Use-After-Free in MongoDB Server JavaScript Support for Aggregation Leads to Information Disclosure
- Exploited
- No known exploitation
- Fix
- Fixed in 8.3.16, 8.0.37, 7.0.48
- Who is exposed
- Not reported
Do first: Upgrade to a fixed version: 8.3.16, 8.0.37, 7.0.48.
- Last modified
- Whether it needs action now or is a reference record, by fixed rules, with why. Last checked is when cve.now last re-read it.What do these mean? →
- Reference
- Last checked
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 27/100 · provisional
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
A use-after-free flaw in the server-side JavaScript support for aggregation in MongoDB Server lets an attacker with low privileges (authenticated, with minimal or no assigned roles) read adjacent process memory remotely over the normal network protocol by sending a single crafted aggregation request. The leaked memory can include data that weakens memory-layout randomization, and in some cases the bug can also disrupt server availability.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
Read the original description
A use-after-free weakness in MongoDB Server's server-side JavaScript support for aggregation may allow a stale reference to previously freed process memory to be read and returned. An authenticated user with minimal or no assigned roles can trigger this condition over the normal network protocol by submitting a single crafted aggregation request, with no additional privileges or non-default configuration. Successful triggering this issue may result in adjacent process memory contents being returned, including data that undermines memory-layout randomization, and may in some cases affect server availability.
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure3/25Reachable over the network · Unknown: No advisory context yet
- Reach17/20Affects MongoDB (a widely deployed server, runtime, framework or database)
- Severity7.1/10CVSS 7.1
- No patch0/5No signal
What would change the score
- Would score about 82 if added to CISA KEV
- Would score about 77 if CISA's SSVC rates exploitation active
- Would score about 46 if advisories confirm default setups are exposed
What to do
Upgrade to a fixed version: 8.3.16, 8.0.37, 7.0.48.
Check your systems with an agent
Paste this into a coding or ops agent. It checks your systems read-only and reports a table per asset.
Check whether my systems are affected by CVE-2026-120818 (Use-After-Free in MongoDB Server JavaScript Support for Aggregation Leads to Information Disclosure), 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-2026-120818 (entry last updated 2026-11-10): Affected: - MongoDB MongoDB Server: 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 Fixed versions: 8.3.16, 8.0.37, 7.0.48. Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory. CISA KEV: CVE-2026-120818 is not listed as of cve.now's last read. This KEV status is for CVE-2026-120818 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-135727 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-2026-120818 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-2026-120818.
Timeline
- CVE published
- First seen by cve.now1 day
- Posted on X by cve.now
Affected versions
- MongoDB MongoDB Server
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
Evidence 3
Vendor advisory · 1
Establishes: Affected and fixed versions.
- Link
CVE record · 2
Establishes: The identifier and description.
- Record
- Record
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-120818
Is CVE-2026-120818 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: cve.now feed data
Which versions are affected by CVE-2026-120818?
MongoDB Server: from 8.3.0 before 8.3.16; from 8.0.0 before 8.0.37; from 7.0.0 before 7.0.48.Source: cve.now feed data
How do I fix CVE-2026-120818?
Upgrade to a fixed version: 8.3.16, 8.0.37, 7.0.48.Source: cve.now feed data