cve.bz

CAPEC-81

Web Server Logs Tampering

High severityMedium likelihoodDetailed pattern

Web Logs Tampering attacks involve an attacker injecting, deleting or otherwise tampering with the contents of web logs typically for the purposes of masking other malicious behavior. Additionally, writing malicious data to log files may target jobs, filters, reports, and other agents that process the logs in an asynchronous attack pattern. This pattern of attack is similar to "Log Injection-Tampering-Forging" except that in this case, the attack is targeting the logs of the web server and not the application.

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Show the promptExplain the attack pattern CAPEC-81: Web Server Logs Tampering: how it unfolds, what it needs and how to prevent and detect it in my systems. Use https://capec.mitre.org/data/definitions/81.html and https://cve.bz/cve/capec/81?via=ask-ai-copy, which lists recent CVEs with the weaknesses it exploits. Cite the sources.

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How the attack unfolds

  1. Explore

    The attacker looks for a way in.

    1. [Determine Application Web Server Log File Format] The attacker observes the system and looks for indicators of which logging utility is being used by the web server.

      1 technique
      • Determine logging utility being used by application web server (e.g. log4j), only possible if the application is known by the attacker or if the application returns error messages with logging utility information.

  2. Experiment

    They probe what they found.

    1. [Determine Injectable Content] The attacker launches various logged actions with malicious data to determine what sort of log injection is possible.

      1 technique
      • Attacker triggers logged actions with maliciously crafted data as inputs, parameters, arguments, etc.

  3. Exploit

    They carry out the attack.

    1. [Manipulate Log Files] The attacker alters the log contents either directly through manipulation or forging or indirectly through injection of specially crafted request that the web server will receive and write into the logs. This type of attack typically follows another attack and is used to try to cover the traces of the previous attack.

      3 techniques
      • Indirectly through injection, use carriage return and/or line feed characters to start a new line in the log file, and then, add a fake entry. For example: The HTTP request for "/index.html%0A%0DIP_ADDRESS- - DATE_FORMAT] "GET /forged-path HTTP/1.1" 200 - "-" USER_AGENT" may add the log line into Apache "access_log" (for example). Different applications may require different encodings of the carriage return and line feed characters.
      • Directly through log file or database manipulation, use carriage return and/or line feed characters to start a new line in the log file, and then, add a fake entry. For example: The HTTP request for "/index.html%0A%0DIP_ADDRESS- - DATE_FORMAT] "GET /forged-path HTTP/1.1" 200 - "-" USER_AGENT" may add the log line into Apache "access_log" (for example). Different applications may require different encodings of the carriage return and line feed characters.
      • Directly through log file or database manipulation, modify existing log entries.

Prerequisites

  • Target server software must be a HTTP server that performs web logging.

Skills required

  • Low skill

    To input faked entries into Web logs

Resources required

  • Ability to send specially formatted HTTP request to web server

Consequences

What a successful attack can lead to
ImpactAffectsNote
Modify DataIntegrity

Mitigations

  • Design: Use input validation before writing to web log

  • Design: Validate all log data before it is output

Weaknesses it exploits

  • CWE-20 Improper Input Validation
  • CWE-75 Failure to Sanitize Special Elements into a Different Plane
  • CWE-93 Improper Neutralization of CRLF Sequences
  • CWE-96 Improper Neutralization of Directives in Statically Saved Code
  • CWE-116 Improper Encoding or Escaping of Output
  • CWE-117 Improper Output Neutralization for Logs
  • CWE-150 Improper Neutralization of Escape, Meta, or Control Sequences
  • CWE-221 Information Loss or Omission
  • CWE-276 Incorrect Default Permissions
  • CWE-279 Incorrect Execution-Assigned Permissions

Recent CVEs with these weaknesses

  1. 9.6CVE-2026-108186

    Improper Input Validation in Zoom Workplace for Windows may allow an unauthenticated user to conduct an escalation of privilege via network access.

  2. 4.9CVE-2026-105427

    Improper input validation in Ivanti EPMM before version 12.10.0.1, 12.9.0.3, and 12.8.0.5 allows a remote authenticated attacker with admin privileges to permanently disable all Apache HTTPS services resulting in denial of service.

  3. 6.7CVE-2026-105426

    Improper input validation in Ivanti EPMM before version 12.10.0.1, 12.9.0.3, and 12.8.0.5 allows a remote authenticated attacker with admin privileges to set arbitrary Linux kernel parameters as root.

  4. 4.3CVE-2026-123178

    An insufficient input validation vulnerability in the listed NETGEAR Orbi Models router allows an authenticated administrator connected to the local network to execute unauthorized commands and modify the router’s software and functionalit…

  5. 6.3CVE-2026-125871

    The sourcecache expansion module in MISP Modules (misp-modules) contains a Server-Side Request Forgery (SSRF) vulnerability. When a user with permission to create or modify attributes of type 'link' or 'url' submits an attribute value, the…

  6. 7.8CVE-2026-121267

    Incorrect default permissions vulnerability in TÜBİTAK BİLGEM Software Technologies Research Institute eta-remote allows Accessing Functionality Not Properly Constrained by ACLs. This issue affects eta-remote: from 0.0.2 before 0.0.3.

  7. 4.8CVE-2026-120326

    DownloadEvent.setFileName(String) in Vaadin Flow writes the download file name into the Content-Disposition header without escaping it. When the name is pure US-ASCII the header is built as attachment; filename="<name>" with the name inser…

  8. 5.5CVE-2026-125703

    A flaw was found in the GStreamer gst-plugins-bad MXF plugin. Insufficient bounds checks when parsing crafted VANC data can cause an out-of-bounds read in the demuxer, while an incorrect buffer size calculation when muxing multiple ancilla…

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Part of

Examples

Most web servers have a public interface, even if the majority of the site is password protected, there is us…

Most web servers have a public interface, even if the majority of the site is password protected, there is usually at least a login site and brochureware that is publicly available. HTTP requests to the site are also generally logged to a Web log. From an attacker point of view, standard HTTP requests containing a malicious payload can be sent to the public website (with no other access required), when those requests appear in the log (such as http://victimsite/index.html?< malicious script> if they are followed by an administrator this may be sufficient to probe the administrator's host or local network.

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