CVE-2022-4797

Executive Summary

CVE-2022-4797 is a critical severity vulnerability affecting the usememos/memos application, an open-source self-hosted note-taking and knowledge management platform. The flaw, classified as an Improper Restriction of Excessive Authentication Attempts, affects all versions prior to 0.9.1 and allows an attacker to perform unlimited brute-force authentication attempts against the web application. With a CVSS score of 9.8, this vulnerability enables remote attackers to compromise user accounts, including administrative accounts, exposing all notes and memos stored in the application. The product is self-hosted, meaning any organization deploying memos without proper network controls is at risk of account takeover.

Technical Analysis

The CVE-2022-4797 vulnerability falls under the CWE class of "Improper Restriction of Excessive Authentication Attempts" (CWE-307). This vulnerability class arises when an application fails to implement adequate rate limiting, account lockout mechanisms, or exponential backoff on failed login attempts, thereby permitting an attacker to make unlimited guesses at user credentials.

The affected component is the authentication mechanism of usememos/memos. The NVD description explicitly indicates that the vulnerability exists in the repository "prior to 0.9.1," meaning the fix was introduced in version 0.9.1. The description provides no additional technical details about the specific function names, file paths, or authentication flow endpoints. Per the accuracy constraints of this report, we will describe the vulnerability at the attack-mechanism level without inventing implementation details.

The attack surface is the publicly accessible login interface of the self-hosted memos application. Since memos is deployed on web servers and accessed via HTTP/HTTPS, the authentication endpoint is reachable by any network entity. The failure to restrict the rate of authentication attempts means that:

• There is no lockout policy after a predefined number of failed attempts.
• There is no IP-based rate limiting to slow down repeated requests.
• There is no CAPTCHA or other human-verification mechanism to obviate automated attempts.

This makes the application trivially susceptible to credential stuffing and dictionary attacks. Because the application stores user data (notes and memos) and may host multiple user accounts, the impact is not limited to a single account—an attacker who successfully obtains valid credentials for any user can access that user's stored memories, and if administrative credentials are obtained, the attacker gains full control over the memos instance.

The CVSS vector (9.8) suggests a network-based attack vector with low attack complexity and low privileges required for exploitation. The high base score is typical of brute-force-capable authentication flaws since they require no user interaction and can lead to complete compromise of the application's data confidentiality.

Exploitation Scenarios

No public PoC or exploit code is currently available for CVE-2022-4797. The attack chain below is inferred from the vulnerability class (Improper Restriction of Excessive Authentication Attempts) and the data provided. Insufficient technical detail is available to specify exact endpoints or payload formats; the analysis is at the class level.

Step 1 - Reconnaissance/Target Identification: An attacker identifies instances of usememos/memos deployed on the internet. Since memos is advertised as a self-hostable application, internet-wide scans (e.g., using search engines for default login pages or application banners) can yield target IPs. The attacker would look for the memos login page, which is the primary interface for user authentication.

Step 2 - Triggering the Authentication Flaw: The attacker initiates an HTTP request to the authentication endpoint with a username and a candidate password. Because the application does not enforce an upper bound on failed authentication attempts, the attacker can repeat this request indefinitely without hitting a lockout or encountering a rate limit (e.g., 429 HTTP status). This allows the attacker to cycle through a large wordlist of common passwords.

Step 3 - Payload/Execution Method: At the vulnerability-class level, the attacker uses automated tooling (e.g., web application brute-force tools) to submit POST requests to the login endpoint, varying the password parameter for each account. The attack does not require crafted payloads or injection—plaintext credential guessing suffices. The success criterion is a non-401/403 response indicating a valid authentication session (e.g., a session cookie or a redirect to the application dashboard).

Step 4 - Post-Exploitation Impact: Once valid credentials are obtained, the attacker logs in as the victim user and reads, modifies, or deletes all memos and notes stored under that account. If the brute-forced account is an administrator, the attacker gains full administrative control over the memos instance, potentially enabling user enumeration, mass data extraction, and configuration changes. The attacker could also leverage the compromised instance as a foothold for lateral movement within the internal network if the self-hosted server is on an internal subnet.

Impact Assessment

The business impact of CVE-2022-4797 is severe for what is fundamentally an authentication bypass issue. The CVSS base score of 9.8 places this in the critical severity band. Although the official NVD vector string is not provided, a 9.8 score is consistent with:

• Attack Vector (AV): Network — remotely exploitable without any network adjacency.
• Attack Complexity (AC): Low — no special conditions beyond reaching the login page.
• Privileges Required (PR): None — the attacker needs no prior account access.
• User Interaction (UI): None — no victim interaction is needed.
• Confidentiality Impact (C): High — full unauthorized read of all notes/memos.
• Integrity Impact (I): High — attacker can modify or delete stored data.
• Availability Impact (A): High — attacker can delete all data or lock out legitimate users.

The blast radius is limited to a single memos instance, which is a self-hosted application—affecting any organization that deploys it. Small-to-medium teams are the typical users of memos, making data confidentiality of internal knowledge the primary asset at risk. There is no evidence of exploitation in the wild (EPSS 0.00713, 50.2% percentile), and the CISA KEV list does not include this CVE. However, the absence of a patch (confidence 0/4) elevates the risk for any exposed instance, as attackers may discover this flaw and develop exploits over time.

Detection Guidance

The following detection rules are heuristic and based on the vulnerability class (excessive authentication attempts). They are designed to detect abnormal volumes of login failures, which are the primary observable indicators of brute-force activity.

Sigma Rule

title: Excessive Authentication Attempts on usememos/memos
id: a3f7e6d2-8b4c-4f1a-9e5c-1d2b3a4c5d6e
status: experimental
description: Detects a high volume of failed login attempts against a memos instance, indicating potential brute-force activity (CVE-2022-4797).
logsource:
    category: web
    product: nginx
    service: http
detection:
    selection:
        http.response.body|contains: 'invalid credentials'
        http.response.status_code: 401
    timeframe: 5m
    condition: selection | count() by c-ip > 30
level: high
falsepositives:
    - Legitimate users mistyping passwords
    - Scripted admin health checks
tags:
    - attack.credential_access
    - cve.2022-4797
    - brute.force

YARA Rule

rule Detect_Memos_BruteForce_Logs
{
    meta:
        author = "Valters IT Security"
        description = "Detect log patterns indicating brute-force attempts against usememos/memos instances"
        reference = "CVE-2022-4797"
        date = "2025-01-01"

    strings:
        $login_failure = /Failed (to )?(login|sign in)/ nocase
        $auth_error = /invalid (username|password|credentials)/ nocase
        $http_401 = " 401 "
        $source_ip = /\b(?:\d{1,3}\.){3}\d{1,3}\b/

    condition:
        (any of ($login_failure, $auth_error) and $http_401) and #source_ip > 5
}

Suricata IDS Rule

alert http any any -> any any (msg:"Memos Excessive Authentication Attempts - Potential Brute-Force (CVE-2022-4797)"; flow:to_server; http.method; content:"POST"; http.uri; content:"/auth/"; http.response_body; content:"invalid"; http.response_body; content:"credentials"; threshold: type both, track by_src, count 30, seconds 300; classtype:attempted-admin; reference:cve,2022-4797; sid:2022479701; rev:1;)

Note: The URI path /auth/ is used as an example; actual paths may vary — adjust based on application logs.

Elastic Detection

sequence by source.ip with maxspan=5m
  [authentication where event.outcome == "failure" and process.name : "*memos*"]
  [authentication where event.outcome == "failure" and process.name : "*memos*"]
  [authentication where event.outcome == "failure" and process.name : "*memos*"]
  [authentication where event.outcome == "failure" and process.name : "*memos*"]
  [authentication where event.outcome == "failure" and process.name : "*memos*"]

Splunk SPL Query

index=web sourcetype=access_combined
| stats count(eval(status=401)) as failed_attempts by src_ip
| where failed_attempts > 30
| eval timeframe_duration="5m"
| table src_ip, failed_attempts, timeframe_duration
| append [search index=proxy sourcetype=cisco_wsa
    | stats count by clientip
    | where count > 50
    | eval src_ip=clientip, failed_attempts=count, timeframe_duration="1h"
    | table src_ip, failed_attempts, timeframe_duration]

Wazuh OSSEC Rule

<group name="web, authentication,">
  <rule id="100300" level="10">
    <decoded_as>web</decoded_as>
    <match>invalid credentials|login failed|authentication failure</match>
    <description>Memos: Failed authentication detected - possible brute-force (CVE-2022-4797)</description>
    <group>cve-2022-4797,</group>
    <frequency>30</frequency>
    <timeframe>300</timeframe>
    <same_source_ip />
    <alert_level>10</alert_level>
  </rule>
</group>

Mitigation & Patch Guidance

Patch Confidence: 0/4 — UNPATCHED. No patch evidence is available from NVD, OSV, or vendor advisories. The NVD description states the fix was introduced in memos version 0.9.1, but our tracked sources have not confirmed an official vendor patch notice. The absence of patch validation suggests that many instances may still run unpatched.

1. Immediate Mitigations:

• Network-Level Access Control: Restrict access to the memos web interface to only trusted IP ranges or VPN users. Disable internet-facing exposure if remote access is not strictly necessary.
• Reverse Proxy Rate Limiting: Deploy nginx or another reverse proxy in front of memos and configure limit_req_zone to throttle login requests per client IP (e.g., 10 requests per minute to the login endpoint).
• Fail2Ban: Configure Fail2Ban rules to block IPs that exceed a threshold of failed HTTP authentications (e.g., 5 failures in 10 minutes).
• Disable Default Accounts: Immediately disable or change any default admin credentials to strong, unique passwords.
• Enable Multi-Factor Authentication: If memos supports MFA (or if a future version does), enable it for all accounts to add a second layer of defense.

2. Patch/Upgrade Steps:

• Upgrade to memos version 0.9.1 or later. This is the version NVD indicates includes the fix. Verify the version running via the application's settings/build info page. If the version is older than 0.9.1, upgrade immediately.
• Monitor Official Repositories: Regularly check the usememos/memos GitHub releases page for security advisories and follow upstream changelogs for any subsequent security fixes.

3. Long-Term Hardening:

• Centralized Authentication: Replace local credentials with an external identity provider (e.g., LDAP, OAuth2, SAML) where the provider enforces account lockout and rate limiting.
• Security Audits: Perform periodic penetration tests of self-hosted applications to identify missing security controls outside the known CVE disclosure.
• Belt-and-Suspenders Monitoring: Deploy the detection rules from the Detection Guidance section in your SIEM to catch brute-force activity even after patching.
• Backup and Disaster Recovery: Maintain regular backups of the memos database to ensure recovery from data destruction caused by an attacker who gains admin access.

References

• NVD Entry: https://nvd.nist.gov/vuln/detail/CVE-2022-4797
• GitHub Advisory / CNA Record: https://github.com/advisories?query=CVE-2022-4797 (official huntr.dev CNA advisory)
• usememos/memos GitHub Repository: https://github.com/usememos/memos (for version history and release notes)
• CWE-307: https://cwe.mitre.org/data/definitions/307.html (Improper Restriction of Excessive Authentication Attempts)

No known threat actor campaigns or exploits-in-the-wild targeting CVE-2022-4797 have been documented at the time of this report. The CVE is not included in the CISA KEV catalog. The absence of public exploit code should not be misread as low risk—the vulnerability class is well understood and widely automated by brute-force tooling.