CWE-645: Overly Restrictive Account Lockout Mechanism
The product contains an account lockout protection mechanism, but the mechanism is too restrictive and can be triggered too easily, which allows attackers to deny service to legitimate users by causing their accounts to be locked out.
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Overview
Account lockout is a security feature often present in applications as a countermeasure to the brute force attack on the password based authentication mechanism of the system. After a certain number of failed login attempts, the users' account may be disabled for a certain period of time or until it is unlocked by an administrator. Other security events may also possibly trigger account lockout. However, an attacker may use this very security feature to deny service to legitimate system users. It is therefore important to ensure that the account lockout security mechanism is not overly restrictive.
Real-world CVEs
7 recorded CVEs are caused by CWE-645 (Overly Restrictive Account Lockout Mechanism), including 1 in CISA's KEV (Known Exploited Vulnerabilities) catalog. KEVs are shown first. 2 new CWE-645 CVEs have been recorded so far in 2026 (2 in 2025).
- CVE-2023-4346CISA KEVHigh · CVSS 7.5 · EPSS 68th2023-08-29
- CVE-2026-25907High · CVSS 7.5 · EPSS 18th2026-03-04
- CVE-2026-53982
Cap-go Console < 12.28.2 Account Deletion DoS via Device Identifier Association
High · CVSS 7.1 · EPSS 25th2026-06-12 - CVE-2024-37028Medium · CVSS 6.3 · EPSS 37th2024-08-14
- CVE-2025-31947
Repeated LDAP login failures can lock an LDAP account
Medium · CVSS 5.8 · EPSS 26th2025-05-15 - CVE-2025-5241
Denial-of-Service Vulnerability in MELSEC iQ-F Series
Medium · CVSS 5.3 · EPSS 32th2025-07-11 - CVE-2024-1722
Keycloak-core: dos via account lockout
Medium · CVSS 5.3 · EPSS 53th2024-02-27
Common consequences
What can happen when CWE-645 is exploited.
DoS: Resource Consumption (Other)
Affects: Availability
Users could be locked out of accounts.
How it happens
When it is introduced
Typically introduced during these phases of the software lifecycle.
How to prevent it
Practical mitigations for CWE-645, grouped by where in the lifecycle they apply.
Implement more intelligent password throttling mechanisms such as those which take IP address into account, in addition to the login name.
Implement a lockout timeout that grows as the number of incorrect login attempts goes up, eventually resulting in a complete lockout.
Consider alternatives to account lockout that would still be effective against password brute force attacks, such as presenting the user machine with a puzzle to solve (makes it do some computation).
Code examples
Illustrative examples from MITRE showing how the weakness appears in code.
A famous example of this type of weakness being exploited is the eBay attack. eBay always displays the user id of the highest bidder. In the final minutes of the auction, one of the bidders could try to log in as the highest bidder three times. After three incorrect log in attempts, eBay password throttling would kick in and lock out the highest bidder's account for some time. An attacker could then make their own bid and their victim would not have a chance to place the counter bid because they would be locked out. Thus an attacker could win the auction.
Attack patterns
CAPEC attack patterns that exploit this weakness.
Frequently asked questions
Common questions about CWE-645.
- What is CWE-645?
- The product contains an account lockout protection mechanism, but the mechanism is too restrictive and can be triggered too easily, which allows attackers to deny service to legitimate users by causing their accounts to be locked out.
- What CVEs are caused by CWE-645?
- 7 recorded CVEs are attributed to CWE-645, including CVE-2023-4346, CVE-2026-25907, CVE-2026-53982. 1 are listed in CISA's Known Exploited Vulnerabilities (KEV) catalog.
- How do you prevent CWE-645?
- Implement more intelligent password throttling mechanisms such as those which take IP address into account, in addition to the login name.
- What are the consequences of CWE-645?
- Exploiting CWE-645 can lead to: DoS: Resource Consumption (Other).
- Is CWE-645 actively exploited?
- Yes. 1 CWE-645 vulnerabilities are in CISA's KEV catalog of actively exploited flaws, out of 7 recorded CVEs.
References
- MITRE CWE definition (CWE-645) (opens in a new tab)
- CWE-645 vulnerabilities on NVD (opens in a new tab)
- Learn: What is a CWE?
Weakness data is sourced from the MITRE CWE catalog (v4.20). CVE associations are aggregated and kept current by RadicalNotion.AI.
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