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Public proof of conceptFix available

CVE-2006-20001

A public proof of concept exists; no exploitation attested.

  • Published2023-01-17
  • Fixed in2.4.55
  • WeaknessCWE-787

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

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.

Timeline

dates in UTC
  1. 2023-01-1720:15CVE publishedNVD
  2. 2026-10-2319:23First public proof of conceptPoC-in-GitHub

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2006-20001?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2006-20001?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD
Apache HTTP Server
BranchAffectedFixed in
2.4< 2.4.552.4.55

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • httpdAlmaLinux:9all versions · fixed in 2.4.53-7.el9_1.1and 8 other packages
  • httpdAlmaLinux:8all versions · fixed in 2.4.37-51.module_el8.7.0+3405+9516b832.1and 6 other packages
  • mod_http2AlmaLinux:8all versions · fixed in 1.15.7-5.module_el8.6.0+2872+fe0ff7aa
  • mod_http2AlmaLinux:8all versions · fixed in 1.15.7-5.module_el8.6.0+3031+fb177b09
  • mod_mdAlmaLinux:8all versions · fixed in 1:2.0.8-8.module_el8.6.0+2872+fe0ff7aa
  • mod_mdAlmaLinux:8all versions · fixed in 1:2.0.8-8.module_el8.6.0+3031+fb177b09
  • mod_sslAlmaLinux:9all versions · fixed in 1:2.4.53-7.el9_1.1and 1 other package
  • mod_sslAlmaLinux:8all versions · fixed in 1:2.4.37-51.module_el8.7.0+3405+9516b832.1and 1 other package

Full record on NVD

Fix

  1. Update Apache HTTP Server to 2.4.55

Advisories and patches

Detection

read 2026-10-23 19:23 UTC
Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
1 repository, unverifiedr1az4r/CVE-2006-20001
PoC-in-GitHub

Sources

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Published
2023-01-17
Last Modified
2026-06-16
NVD status
Modified

Frequently asked questions

What is CVE-2006-20001?

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.

Is CVE-2006-20001 actively exploited?

Active exploitation of CVE-2006-20001 has not been confirmed. Its EPSS score was 3.5% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2006-20001?

CVE-2006-20001 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

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