CWE-640: Weak Password Recovery Mechanism for Forgotten Password

BaseIncompleteExploit Likelihood: High

The product contains a mechanism for users to recover or change their passwords without knowing the original password, but the mechanism is weak.

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Extended Description

It is common for an application to have a mechanism that provides a means for a user to gain access to their account in the event they forget their password. Very often the password recovery mechanism is weak, which has the effect of making it more likely that it would be possible for a person other than the legitimate system user to gain access to that user's account. Weak password recovery schemes completely undermine a strong password authentication scheme. This weakness may be that the security question is too easy to guess or find an answer to (e.g. because the question is too common, or the answers can be found using social media). Or there might be an implementation weakness in the password recovery mechanism code that may for instance trick the system into e-mailing the new password to an e-mail account other than that of the user. There might be no throttling done on the rate of password resets so that a legitimate user can be denied service by an attacker if an attacker tries to recover their password in a rapid succession. The system may send the original password to the user rather than generating a new temporary password. In summary, password recovery functionality, if not carefully designed and implemented can often become the system's weakest link that can be misused in a way that would allow an attacker to gain unauthorized access to the system.

Technical Details

Structure
Simple

Applicable To

Languages
Not Language-Specific
Platforms

Source-backed guidance

Additional facts reviewed against primary or authoritative security sources.

Verify controls for CWE-640 with SSDF evidence

Use NIST SSDF verification and vulnerability-response practices to detect CWE-640, Weak Password Recovery Mechanism for Forgotten Password, 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

Address Weak Password Recovery Mechanism for Forgotten Password during Architecture and Design

MITRE associates mitigation with Architecture and Design; recorded impacts include Gain Privileges or Assume Identity, DoS: Resource Consumption (Other), and Other; the entry maps to CAPEC-50. Use these source-defined anchors to turn CWE-640 into implementation, review, and verification checks for the affected component.

CWE-640: Weak Password Recovery Mechanism for Forgotten Password — MITRE CWE

Triage CWE-640 against known exploitation evidence

Use CISA's Known Exploited Vulnerabilities catalog to test whether a vulnerability mapped to CWE-640, Weak Password Recovery Mechanism for Forgotten Password, 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-640

Apply MITRE's full root-cause mapping guidance when using CWE-640, Weak Password Recovery Mechanism for Forgotten Password. 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-640 with root-cause mapping checks

Apply MITRE's root-cause mapping quick tips to CWE-640, Weak Password Recovery Mechanism for Forgotten Password. 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-640: Weak Password Recovery Mechanism for Forgotten Password?+

CWE-640: Weak Password Recovery Mechanism for Forgotten Password is a Common Weakness Enumeration (CWE) entry maintained by MITRE. The product contains a mechanism for users to recover or change their passwords without knowing the original password, but the mechanism is weak. It is common for an application to have a mechanism that provides a means for a user to gain access to their account in the event they forget their password. Very often the password recovery mechanism is weak, which has the effect of making it more likely that it would be possible for a person other than the legitimate system user to gain access to that user's account. Weak password recovery schemes completely undermine a strong password authentication scheme. This weakness may be that the security question is too easy to guess or find an answer to (e.g. because the question is too common, or the answers can be found using social media). Or there might be an implementation weakness in the password recovery mechanism code that may for instance trick the system into e-mailing the new password to an e-mail account other than that of the user. There might be no throttling done on the rate of password resets so that a legitimate user can be denied service by an attacker if an attacker tries to recover their password in a rapid succession. The system may send the original password to the user rather than generating a new temporary password. In summary, password recovery functionality, if not carefully designed and implemented can often become the system's weakest link that can be misused in a way that would allow an attacker to gain unauthorized access to the system.

What are the security consequences of Weak Password Recovery Mechanism for Forgotten Password?+

If exploited, CWE-640 (Weak Password Recovery Mechanism for Forgotten Password) it can compromise Access Control, Availability, Integrity and Other, leading to outcomes such as Gain Privileges or Assume Identity, DoS: Resource Consumption (Other) and Other.

How do you prevent or mitigate Weak Password Recovery Mechanism for Forgotten Password?+

Recommended mitigations for CWE-640 include: Make sure that all input supplied by the user to the password recovery mechanism is thoroughly filtered and validated. Do not use standard weak security questions and use several security questions. Make sure that there is throttling on the number of incorrect answers to a security question. Disable the password recovery functionality after a certain (small) number of incorrect guesses.

Which programming languages are affected by Weak Password Recovery Mechanism for Forgotten Password?+

CWE-640 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 Weak Password Recovery Mechanism for Forgotten Password?+

MITRE documents real CVEs mapped to CWE-640, including CVE-2025-1570, CVE-2024-9302, CVE-2024-5277 and CVE-2024-38287. 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-640 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.

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