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HTTP ServerWeb server / proxy · Apache

CVE-2024-47252

HIGH · 7.5 CVSS v3.1 Published 2025-07-10
Fix available
A fix is available. Upgrade to 2.4.64 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
Insufficient escaping of user-supplied data in mod_ssl in Apache HTTP Server 2.4.63 and earlier allows an untrusted SSL/TLS client to insert escape characters into log files in some configurations. In a logging configuration where CustomLog is used with "%{varname}x" or "%{varname}c" to log variables provided by mod_ssl such as SSL_TLS_SNI, no escaping is performed by either mod_log_config or mod_ssl and unsanitized data provided by the client may appear in log files.

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 · high confidence

Insufficient escaping of user-supplied SSL/TLS variables in mod_ssl allows an untrusted client to inject escape characters into Apache HTTP Server log files. When CustomLog uses %{varname}x or %{varname}c format strings (e.g., %{SSL_TLS_SNI}x) to log mod_ssl variables, the client-provided data is logged without sanitization by either mod_log_config or mod_ssl, enabling log injection attacks.

MitigationAvoid using %{SSL_TLS_SNI}x or similar client-supplied variables in CustomLog configurations until a patched version is available, or implement application-layer sanitization of logged SSL variables to prevent escape character injection.

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:>= 2.4.0, < 2.4.64

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
High
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/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 'httpd -v' or 'apache2 -v' to obtain the server version number
    Affected if Version is 2.4.0 or higher but lower than 2.4.64
  2. Verify mod_ssl is loaded
    Check for 'ssl_module' in the loaded modules list via 'httpd -M' or 'apache2ctl -M'
    Affected if mod_ssl module is loaded and in use
  3. Inspect CustomLog configuration for vulnerable format strings
    Search Apache configuration files (httpd.conf, ssl.conf, included files) for 'CustomLog' directives that contain '%{SSL_' or '%{TLS_' followed by 'x' or 'c' format specifiers (e.g., %{SSL_TLS_SNI}x, %{SSL_CLIENT_S_DN}c)
    Affected if CustomLog directive uses %{SSL_TLS_SNI}x or similar mod_ssl variable format strings in log definitions

You are affected if your Apache version is between 2.4.0 and 2.4.63 inclusive, mod_ssl is loaded, and CustomLog is configured to log SSL/TLS variables using %{varname}x or %{varname}c format strings.

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 2.4.64 or later
Fixed in 2.4.64
Interim mitigation

Avoid using %{SSL_TLS_SNI}x or similar client-supplied variables in CustomLog configurations until a patched version is available, or implement application-layer sanitization of logged SSL variables to prevent escape character injection.

Recommended fix High confidence

Apache HTTP Server 2.4.64 or later

  1. 1. Identify the current Apache HTTP Server version: `httpd -v` or `apache2 -v`
  2. 2. For Debian/Ubuntu: Update package lists with `sudo apt update`
  3. 3. For Debian/Ubuntu: Upgrade Apache2 with `sudo apt install apache2` to get the latest available version
  4. 4. For RHEL/CentOS: Update with `sudo yum update httpd` or `sudo dnf update httpd`
  5. 5. For other distributions: Obtain Apache HTTP Server 2.4.64 or later from apache.org or your vendor
  6. 6. After upgrade, verify the version is >= 2.4.64: `httpd -v`
  7. 7. Restart Apache to load the new version: `sudo systemctl restart apache2` (Debian/Ubuntu) or `sudo systemctl restart httpd` (RHEL/CentOS)
  8. 8. Review CustomLog configurations using SSL variables (%{SSL_TLS_SNI}x, %{SSL_TLS_SNI}c, etc.) to ensure logging behaves as expected after the upgrade
Caveat Minor: Ensure any custom log parsing scripts handle any new escaping that may be applied; otherwise, the upgrade should be non-breaking for typical configurations

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
  • Testing2.0 h
  • Review / QA1.0 h
9.0 hours of engineering $1,600
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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-2024-47252 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