CWE-62: UNIX Hard Link

Extended Description

Failure for a system to check for hard links can result in vulnerability to different types of attacks. For example, an attacker can escalate their privileges if a file used by a privileged program is replaced with a hard link to a sensitive file (e.g. /etc/passwd). When the process opens the file, the attacker can assume the privileges of that process.

Source-backed guidance

Additional facts reviewed against primary or authoritative security sources.

Verify controls for CWE-62 with SSDF evidence

Use NIST SSDF verification and vulnerability-response practices to detect CWE-62, UNIX Hard Link, throughout the product lifecycle. Derive review questions, static or dynamic checks, and negative tests from the CWE's causal behavior; define the components and lifecycle stages each check covers; and retain findings with enough evidence to distinguish the root cause from symptoms and impacts. Track escapes and false negatives, then improve the verification plan after every confirmed occurrence.

NIST SP 800-218 Secure Software Development Framework — National Institute of Standards and Technology

Apply Separation of Privilege controls for UNIX Hard Link

MITRE associates mitigation with Architecture and Design; the listed strategies include Separation of Privilege; recorded impacts include Read Files or Directories, and Modify Files or Directories. Use these source-defined anchors to turn CWE-62 into implementation, review, and verification checks for the affected component.

CWE-62: UNIX Hard Link — MITRE CWE

Triage CWE-62 against known exploitation evidence

Use CISA's Known Exploited Vulnerabilities catalog to test whether a vulnerability mapped to CWE-62, UNIX Hard Link, has evidence of exploitation in the wild. Confirm the CVE-to-CWE root-cause mapping independently before attaching the example, then capture the affected product, required action, and remediation deadline. A missing KEV match is not evidence that the weakness is unexploited, and a KEV entry must not be generalized to every occurrence of this CWE.

Known Exploited Vulnerabilities Catalog — Cybersecurity and Infrastructure Security Agency

Apply precise root-cause mapping to CWE-62

Apply MITRE's full root-cause mapping guidance when using CWE-62, UNIX Hard Link. Separate weakness language from attacker prerequisites and technical impact, check the entry's abstraction and vulnerability-mapping notes, and prefer the most specific Base or Variant supported by the evidence. Record the rejected alternatives and require an independent review before the mapping is used for remediation trends or program metrics.

CVE to CWE Root Cause Mapping Guidance — MITRE CWE

Validate CWE-62 with root-cause mapping checks

Apply MITRE's root-cause mapping quick tips to CWE-62, UNIX Hard Link. Confirm the finding describes the causal weakness rather than an impact or attack pattern, compare the abstraction and mapping notes with plausible alternatives, and have a second reviewer challenge the selection. Preserve the evidence and reasoning so recurring defects can be measured against one consistent identifier.

CVE to CWE Root Cause Mapping Quick Tips — MITRE CWE

Frequently Asked Questions

What is CWE-62: UNIX Hard Link?+

CWE-62: UNIX Hard Link is a Common Weakness Enumeration (CWE) entry maintained by MITRE. The product, when opening a file or directory, does not sufficiently account for when the name is associated with a hard link to a target that is outside of the intended control sphere. This could allow an attacker to cause the product to operate on unauthorized files. Failure for a system to check for hard links can result in vulnerability to different types of attacks. For example, an attacker can escalate their privileges if a file used by a privileged program is replaced with a hard link to a sensitive file (e.g. /etc/passwd). When the process opens the file, the attacker can assume the privileges of that process.

What are the security consequences of UNIX Hard Link?+

If exploited, CWE-62 (UNIX Hard Link) it can compromise Confidentiality and Integrity, leading to outcomes such as Read Files or Directories and Modify Files or Directories.

Which programming languages are affected by UNIX Hard Link?+

CWE-62 commonly affects Not Language-Specific. Note that weaknesses are often language-agnostic patterns, so secure coding practices apply broadly.

What are real-world examples of UNIX Hard Link?+

MITRE documents real CVEs mapped to CWE-62, including CVE-2001-1494, CVE-2002-0793, CVE-2003-0578, CVE-1999-0783 and CVE-2004-1603. You can look up the full details of each CVE, including CVSS scores and remediation guidance, on our CVE Lookup tool.

What is the difference between a CWE and a CVE?+

A CWE (Common Weakness Enumeration) like CWE-62 describes a category of software weakness — the underlying flaw type. A CVE (Common Vulnerabilities and Exposures) identifies a specific, real-world vulnerability in a particular product. In short, a CWE is the kind of mistake, and a CVE is an instance of that mistake being found in software.

CWE-62: UNIX Hard Link

Extended Description

Technical Details

Applicable To

Security Consequences

Scope

Impact

Mitigation Strategies

Detection Methods

Code Examples & CVEs

Observed CVE Examples (10)

CWE Relationships

Parent Weaknesses