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NVD / CVE Program· CNA apache

CVE-2026-43951: Apache HTTP Server: OOB Read in `merge_response_headers` can cause crash

MediumCVSS 6.5 · v3.1—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 26/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.54% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • According to CISA the attack is automatable: targets can be found by mass scanning.
  • Fixed version: httpd (AlmaLinux:10) 2.4.63-13.el10_2.4; httpd-core (AlmaLinux:10) 2.4.63-13.el10_2.4; httpd-devel (AlmaLinux:10) 2.4.63-13.el10_2.4.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to httpd (AlmaLinux:10) 2.4.63-13.el10_2.4; httpd-core (AlmaLinux:10) 2.4.63-13.el10_2.4; httpd-devel (AlmaLinux:10) 2.4.63-13.el10_2.4 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

Out-of-bounds Read vulnerability in Apache HTTP Server with mod_headers and mod_mime and multiple response languages. This issue affects Apache HTTP Server: from 2.4.0 through 2.4.67.

Published
Jun 8, 2026
Updated
Jul 23, 2026
EPSS
0.5% · 46th percentile

Report tools

JSON

Action score

26

Monitor

Low priority for now.

CVSS
26 / 40 · 6.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.5%

CISA SSVC decision

Exploitation
none
Automatable
yes
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2026-43951

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

One daily email digest (06:00 UTC); connect a webhook for KEV listings and weaponized exploits every 10 minutes on paid plans, on the hour on the free plan.

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
apachehttp server

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When you'll hear from us

  • when a new CVE affecting this product is published
  • when a record in your stack enters KEV or is weaponized

One daily email digest (06:00 UTC); connect a webhook for KEV listings and weaponized exploits every 10 minutes on paid plans, on the hour on the free plan.

Is Apache HTTP Server on your server exposed to the internet?Run a port scan

Your free account also gets you

  • CVE alerts: add the products and versions you run, get the new CVEs that affect them
  • Uptime monitoring: 1 site, instant email when it goes down
  • Add your domain: subdomains and takeover risk scanned every week (1 domain)
  • 10 scans an hour on the security tools, at most 30 a day (3 a day without an account), an API key and MCP
  • All your scans in one panel: findings, what changed in the last scan, a report per domain or per client (PDF, share link)
All free tools

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Free account, no card. Unfollow any time.

Don't want an account? Get "Exploited this week" by email every Monday

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Versions reported by the vendor

Affected version ranges reported by the assigning authority (apache). Independent of NVD's CPE analysis and usually ahead of it.

  • Apache Software Foundation Apache HTTP Server

    • 2.4.0 and later · up to and including 2.4.67affected · semver

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • apache http server2.4.0 and later · up to 2.4.67 inclusive

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
AlmaLinux:10httpdbefore 2.4.63-13.el10_2.42.4.63-13.el10_2.4
AlmaLinux:10httpd-corebefore 2.4.63-13.el10_2.42.4.63-13.el10_2.4
AlmaLinux:10httpd-develbefore 2.4.63-13.el10_2.42.4.63-13.el10_2.4
AlmaLinux:10httpd-filesystembefore 2.4.63-13.el10_2.42.4.63-13.el10_2.4
AlmaLinux:10httpd-manualbefore 2.4.63-13.el10_2.42.4.63-13.el10_2.4
AlmaLinux:10httpd-toolsbefore 2.4.63-13.el10_2.42.4.63-13.el10_2.4
AlmaLinux:10mod_http2before 2.0.29-4.el10_2.22.0.29-4.el10_2.2
AlmaLinux:10mod_ldapbefore 2.4.63-13.el10_2.42.4.63-13.el10_2.4
AlmaLinux:10mod_luabefore 2.4.63-13.el10_2.42.4.63-13.el10_2.4
AlmaLinux:10mod_proxy_htmlbefore 1:2.4.63-13.el10_2.41:2.4.63-13.el10_2.4
AlmaLinux:10mod_sessionbefore 2.4.63-13.el10_2.42.4.63-13.el10_2.4
AlmaLinux:10mod_sslbefore 1:2.4.63-13.el10_2.41:2.4.63-13.el10_2.4
AlmaLinux:8httpdbefore 2.4.37-65.module_el8.10.0+4233+8b7d9181.92.4.37-65.module_el8.10.0+4233+8b7d9181.9
AlmaLinux:8httpd-develbefore 2.4.37-65.module_el8.10.0+4233+8b7d9181.92.4.37-65.module_el8.10.0+4233+8b7d9181.9
AlmaLinux:8httpd-manualbefore 2.4.37-65.module_el8.10.0+4233+8b7d9181.92.4.37-65.module_el8.10.0+4233+8b7d9181.9
AlmaLinux:8httpd-toolsbefore 2.4.37-65.module_el8.10.0+4233+8b7d9181.92.4.37-65.module_el8.10.0+4233+8b7d9181.9
AlmaLinux:8mod_http2before 1.15.7-10.module_el8.10.0+4233+8b7d9181.71.15.7-10.module_el8.10.0+4233+8b7d9181.7
AlmaLinux:8mod_ldapbefore 2.4.37-65.module_el8.10.0+4233+8b7d9181.92.4.37-65.module_el8.10.0+4233+8b7d9181.9
AlmaLinux:8mod_mdbefore 1:2.0.8-8.module_el8.10.0+4088+57f011c1.21:2.0.8-8.module_el8.10.0+4088+57f011c1.2
AlmaLinux:8mod_proxy_htmlbefore 1:2.4.37-65.module_el8.10.0+4233+8b7d9181.91:2.4.37-65.module_el8.10.0+4233+8b7d9181.9
AlmaLinux:8mod_sessionbefore 2.4.37-65.module_el8.10.0+4233+8b7d9181.92.4.37-65.module_el8.10.0+4233+8b7d9181.9
AlmaLinux:8mod_sslbefore 1:2.4.37-65.module_el8.10.0+4233+8b7d9181.91:2.4.37-65.module_el8.10.0+4233+8b7d9181.9
AlmaLinux:9httpdbefore 2.4.62-13.el9_8.52.4.62-13.el9_8.5
AlmaLinux:9httpd-corebefore 2.4.62-13.el9_8.52.4.62-13.el9_8.5

+96

Same product

apache: all records

Other highest-scoring records for the same primary product.

  • CVE-2021-42013Path Traversal and Remote Code Execution in Apache HTTP Server 2.4.49 and 2.4.50 (incomplete fix of CVE-2021-41773)KEV
    99Now
  • CVE-2021-41773Path traversal and file disclosure vulnerability in Apache HTTP Server 2.4.49KEV
    99Now
  • CVE-2024-38475Apache HTTP Server weakness in mod_rewrite when first segment of substitution matches filesystem path.KEV
    96Now

Published before and after this one in the same product

  • ← EarlierCVE-2026-42535Jun 8, 2026 · Apache HTTP Server: mod_dav_fs protected directory access
    36Monitor
  • ← EarlierCVE-2026-42536Jun 8, 2026 · Apache HTTP Server: mod_xml2enc heap overflow
    30Monitor
  • Later →CVE-2026-44119Jun 8, 2026 · Apache HTTP Server: escalation of privilege through expressions in .htaccess in multiple modules
    22Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
almalinux:httpd2.4.62-13.el9_8.5 · AlmaLinux:9Package registry (OSV)
almalinux:httpd2.4.63-13.el10_2.4 · AlmaLinux:10Package registry (OSV)
almalinux:httpd-core2.4.62-13.el9_8.5 · AlmaLinux:9Package registry (OSV)
almalinux:httpd-core2.4.63-13.el10_2.4 · AlmaLinux:10Package registry (OSV)
almalinux:httpd-devel2.4.62-13.el9_8.5 · AlmaLinux:9Package registry (OSV)
almalinux:httpd-devel2.4.63-13.el10_2.4 · AlmaLinux:10Package registry (OSV)
almalinux:httpd-filesystem2.4.62-13.el9_8.5 · AlmaLinux:9Package registry (OSV)
almalinux:httpd-filesystem2.4.63-13.el10_2.4 · AlmaLinux:10Package registry (OSV)
almalinux:httpd-manual2.4.62-13.el9_8.5 · AlmaLinux:9Package registry (OSV)
almalinux:httpd-manual2.4.63-13.el10_2.4 · AlmaLinux:10Package registry (OSV)
almalinux:httpd-tools2.4.62-13.el9_8.5 · AlmaLinux:9Package registry (OSV)
almalinux:httpd-tools2.4.63-13.el10_2.4 · AlmaLinux:10Package registry (OSV)
almalinux:mod_http22.0.29-4.el10_2.2 · AlmaLinux:10Package registry (OSV)
almalinux:mod_ldap2.4.62-13.el9_8.5 · AlmaLinux:9Package registry (OSV)
almalinux:mod_ldap2.4.63-13.el10_2.4 · AlmaLinux:10Package registry (OSV)
almalinux:mod_lua2.4.62-13.el9_8.5 · AlmaLinux:9Package registry (OSV)
almalinux:mod_lua2.4.63-13.el10_2.4 · AlmaLinux:10Package registry (OSV)
almalinux:mod_proxy_html1:2.4.62-13.el9_8.5 · AlmaLinux:9Package registry (OSV)
almalinux:mod_proxy_html1:2.4.63-13.el10_2.4 · AlmaLinux:10Package registry (OSV)
almalinux:mod_session2.4.62-13.el9_8.5 · AlmaLinux:9Package registry (OSV)
almalinux:mod_session2.4.63-13.el10_2.4 · AlmaLinux:10Package registry (OSV)
almalinux:mod_ssl1:2.4.62-13.el9_8.5 · AlmaLinux:9Package registry (OSV)
almalinux:mod_ssl1:2.4.63-13.el10_2.4 · AlmaLinux:10Package registry (OSV)
alpine:apache22.4.68-r0 · Alpine:v3.21Package registry (OSV)
debian:apache22.4.68-1~deb12u1 · Debian:12Package registry (OSV)
opensuse:apache22.4.66-160000.3.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:apache2-devel2.4.66-160000.3.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:apache2-event2.4.66-160000.3.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:apache2-manual2.4.66-160000.3.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:apache2-prefork2.4.66-160000.3.1 · openSUSE:Leap 16.0Package registry (OSV)

+29

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-3385735 days apartApache HTTP Server: Off-by-one OOB reads in AJP getter functions
    21Monitor
  • CVE-2026-3403235 days apartApache HTTP Server: mod_proxy_ajp: Heap Buffer Over-Read Due to Missing Null-Termination Check (ajp_msg_get_string)
    21Monitor

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Not on record for this CVE: EPSS history · patch commit or PR link · public bounty program.

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
low · data can be read
Integrity
low · data or configuration can be modified
Availability
none
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
Low
Integrity impact
Low
Availability impact
None

Weakness class (CWE)

CWE-125 · Out-of-bounds Read

CVSS vector

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

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

References

Show all references (1 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records