CVE-2026-84969— Heap overflow via truncated base64 encoding of binary fields in length-limited JSON output
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 mongo-c-driver是美国MongoDB公司开源的一款C语言数据库驱动。 MongoDB mongo-c-driver 1.30.0版本至1.30.9之前版本和2.0.0版本至2.5.2之前版本存在缓冲区错误漏洞，该漏洞源于BSON到JSON转换辅助函数存在内存处理错误，可能导致在二进制字段编码且输出被调用者配置的长度限制截断时，向堆缓冲区末尾之外写入少量字节，从而使预期缓冲区之外的数据被少量修改。
Possible ATT&CK Techniques 1 AI
T1190 · Exploit Public-Facing Application
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I. Basic Information for CVE-2026-84969
Vulnerability Information
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Vulnerability Title
Heap overflow via truncated base64 encoding of binary fields in length-limited JSON output
Source: CVE Program / CVE List V5
Vulnerability Description
A memory-handling error in the BSON-to-JSON conversion helpers of the MongoDB C Driver can write a small number of bytes past the end of a heap buffer when a binary field is encoded and the output is cut short at a caller-configured length limit. A party who supplies the document content, with no privileges on the application that links the driver, may cause a small amount of data outside the intended buffer to be altered.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
跨界内存写
Source: CVE Program / CVE List V5
Vulnerability Title
MongoDB mongo-c-driver 缓冲区错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
MongoDB mongo-c-driver是美国MongoDB公司开源的一款C语言数据库驱动。 MongoDB mongo-c-driver 1.30.0版本至1.30.9之前版本和2.0.0版本至2.5.2之前版本存在缓冲区错误漏洞，该漏洞源于BSON到JSON转换辅助函数存在内存处理错误，可能导致在二进制字段编码且输出被调用者配置的长度限制截断时，向堆缓冲区末尾之外写入少量字节，从而使预期缓冲区之外的数据被少量修改。
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-2026-84969
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Vendor Pages for CVE-2026-84969 (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-2026-84963 | 5.3 MEDIUM | Silent field truncation via unchecked int cast of huge JSON string values in JSON-to-BSON |
| 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 |
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