dbcve.org
HTTP ServerWeb server / proxy · Apache

CVE-2023-27522

HIGH · 7.5 CVSS v3.1 Published 2023-03-07
Fix available
A fix is available. Upgrade to 2.0.22 / 2.4.56 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
HTTP Response Smuggling vulnerability in Apache HTTP Server via mod_proxy_uwsgi. This issue affects Apache HTTP Server: from 2.4.30 through 2.4.55. Special characters in the origin response header can truncate/split the response forwarded to the client.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

HTTP Response Smuggling vulnerability in Apache HTTP Server's mod_proxy_uwsgi module where special characters in the origin response header can cause the response forwarded to clients to be truncated or split, potentially allowing cache poisoning or response manipulation attacks.

MitigationUpgrade Apache HTTP Server to version 2.4.56 or later which contains the fix for this vulnerability in mod_proxy_uwsgi.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
HTTP ServerWeb server / proxy
Affected:>= 2.4.30, < 2.4.56
Debian LinuxOperating system
Affected:= 10.0
UwsgiApplication
Affected:< 2.0.22

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check Apache HTTP Server version
    Run 'apache2 -v' or 'httpd -v' to determine the installed Apache version
    Affected if Version is >= 2.4.30 and < 2.4.56
  2. Verify mod_proxy_uwsgi module is loaded
    Run 'apache2ctl -M' or 'httpd -M' and look for 'proxy_uwsgi_module' in the loaded modules list
    Affected if mod_proxy_uwsgi is listed as loaded
  3. Check for active proxy_uwsgi configuration
    Inspect Apache configuration files for 'ProxyPass' or 'ProxyPassMatch' directives using 'uwsgi://' protocol, or check for 'ProxyUwsgiPass' directives
    Affected if A proxy rule forwarding to a uwsgi backend is configured and active
  4. Check Unbit Uwsgi version if used
    Run 'uwsgi --version' to determine the installed UwSGI version if mod_proxy_uwsgi forwards to a UwSGI backend
    Affected if UwSGI version is < 2.0.22 and is used as a backend for Apache

You are affected if Apache HTTP Server version is between 2.4.30 and 2.4.56 inclusive, mod_proxy_uwsgi is loaded, and a uwsgi:// proxy configuration is actively in use

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 2.0.22 / 2.4.56 or later
Fixed in 2.0.222.4.56
Interim mitigation

Upgrade Apache HTTP Server to version 2.4.56 or later which contains the fix for this vulnerability in mod_proxy_uwsgi.

Recommended fix High confidence

Apache HTTP Server 2.4.56 or later

  1. Identify the current Apache HTTP Server version using 'httpd -v' or 'apache2 -v'
  2. Stop the Apache HTTP Server service using 'systemctl stop apache2' (Debian) or 'systemctl stop httpd' (RHEL-based)
  3. Update the package manager repository metadata
  4. Install Apache HTTP Server version 2.4.56 or later using the appropriate package manager (apt-get install apache2 for Debian, yum install httpd for RHEL)
  5. Verify the installed version is 2.4.56 or higher using 'httpd -v'
  6. Start the Apache HTTP Server service using 'systemctl start apache2' or 'systemctl start httpd'
  7. Test that the mod_proxy_uwsgi functionality works correctly with a test application
Caveat Standard Apache upgrade - review release notes for module compatibility changes; test in staging environment before production deployment

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in HTTP Server Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA1.0 h
10.0 hours of engineering $1,750
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,800.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2023-27522 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data