Description
A carefully crafted If: request header can cause a memory read, or write of a single zero byte, in a pool (heap) memory location beyond the header value sent. This could cause the process to crash.
This issue affects Apache HTTP Server 2.4.54 and earlier.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Apache Software Foundation | Apache HTTP Server | 2.4 – ≤ 2.4.54 | — |
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 | 2.4.55-1 | — |
| Debian 13 | apache2 | 2.4.55-1 | — |
| Debian 12 | apache2 | 2.4.55-1 | — |
| Debian 11 | apache2 | 2.4.56-1~deb11u1 | DSA-5376-1 |
| Debian 10 | apache2 | 2.4.38-3+deb10u9 | DLA-3351-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 22.04 LTS | apache2 | 2.4.52-1ubuntu4.3 | USN-5839-1 |
| Ubuntu 20.04 LTS | apache2 | 2.4.41-4ubuntu3.13 | USN-5839-1 |
| Ubuntu 18.04 LTS | apache2 | 2.4.29-1ubuntu4.26 | USN-5839-1 |
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+esm8 | USN-5834-1 |
| Ubuntu Pro 14.04 LTS | apache2 | No fix yet | — |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 9 | httpd +8 | 2.4.53-7.el9_1.1 | RHSA-2023:0970 |
| RHEL 9 | mod_ssl +1 | 1:2.4.53-7.el9_1.1 | RHSA-2023:0970 |
| RHEL 8 | httpd +6 | 2.4.37-51.module+el8.7.0+18026+7b169787.1 | RHSA-2023:0852 |
| RHEL 8 | mod_http2 | 1.15.7-5.module+el8.6.0+13996+01710940 | RHSA-2023:0852 |
| RHEL 8 | mod_md | 1:2.0.8-8.module+el8.3.0+6814+67d1e611 | RHSA-2023:0852 |
| RHEL 8 | mod_ssl +1 | 1:2.4.37-51.module+el8.7.0+18026+7b169787.1 | RHSA-2023:0852 |
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-util +8 | 1.6.1-101.el7jbcs | RHSA-2023:3354 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-curl +2 | 8.0.1-1.el7jbcs | RHSA-2023:3354 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-httpd +6 | 2.4.51-39.el7jbcs | RHSA-2023:3354 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-mod_ssl +1 | 1:2.4.51-39.el7jbcs | RHSA-2023:3354 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-openssl +4 | 1:1.1.1k-14.el7jbcs | RHSA-2023:3354 |
AlmaLinux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux 9 | httpd +8 | 2.4.53-7.el9_1.1 | ALSA-2023:0970 |
| AlmaLinux 9 | mod_ssl +1 | 1:2.4.53-7.el9_1.1 | ALSA-2023:0970 |
| AlmaLinux 8 | httpd +6 | 2.4.37-51.module_el8.7.0+3405+9516b832.1 | ALSA-2023:0852 |
| AlmaLinux 8 | mod_http2 | 1.15.7-5.module_el8.6.0+2872+fe0ff7aa | ALSA-2023:0852 |
| AlmaLinux 8 | mod_md | 1:2.0.8-8.module_el8.6.0+2872+fe0ff7aa | ALSA-2023:0852 |
| AlmaLinux 8 | mod_ssl +1 | 1:2.4.37-51.module_el8.7.0+3405+9516b832.1 | ALSA-2023:0852 |
Rocky Linux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Rocky Linux 9 | httpd | 2.4.53-7.el9_1.1 | RLSA-2023:0970 |
| Rocky Linux 8 | httpd | 2.4.37-51.module+el8.7.0+1059+126e9251 | RLSA-2023:0852 |
| Rocky Linux 8 | mod_http2 | 1.15.7-5.module+el8.6.0+823+f143cee1 | RLSA-2023:0852 |
| Rocky Linux 8 | mod_md | 1:2.0.8-8.module+el8.5.0+695+1fa8055e | RLSA-2023:0852 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP5 | apache2 | 2.4.66-150400.6.57.1 | SUSE-SU-2026:2686-1 |
| SLES 15 SP4 | apache2 | 2.4.51-150400.6.6.1 | SUSE-SU-2026:2686-1, SUSE-SU-2023:0322-1 |
| SLES 15 SP3 | apache2 | 2.4.51-150200.3.51.1 | SUSE-SU-2023:0321-1 |
| SLES 15 SP2 | apache2 | 2.4.51-150200.3.51.1 | SUSE-SU-2023:0321-1 |
| SLES 15 SP1 | apache2 | 2.4.33-150000.3.72.1 | SUSE-SU-2023:0294-1 |
Show 24 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 12 SP5 | apache2 | 2.4.51-35.22.1 | SUSE-SU-2023:0185-1 |
| SLES 12 SP4 | apache2 | 2.4.23-29.94.1 | SUSE-SU-2023:0183-1 |
| SLES 12 SP2 | apache2 | 2.4.23-29.94.1 | SUSE-SU-2023:0183-1 |
| SLES for SAP 15 SP5 | apache2 | 2.4.66-150400.6.57.1 | SUSE-SU-2026:2686-1 |
| SLES for SAP 15 SP4 | apache2 | 2.4.66-150400.6.57.1 | SUSE-SU-2026:2686-1 |
| SLES for SAP 15 SP3 | apache2 | 2.4.51-150200.3.51.1 | SUSE-SU-2023:0321-1 |
| SLES for SAP 15 SP2 | apache2 | 2.4.51-150200.3.51.1 | SUSE-SU-2023:0321-1 |
| SLES for SAP 15 SP1 | apache2 | 2.4.33-150000.3.72.1 | SUSE-SU-2023:0294-1 |
| SLES for SAP 12 SP5 | apache2 | 2.4.51-35.22.1 | SUSE-SU-2023:0185-1 |
| SLES for SAP 12 SP4 | apache2 | 2.4.23-29.94.1 | SUSE-SU-2023:0183-1 |
| SLE Real Time 15 SP3 | apache2 | 2.4.51-150200.3.51.1 | SUSE-SU-2023:0321-1 |
| SLE HPC 15 SP5 | apache2 | 2.4.66-150400.6.57.1 | SUSE-SU-2026:2686-1 |
| SLE HPC 15 SP4 | apache2 | 2.4.66-150400.6.57.1 | SUSE-SU-2026:2686-1 |
| SLE HPC 15 SP3 | apache2 | 2.4.51-150200.3.51.1 | SUSE-SU-2023:0321-1 |
| SLE HPC 15 SP2 | apache2 | 2.4.51-150200.3.51.1 | SUSE-SU-2023:0321-1 |
| SLE HPC 15 SP1 | apache2 | 2.4.33-150000.3.72.1 | SUSE-SU-2023:0294-1 |
| SUSE OpenStack Cloud Crowbar 9 | apache2 | 2.4.23-29.94.1 | SUSE-SU-2023:0183-1 |
| SUSE OpenStack Cloud 9 | apache2 | 2.4.23-29.94.1 | SUSE-SU-2023:0183-1 |
| SUSE Manager Server 4.2 | apache2 | 2.4.51-150200.3.51.1 | SUSE-SU-2023:0321-1 |
| SUSE Manager Retail Branch Server 4.2 | apache2 | 2.4.51-150200.3.51.1 | SUSE-SU-2023:0321-1 |
| SUSE Manager Proxy 4.2 | apache2 | 2.4.51-150200.3.51.1 | SUSE-SU-2023:0321-1 |
| SUSE Enterprise Storage 7.1 | apache2 | 2.4.51-150200.3.51.1 | SUSE-SU-2023:0321-1 |
| SUSE Enterprise Storage 7 | apache2 | 2.4.51-150200.3.51.1 | SUSE-SU-2023:0321-1 |
| SUSE Enterprise Storage 6 | apache2 | 2.4.33-150000.3.72.1 | SUSE-SU-2023:0294-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | apache2 | 2.4.55-1.1 | openSUSE-SU-2024:12635-1 |
| openSUSE Leap 15.4 | apache2 | 2.4.51-150400.6.6.1 | SUSE-SU-2023:0322-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.17 | apache2 | 2.4.55-r0 | — |
| Alpine v3.16 | apache2 | 2.4.55-r0 | — |
| Alpine v3.15 | apache2 | 2.4.55-r0 | — |
| Alpine v3.14 | apache2 | 2.4.55-r0 | — |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2023 | httpd +8 | 2.4.55-1.amzn2023 | ALAS2023-2023-115 |
| Amazon Linux 2023 | mod_ssl +1 | 1:2.4.55-1.amzn2023 | ALAS2023-2023-115 |
| Amazon Linux 2 | httpd +7 | 2.4.55-1.amzn2 | ALAS2-2023-1938 |
| Amazon Linux 2 | mod_ssl +1 | 1:2.4.55-1.amzn2 | ALAS2-2023-1938 |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 9 | httpd +8 | 2.4.53-7.0.1.el9_1.1 | ELSA-2023-0970 |
| Oracle Linux 9 | mod_ssl +1 | 1:2.4.53-7.0.1.el9_1.1 | ELSA-2023-0970 |
| Oracle Linux 8 | httpd +6 | 2.4.37-51.0.1.module+el8.7.0+20923+af3b70dd.1 | ELSA-2023-0852 |
| Oracle Linux 8 | mod_http2 | 1.15.7-5.module+el8.6.0+20548+01710940 | ELSA-2023-0852 |
| Oracle Linux 8 | mod_md | 1:2.0.8-8.module+el8.5.0+20475+4f6a8fd5 | ELSA-2023-0852 |
| Oracle Linux 8 | mod_ssl +1 | 1:2.4.37-51.0.1.module+el8.7.0+20923+af3b70dd.1 | ELSA-2023-0852 |
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 1 repository
-
r1az4r/CVE-2006-20001 ★ 0 · Feb 7, 2023
A carefully crafted If: request header can cause a memory read, or write of a single zero byte, in a pool (heap) memory location beyond the header value sent. This could cause the process to crash. T…
Sources: PoC-in-GitHub, Metasploit Framework, Exploit-DB — updated daily. Only links are listed; no exploit code is hosted here.
Advisories 32
- ALSA-2023:0852 Moderate: httpd:2.4 security and bug fix update AlmaLinux Security Advisories · Nov 5, 2026
- ALSA-2023:0970 Moderate: httpd security and bug fix update AlmaLinux Security Advisories · Oct 29, 2026
- RHSA-2023:3354 Red Hat Security Advisory: Red Hat JBoss Core Services Apache HTTP Server 2.4.51 SP2 security update Red Hat Security Advisories (RHSA) · Oct 15, 2026
- RHSA-2023:0970 Red Hat Security Advisory: httpd security and bug fix update Red Hat Security Advisories (RHSA) · Sep 21, 2026
- RHSA-2023:0852 Red Hat Security Advisory: httpd:2.4 security and bug fix update Red Hat Security Advisories (RHSA) · Sep 21, 2026
- SUSE-SU-2026:2686-1 Security update for apache2 SUSE / openSUSE Security Updates · Jul 1, 2026
- WID-SEC-2023-0110 Apache HTTP Server: Mehrere Schwachstellen BSI CERT-Bund (WID) · Jun 30, 2026
- USN-5834-1 apache2 vulnerabilities Ubuntu Security Notices (USN) · Jun 25, 2026
- USN-5839-1 apache2 vulnerabilities Ubuntu Security Notices (USN) · Apr 27, 2026
- DSA-5376-1 apache2 - security update Debian Security (DSA / DLA) · Mar 9, 2026
- DLA-3351-1 apache2 - security update Debian Security (DSA / DLA) · Mar 9, 2026
- RLSA-2023:0852 Moderate: httpd:2.4 security and bug fix update Rocky Linux Security Advisories · Feb 5, 2026
- RLSA-2023:0970 Moderate: httpd security and bug fix update Rocky Linux Security Advisories · Feb 4, 2026
- SUSE-SU-2023:0183-1 Security update for apache2 SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2023:0294-1 Security update for apache2 SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2023:0322-1 Security update for apache2 SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2024:12635-1 apache2-2.4.55-1.1 on GA media SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2023:0185-1 Security update for apache2 SUSE / openSUSE Security Updates · Feb 4, 2026
- FSA-202302 Festo: Several vulnerabilities in FactoryViews CERT@VDE · Feb 2, 2026
- ICSA-26-027-02 Festo Didactic SE MES PC CISA ICS & IT advisories · Jan 27, 2026
- FSA-202402 Several Vulnerabilities in MES PC (Windows 10) CERT@VDE · Dec 8, 2025
- WID-SEC-2023-1424 Xerox FreeFlow Print Server für Solaris: Mehrere Schwachstellen BSI CERT-Bund (WID) · Oct 6, 2025
- SUSE-SU-2023:0321-1 Security update for apache2 SUSE / openSUSE Security Updates · May 2, 2025
- ICSA-25-133-01 Hitachi Energy Service Suite CISA ICS & IT advisories · Feb 25, 2025
- WID-SEC-2024-1591 Juniper JUNOS: Mehrere Schwachstellen BSI CERT-Bund (WID) · Nov 11, 2024
- SSA-806742 SSA-806742: Multiple Vulnerabilities in SCALANCE XCM-/XRM-300 before V2.4 Siemens ProductCERT · Feb 13, 2024
- ICSA-24-046-11 Siemens SCALANCE XCM-/XRM-300 CISA ICS & IT advisories · Feb 13, 2024
- WID-SEC-2023-0561 Xerox FreeFlow Print Server: Mehrere Schwachstellen BSI CERT-Bund (WID) · May 18, 2023
- ALAS2023-2023-115 Important: httpd security update (Amazon Linux 2023) Amazon Linux Security Center (ALAS) · Mar 8, 2023
- ELSA-2023-0970 Moderate: httpd security and bug fix update (Oracle Linux 9) Oracle Linux Security Advisories (ELSA) · Feb 28, 2023
- ALAS2-2023-1938 Important: httpd security update (Amazon Linux 2) Amazon Linux Security Center (ALAS) · Feb 22, 2023
- ELSA-2023-0852 Moderate: httpd:2.4 security and bug fix update (Oracle Linux 8) Oracle Linux Security Advisories (ELSA) · Feb 22, 2023