Base weakness
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.
Last updated
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.
8 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. 3 new CWE-645 CVEs have been recorded so far in 2026 (2 in 2025).
Cap-go Console < 12.28.2 Account Deletion DoS via Device Identifier Association
Repeated LDAP login failures can lock an LDAP account
Denial-of-Service Vulnerability in MELSEC iQ-F Series
Keycloak-core: dos via account lockout
What can happen when CWE-645 is exploited.
DoS: Resource Consumption (Other)
Affects: Availability
Users could be locked out of accounts.
Typically introduced during these phases of the software lifecycle.
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).
MITRE examples of the weakness 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.
CAPEC attack patterns that exploit this weakness.
Common questions about CWE-645.
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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