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CAPEC-45

Buffer Overflow via Symbolic Links

High severityHigh likelihoodDetailed pattern

This type of attack leverages the use of symbolic links to cause buffer overflows. An adversary can try to create or manipulate a symbolic link file such that its contents result in out of bounds data. When the target software processes the symbolic link file, it could potentially overflow internal buffers with insufficient bounds checking.

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How the attack unfolds

  1. Explore

    The attacker looks for a way in.

    1. [Identify target application] The adversary identifies a target application or program that might load in certain files to memory.

  2. Experiment

    They probe what they found.

    1. [Find injection vector] The adversary identifies an injection vector to deliver the excessive content to the targeted application's buffer.

      1 technique
      • The adversary creates or modifies a symbolic link pointing to those files which contain an excessive amount of data. If creating a symbolic link to one of those files causes different behavior in the application, then an injection vector has been identified.

    2. [Craft overflow file content] The adversary crafts the content to be injected. If the intent is to simply cause the software to crash, the content need only consist of an excessive quantity of random data. If the intent is to leverage the overflow for execution of arbitrary code, the adversary crafts the payload in such a way that the overwritten return address is replaced with one of the adversary's choosing.

      2 techniques
      • Create malicious shellcode that will execute when the program execution is returned to it.
      • Use a NOP-sled in the overflow content to more easily "slide" into the malicious code. This is done so that the exact return address need not be correct, only in the range of all of the NOPs

  3. Exploit

    They carry out the attack.

    1. [Overflow the buffer] Using the specially crafted file content, the adversary creates a symbolic link from the identified resource to the malicious file, causing a targeted buffer overflow attack.

Prerequisites

  • The adversary can create symbolic link on the target host.

  • The target host does not perform correct boundary checking while consuming data from a resources.

Skills required

  • Low skill

    An adversary can simply overflow a buffer by inserting a long string into an adversary-modifiable injection vector. The result can be a DoS.

  • High skill

    Exploiting a buffer overflow to inject malicious code into the stack of a software system or even the heap can require a higher skill level.

Signs of an attack

  • An adversary creating or modifying Symbolic links is a potential signal of attack in progress.

  • An adversary deleting temporary files can also be a sign that the adversary is trying to replace legitimate resources with malicious ones.

Consequences

What a successful attack can lead to
ImpactAffectsNote
Unreliable ExecutionAvailability
Execute Unauthorized CommandsConfidentiality, Integrity, AvailabilityRun Arbitrary Code
Read DataConfidentiality
Modify DataIntegrity

Mitigations

  • Pay attention to the fact that the resource you read from can be a replaced by a Symbolic link. You can do a Symlink check before reading the file and decide that this is not a legitimate way of accessing the resource.

  • Because Symlink can be modified by an adversary, make sure that the ones you read are located in protected directories.

  • Pay attention to the resource pointed to by your symlink links (See attack pattern named "Forced Symlink race"), they can be replaced by malicious resources.

  • Always check the size of the input data before copying to a buffer.

  • Use a language or compiler that performs automatic bounds checking.

  • Use an abstraction library to abstract away risky APIs. Not a complete solution.

  • Compiler-based canary mechanisms such as StackGuard, ProPolice and the Microsoft Visual Studio /GS flag. Unless this provides automatic bounds checking, it is not a complete solution.

  • Use OS-level preventative functionality. Not a complete solution.

Weaknesses it exploits

  • CWE-20 Improper Input Validation
  • CWE-74 Improper Neutralization of Special Elements in Output Used by a Downstream Component
  • CWE-118 Incorrect Access of Indexable Resource
  • CWE-119 Improper Restriction of Operations within the Bounds of a Memory Buffer
  • CWE-120 Buffer Copy without Checking Size of Input
  • CWE-285 Improper Authorization
  • CWE-302 Authentication Bypass by Assumed-Immutable Data
  • CWE-680 Integer Overflow to Buffer Overflow
  • CWE-697 Incorrect Comparison

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. 8.8CVE-2026-124948

    Incorrect boundary conditions, use-after-free in the Graphics component. This vulnerability was fixed in Firefox 160 and Firefox ESR 153.7.

  6. 8.8CVE-2026-124947

    Incorrect boundary conditions in the Graphics component. This vulnerability was fixed in Firefox 160.

  7. 8.8CVE-2026-124926

    Incorrect boundary conditions in the WebRTC component. This vulnerability was fixed in Firefox 160 and Firefox ESR 153.7.

  8. 8.8CVE-2026-124924

    Incorrect boundary conditions in the Graphics: WebRender component. This vulnerability was fixed in Firefox 160 and Firefox ESR 153.7.

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

Part of

Examples

The EFTP server has a buffer overflow that can be exploited if an adversary uploads a .lnk (link) file that c…

The EFTP server has a buffer overflow that can be exploited if an adversary uploads a .lnk (link) file that contains more than 1,744 bytes. This is a classic example of an indirect buffer overflow. First the adversary uploads some content (the link file) and then the adversary causes the client consuming the data to be exploited. In this example, the ls command is exploited to compromise the server software.

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