Argo CD is a declarative, GitOps continuous delivery tool for Kubernetes. Prior to versions 2.8.13, 2.9.9, and 2.10.4, an attacker can effectively bypass the rate limit and brute force protections by exploiting the application's weak cache-based mechanism. This loophole in security can be combined with other vulnerabilities to attack the default admin account. This flaw undermines a patch for CVE-2020-8827 intended to protect against brute-force attacks. The application's brute force protection relies on a cache mechanism that tracks login attempts for each user. This cache is limited to a `defaultMaxCacheSize` of 1000 entries. An attacker can overflow this cache by bombarding it with login attempts for different users, thereby pushing out the admin account's failed attempts and effectively resetting the rate limit for that account. This is a severe vulnerability that enables attackers to perform brute force attacks at an accelerated rate, especially targeting the default admin account. Users should upgrade to version 2.8.13, 2.9.9, or 2.10.4 to receive a patch.

Affected: Go: github.com/argoproj/argo-cd/v2

### Summary An attacker can effectively bypass the rate limit and brute force protections by exploiting the application's weak cache-based mechanism. This loophole in security can be combined with other vulnerabilities to attack the default admin account. This flaw undermines a previously [patched CVE](https://argo-cd.readthedocs.io/en/stable/security_considerations/#cve-2020-8827-insufficient-anti-automationanti-brute-force) intended to protect against brute-force attacks.

### Details The application's brute force protection relies on a cache mechanism that tracks login attempts for each user. This cache is limited to a `defaultMaxCacheSize` of 1000 entries. An attacker can overflow this cache by bombarding it with login attempts for different users, thereby pushing out the admin account's failed attempts and effectively resetting the rate limit for that account.

The brute force protection mechanism's code: ```go if failed && len(failures) >= getMaximumCacheSize() { log.Warnf("Session cache size exceeds %d entries, removing random entry",

getMaximumCacheSize()) idx := rand.Intn(len(failures) - 1) var rmUser string i := 0 for key := range failures {

if i == idx { rmUser = key

delete(failures, key)

break

}

i++ }

log.Infof("Deleted entry for user %s from cache", rmUser) } ```

### PoC 1. Set up the application environment and identify the login page. 2. Execute 4 failed login atte…

CD: Users with `create` but not `override` privileges can perform local sync argo-cd: Bypassing Brute Force Protection via Application Crash and In-Memory Data Loss argo-cd: Denial of Service Due to Unsafe Array Modification in Multi-threaded Environment argo-cd: Bypassing Rate Limit and Brute Force Protection Using Cache Overflow argo-cd: uncontrolled memory allocation vulnerability

Ein entfernter, anonymer Angreifer kann mehrere Schwachstellen in Red Hat OpenShift ausnutzen, um einen Denial of Service Angriff durchzuführen oder um Sicherheitsmaßnahmen zu umgehen.