CVE-2026-84963— Silent field truncation via unchecked int cast of huge JSON string values in JSON-to-BSON parser
Quick assessment
Affected
MongoDB C Driver
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.
MongoDB C Driver是美国MongoDB公司开源的一款C语言数据库驱动。 MongoDB C Driver 1.10.0至1.30.9之前版本和2.0.0至2.5.2之前版本存在数字错误漏洞，该漏洞源于JSON解析组件中的数值转换不正确，可能导致超长文本值被静默截断或字段被省略且解析操作仍报告成功，进而导致未经验证的攻击者利用该组件处理的数据与提交数据不一致，造成非预期数据修改。
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I. Basic Information for CVE-2026-84963
Vulnerability Information
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Vulnerability Title
Silent field truncation via unchecked int cast of huge JSON string values in JSON-to-BSON parser
Source: CVE Program / CVE List V5
Vulnerability Description
An incorrect numeric conversion in the JSON parsing component of the MongoDB C Driver's BSON library may cause an unusually large text value to be silently shortened, or the corresponding field to be omitted, while the parsing operation still reports success and returns no error. An unauthenticated party who can supply the input processed by an application that uses this component may cause that application to hold data that does not match what was submitted, which may result in unintended alteration of data.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
数值类型间的不正确转换
Source: CVE Program / CVE List V5
Vulnerability Title
MongoDB C Driver 数字错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
MongoDB C Driver是美国MongoDB公司开源的一款C语言数据库驱动。 MongoDB C Driver 1.10.0至1.30.9之前版本和2.0.0至2.5.2之前版本存在数字错误漏洞，该漏洞源于JSON解析组件中的数值转换不正确，可能导致超长文本值被静默截断或字段被省略且解析操作仍报告成功，进而导致未经验证的攻击者利用该组件处理的数据与提交数据不一致，造成非预期数据修改。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)
Affected Products
II. Public POCs for CVE-2026-84963
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Other References for CVE-2026-84963 (1)
Same Patch Batch · MongoDB · 2026-09-03 · 10 CVEs total
| CVE-2026-84971 | 6.5 MEDIUM | Persistent client crash loop via undersized FLE2 insert-update ciphertext in decryption pa |
| CVE-2026-84970 | 6.2 MEDIUM | Heap over-read or silent misparse via 32-bit truncation of JSON length in BSON JSON parser |
| CVE-2026-84964 | 5.9 MEDIUM | Heap corruption via OCSP request double free from crafted multi-URL certificate in TLS cli |
| CVE-2026-84968 | 5.3 MEDIUM | Heap out-of-bounds read via corrupt nested BSON in field path error message |
| CVE-2026-84965 | 5.1 MEDIUM | Heap write primitive via size round-up wrap during JSON parsing on 32-bit builds |
| CVE-2026-84966 | 5.1 MEDIUM | BSON element injection via NUL-embedded document keys in builder append |
| CVE-2026-84967 | 4.3 MEDIUM | Arbitrary command execution via shell-expanded connection string in Launch MongoDB Shell t |
| CVE-2026-84962 | 4.2 MEDIUM | Authenticated KMS request forgery via CRLF injection in GCP key identifier strings |
| CVE-2026-84969 | 3.7 LOW | Heap overflow via truncated base64 encoding of binary fields in length-limited JSON output |
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V. Comments for CVE-2026-84963
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