CVE-2026-1848: 
MongoDB vulnerability analysis and mitigation

CVE-2026-1848 is a resource exhaustion vulnerability in MongoDB Server affecting the proxy port connection handling. Connections received via the proxy port may not be counted toward the server's total accepted connection limit, allowing the total number of connections to exceed available resources and resulting in server crashes. The vulnerability affects MongoDB 7.0.0–7.0.28, 8.0.0–8.0.17, and 8.2.0–8.2.3. It was published on February 10, 2026, with a patch reference added on February 25, 2026. It carries a CVSS v3.1 base score of 7.5 (High) and a CVSS v4.0 base score of 8.2 (High) (Red Hat CVE, MongoDB Jira).

The root cause is classified as CWE-770 (Allocation of Resources Without Limits or Throttling). When connections arrive on the proxy port — specifically those pending receipt of the PROXY protocol header — they are not properly counted against the server's configured maximum connection limit. This accounting flaw allows an unauthenticated remote attacker to open an unbounded number of connections through the proxy port, exhausting server resources and triggering a crash. No authentication, user interaction, or special privileges are required for exploitation (Red Hat CVE, MongoDB Jira).

Successful exploitation results in a denial of service (DoS) through server resource exhaustion, causing MongoDB to crash. The impact is limited to availability — there is no confidentiality or integrity impact, and no data exposure or lateral movement risk is associated with this vulnerability. Any service or application dependent on the affected MongoDB instance would become unavailable for the duration of the attack or until the server is restarted (Red Hat CVE).

There is no public proof-of-concept exploit and no evidence of active in-the-wild exploitation at this time. The vulnerability is network-exploitable with no authentication required and low attack complexity, making it straightforward to trigger if the proxy port is exposed. The EPSS score is approximately 0.04%, indicating a low current probability of exploitation. The CVE is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog. No threat actor attribution has been reported (Red Hat CVE, MongoDB Jira).

1. Reconnaissance: Identify MongoDB instances with the proxy port enabled and exposed to the network using port scanning tools (e.g., Nmap, Shodan), targeting the configured proxy listener port.
2. Establish connections: Initiate a large number of TCP connections to the MongoDB proxy port without sending the PROXY protocol header, keeping connections in a pending/half-open state.
3. Bypass connection counting: Because these pending proxy-port connections are not counted toward the server's total accepted connection limit, the attacker can open connections far exceeding the configured maximum.
4. Exhaust resources: Continue opening connections until server resources (file descriptors, memory, threads) are exhausted, causing MongoDB to crash and become unavailable (Red Hat CVE, MongoDB Jira).

• Network: Unusually high volume of TCP connections to the MongoDB proxy port from one or more source IPs; connections remaining in a SYN_RECV or ESTABLISHED state without completing the PROXY protocol handshake.
• Logs: MongoDB server logs showing a sudden spike in connection attempts on the proxy port; crash or unclean shutdown entries in MongoDB logs (mongod.log) coinciding with connection surges.
• Process: MongoDB process (mongod) terminating unexpectedly or restarting repeatedly; OS-level resource exhaustion indicators such as file descriptor limits being reached (e.g., ulimit errors in system logs).
• System: Operating system logs (e.g., /var/log/syslog, journalctl) showing out-of-resource errors or OOM (out-of-memory) events associated with the mongod process.

Upgrade MongoDB to the fixed versions: 7.0.29, 8.0.18, or 8.2.4 (MongoDB Jira). As an interim workaround, restrict network access to the MongoDB proxy port using firewall rules or network ACLs to allow only trusted proxy sources. Implement rate limiting on connections to the proxy port at the network or load-balancer level. Monitor connection counts and resource utilization on the proxy port for anomalous activity (Red Hat CVE).