74.1 | SUSE-SU-2021:2006-1 |
| SLES 12 SP2 | apache2 | 2.4.23-29.74.1 | SUSE-SU-2021:2006-1 |
| SLES for SAP 15 SP1 | apache2 | 2.4.33-3.50.1 | SUSE-SU-2021:2004-1 |
| SLES for SAP 15 | apache2 | 2.4.33-3.50.1 | SUSE-SU-2021:2004-1 |
| SLES for SAP 12 SP5 | apache2 | 2.4.23-29.74.1 | SUSE-SU-2021:2006-1 |
| SLES for SAP 12 SP4 | apache2 | 2.4.23-29.74.1 | SUSE-SU-2021:2006-1 |
| SLES for SAP 12 SP3 | apache2 | 2.4.23-29.74.1 | SUSE-SU-2021:2006-1 |
| SLE HPC 15 SP1 | apache2 | 2.4.33-3.50.1 | SUSE-SU-2021:2004-1 |
| SLE HPC 15 | apache2 | 2.4.33-3.50.1 | SUSE-SU-2021:2004-1 |
| SUSE OpenStack Cloud Crowbar 9 | apache2 | 2.4.23-29.74.1 | SUSE-SU-2021:2006-1 |
| SUSE OpenStack Cloud Crowbar 8 | apache2 | 2.4.23-29.74.1 | SUSE-SU-2021:2006-1 |
| SUSE OpenStack Cloud 9 | apache2 | 2.4.23-29.74.1 | SUSE-SU-2021:2006-1 |
| SUSE OpenStack Cloud 8 | apache2 | 2.4.23-29.74.1 | SUSE-SU-2021:2006-1 |
| SUSE Manager Server 4.0 | apache2 | 2.4.33-3.50.1 | SUSE-SU-2021:2004-1 |
| SUSE Manager Retail Branch Server 4.0 | apache2 | 2.4.33-3.50.1 | SUSE-SU-2021:2004-1 |
| SUSE Manager Proxy 4.0 | apache2 | 2.4.33-3.50.1 | SUSE-SU-2021:2004-1 |
| SUSE HPE Helion OpenStack 8 | apache2 | 2.4.23-29.74.1 | SUSE-SU-2021:2006-1 |
| SUSE Enterprise Storage 6 | apache2 | 2.4.33-3.50.1 | SUSE-SU-2021:2004-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Leap 15.3 | apache2 | 2.4.43-3.22.1 | openSUSE-SU-2021:2127-1 |
| openSUSE Leap 15.2 | apache2 | 2.4.43-lp152.2.15.1 | openSUSE-SU-2021:0908-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.24 | apache2 | 2.4.48-r0 | — |
| Alpine v3.23 | apache2 | 2.4.48-r0 | — |
| Alpine v3.22 | apache2 | 2.4.48-r0 | — |
| Alpine v3.21 | apache2 | 2.4.48-r0 | — |
| Alpine v3.20 | apache2 | 2.4.48-r0 | — |
Show 10 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.19 | apache2 | 2.4.48-r0 | — |
| Alpine v3.18 | apache2 | 2.4.48-r0 | — |
| Alpine v3.17 | apache2 | 2.4.48-r0 | — |
| Alpine v3.16 | apache2 | 2.4.48-r0 | — |
| Alpine v3.15 | apache2 | 2.4.48-r0 | — |
| Alpine v3.14 | apache2 | 2.4.48-r0 | — |
| Alpine v3.13 | apache2 | 2.4.48-r0 | — |
| Alpine v3.12 | apache2 | 2.4.48-r0 | — |
| Alpine v3.11 | apache2 | 2.4.48-r0 | — |
| Alpine v3.10 | apache2 | 2.4.48-r0 | — |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2 | httpd +7 | 2.4.48-2.amzn2 | ALAS2-2021-1674 |
| Amazon Linux 2 | mod_ssl +1 | 1:2.4.48-2.amzn2 | ALAS2-2021-1674 |
Azure Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Azure Linux 2 (CBL-Mariner) | httpd | 2.4.46-10 | — |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 8 | httpd +6 | 2.4.37-39.0.2.module+el8.4.0+20402+038b8ccd.1 | ELSA-2021-9545, ELSA-2021-4257 |
| Oracle Linux 8 | mod_http2 | 1.15.7-3.module+el8.4.0+20024+b87b2deb | ELSA-2021-9545, ELSA-2021-4257 |
| Oracle Linux 8 | mod_md | 1:2.0.8-8.module+el8.3.0+7816+49791cfd | ELSA-2021-9545, ELSA-2021-4257 |
| Oracle Linux 8 | mod_ssl +1 | 1:2.4.37-39.0.2.module+el8.4.0+20402+038b8ccd.1 | ELSA-2021-9545, ELSA-2021-4257 |
| Oracle Linux 7 | httpd +5 | 2.4.6-97.0.3.el7_9.1 | ELSA-2021-9541 |
| Oracle Linux 7 | mod_ssl +1 | 1:2.4.6-97.0.3.el7_9.1 | ELSA-2021-9541 |
Public exploits
Exploit or proof-of-concept code for this vulnerability is publicly available, which lowers the bar for attackers. Treat it as a reason to patch sooner.
Third-party code, not reviewed by us. Public PoCs are sometimes fake or contain malware. Read the code first and run it only in an isolated lab, against systems you are authorised to test.
GitHub 2 repositories
-
7own/CVE-2021-26690---Apache-mod_session ★ 1 · Nov 1, 2024
CVE-2021-26690 patch diffing - Apache HTTP mod_session NULL pointer dereference
-
danielduan2002/CVE-2021-26690 ★ 0 · Dec 27, 2024
Sources: PoC-in-GitHub, Metasploit Framework, Exploit-DB — updated daily. Only links are listed; no exploit code is hosted here.
Advisories 19
- ALSA-2021:4257 Moderate: httpd:2.4 security, bug fix, and enhancement update AlmaLinux Security Advisories · Oct 29, 2026
- RHSA-2021:4614 Red Hat Security Advisory: Red Hat JBoss Core Services Apache HTTP Server 2.4.37 SP10 security update Red Hat Security Advisories (RHSA) · Oct 9, 2026
- RHSA-2021:4257 Red Hat Security Advisory: httpd:2.4 security, bug fix, and enhancement update Red Hat Security Advisories (RHSA) · Sep 21, 2026
- USN-4994-2 apache2 vulnerabilities Ubuntu Security Notices (USN) · Jun 29, 2026
- USN-4994-1 apache2 vulnerabilities Ubuntu Security Notices (USN) · Apr 22, 2026
- DSA-4937-1 apache2 - security update Debian Security (DSA / DLA) · Mar 9, 2026
- DLA-2706-1 apache2 - security update Debian Security (DSA / DLA) · Mar 9, 2026
- RLSA-2021:4257 Moderate: httpd:2.4 security, bug fix, and enhancement update Rocky Linux Security Advisories · Feb 4, 2026
- SUSE-SU-2021:2004-1 Security update for apache2 SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2021:0908-1 Security update for apache2 SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2021:2127-1 Security update for apache2 SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2021:2127-1 Security update for apache2 SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2021:2006-1 Security update for apache2 SUSE / openSUSE Security Updates · Feb 4, 2026
- WID-SEC-2024-1591 Juniper JUNOS: Mehrere Schwachstellen BSI CERT-Bund (WID) · Nov 11, 2024
- WID-SEC-2022-0438 Apache HTTP Server: Mehrere Schwachstellen BSI CERT-Bund (WID) · May 26, 2024
- ELSA-2021-4257 Moderate: httpd:2.4 security, bug fix, and enhancement update (Oracle Linux 8) Oracle Linux Security Advisories (ELSA) · Nov 16, 2021
- ELSA-2021-9545 Important: httpd:2.4 security update (Oracle Linux 8) Oracle Linux Security Advisories (ELSA) · Nov 11, 2021
- ELSA-2021-9541 Important: httpd security update (Oracle Linux 7) Oracle Linux Security Advisories (ELSA) · Nov 4, 2021
- ALAS2-2021-1674 Moderate: httpd security update (Amazon Linux 2) Amazon Linux Security Center (ALAS) · Jul 1, 2021
References
- http://httpd.apache.org/security/vulnerabilities_24.html
- https://lists.apache.org/thread.html/re026d3da9d7824bd93b9f871c0fdda978d960c7e62d8c43cba8d0bf3%40%3Ccvs.httpd.apache.org%3E
- [httpd-announce] 20210609 CVE-2021-26690: mod_session NULL pointer dereference mailing-list
- [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.jso mailing-list
- [oss-security] 20210609 CVE-2021-26690: Apache httpd: mod_session NULL pointer dereference mailing-list
- [debian-lts-announce] 20210709 [SECURITY] [DLA 2706-1] apache2 security update mailing-list
- DSA-4937 vendor-advisory
- GLSA-202107-38 vendor-advisory
- FEDORA-2021-dce7e7738e vendor-advisory
- FEDORA-2021-e3f6dd670d vendor-advisory
- https://www.oracle.com/security-alerts/cpuoct2021.html
- https://security.netapp.com/advisory/ntap-20210702-0001/