cve.bz

CAPEC-78

Using Escaped Slashes in Alternate Encoding

High severityHigh likelihoodDetailed pattern

This attack targets the use of the backslash in alternate encoding. An adversary can provide a backslash as a leading character and causes a parser to believe that the next character is special. This is called an escape. By using that trick, the adversary tries to exploit alternate ways to encode the same character which leads to filter problems and opens avenues to attack.

On this page

Ask an AI about this attack pattern

ChatGPTClaudeGoogle AI Mode

Show the promptExplain the attack pattern CAPEC-78: Using Escaped Slashes in Alternate Encoding: how it unfolds, what it needs and how to prevent and detect it in my systems. Use https://capec.mitre.org/data/definitions/78.html and https://cve.bz/cve/capec/78?via=ask-ai-copy, which lists recent CVEs with the weaknesses it exploits. Cite the sources.

Opens a third-party assistant; its answer is its own, not cve.bz's. The prompt holds only this attack pattern's id and public links.

How the attack unfolds

  1. Explore

    The attacker looks for a way in.

    1. [Survey the application for user-controllable inputs] Using a browser, an automated tool or by inspecting the application, an adversary records all entry points to the application.

      4 techniques
      • Use a spidering tool to follow and record all links and analyze the web pages to find entry points. Make special note of any links that include parameters in the URL.
      • Use a proxy tool to record all user input entry points visited during a manual traversal of the web application.
      • Use a browser to manually explore the website and analyze how it is constructed. Many browsers' plugins are available to facilitate the analysis or automate the discovery.
      • Manually inspect the application to find entry points.

  2. Experiment

    They probe what they found.

    1. [Probe entry points to locate vulnerabilities] The adversary uses the entry points gathered in the "Explore" phase as a target list and attempts to escape multiple different special characters using a backslash.

      2 techniques
      • Escape a special character with a backslash to bypass input validation.
      • Try different encodings of both the backslash and the special character to see if this bypasses input validation

  3. Exploit

    They carry out the attack.

    1. [Manipulate input] Once the adversary determines how to bypass filters that filter out special characters using an escaped slash, they will manipulate the user input in a way that is not intended by the application.

Prerequisites

  • The application accepts the backlash character as escape character.

  • The application server does incomplete input data decoding, filtering and validation.

Skills required

  • Low skill

    The adversary can naively try backslash character and discover that the target host uses it as escape character.

  • Medium skill

    The adversary may need deep understanding of the host target in order to exploit the vulnerability. The adversary may also use automated tools to probe for this vulnerability.

Signs of an attack

  • An adversary can use a fuzzer in order to probe for this vulnerability. The fuzzer should generate suspicious network activity noticeable by an intrusion detection system.

Consequences

What a successful attack can lead to
ImpactAffectsNote
Read DataConfidentiality
Resource ConsumptionAvailabilityDenial of Service
Execute Unauthorized CommandsConfidentiality, Integrity, AvailabilityRun Arbitrary Code
Bypass Protection MechanismConfidentiality, Access Control, Authorization

Mitigations

  • Verify that the user-supplied data does not use backslash character to escape malicious characters.

  • Assume all input is malicious. Create an allowlist that defines all valid input to the software system based on the requirements specifications. Input that does not match against the allowlist should not be permitted to enter into the system.

  • Be aware of the threat of alternative method of data encoding.

  • Regular expressions can be used to filter out backslash. Make sure you decode before filtering and validating the untrusted input data.

  • In the case of path traversals, use the principle of least privilege when determining access rights to file systems. Do not allow users to access directories/files that they should not access.

  • Any security checks should occur after the data has been decoded and validated as correct data format. Do not repeat decoding process, if bad character are left after decoding process, treat the data as suspicious, and fail the validation process.

  • Avoid making decisions based on names of resources (e.g. files) if those resources can have alternate names.

Weaknesses it exploits

  • CWE-20 Improper Input Validation
  • CWE-22 Improper Limitation of a Pathname to a Restricted Directory
  • CWE-73 External Control of File Name or Path
  • CWE-74 Improper Neutralization of Special Elements in Output Used by a Downstream Component
  • CWE-172 Improper Encoding or Decoding of Data
  • CWE-173 Improper Handling of Alternate Encoding
  • CWE-180 Incorrect Behavior Order: Validate Before Canonicalize
  • CWE-181 Incorrect Behavior Order: Validate Before Filter
  • CWE-697 Incorrect Comparison
  • CWE-707 Improper Neutralization

Recent CVEs with these weaknesses

  1. 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.

  2. 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.

  3. 5.5CVE-2026-123181

    A path traversal vulnerability in Ivanti Sentry before versions 10.7.4 and 10.8.3 allows a remote authenticated attacker with administrative privileges to create arbitrary directories and files with root privileges.

  4. –CVE-2026-97881

    The embedded OpenEJB HTTP server does not restrict static resource paths to the configured resource directories. A remote unauthenticated attacker can read arbitrary files accessible to the server process. Users are recommended to block ne…

  5. 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.

  6. 8.2CVE-2026-125753

    ABP Framework 2.9.0 before 10.6.2 and 10.7.0 pre-releases before 10.7.0 contain a path traversal vulnerability in DefaultBlobFilePathCalculator that allows unauthenticated attackers to access files outside the blob container. Attackers can…

  7. –CVE-2026-86811

    The stateful session bean passivation mechanism derives the on-disk file name from a client-supplied identifier without validating it. A remote attacker with access to the remote EJB service can cause session state to be read from or writt…

  8. 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…

The newest records naming one of them. Each weakness's page lists them all.

Part of

Examples

For example, the byte pair \0 might result in a single zero byte (a NULL) being sent. Another example is \t, …

For example, the byte pair \0 might result in a single zero byte (a NULL) being sent. Another example is \t, which is sometimes converted into a tab character. There is often an equivalent encoding between the back slash and the escaped back slash. This means that \/ results in a single forward slash. A single forward slash also results in a single forward slash. The encoding looks like this:

/ yields /
\/ yields /
An attack leveraging escaped slashes in slternate encodings is very simple. If you believe the target may be …

An attack leveraging escaped slashes in slternate encodings is very simple. If you believe the target may be filtering the slash, attempt to supply \/ and see what happens. Example command strings to try out include

CWD ..\/..\/..\/..\/winnt

which converts in many cases to

CWD ../../../../winnt

To probe for this kind of problem, a small C program that uses string output routines can be very useful. File system calls make excellent testing fodder. The simple snippet

int main(int argc, char* argv[])
{
  puts("\/ \\ \? \. \| ");
  return 0;

}

produces the output

/ \ ? . |

Clearly, the back slash is ignored, and thus we have hit on a number of alternative encodings to experiment with. Given our previous example, we can extend the attack to include other possibilities:

CWD ..\?\?\?\?\/..\/..\/..\/winnt
CWD \.\.\/\.\.\/\.\.\/\.\.\/winnt
CWD ..\|\|\|\|\/..\/..\/..\/winnt

MITRE's words, unchanged: CAPEC-78 at MITRE. CAPEC is Copyright © 2007–2026, The MITRE Corporation, used under the CAPEC terms of use: “The MITRE Corporation (MITRE) hereby grants you a non-exclusive, royalty-free license to use Common Attack Pattern Enumeration and Classification (CAPEC™) for research, development, and commercial purposes. Any copy you make for such purposes is authorized provided that you reproduce MITRE’s copyright designation and this license in any such copy.” CAPEC and the CAPEC logo are trademarks of The MITRE Corporation. Credits. All attack patterns.