CVE-2026-126792
Published:November 12, 2026
Updated:November 13, 2026
A memory-safety flaw in the key-management request-building component of the library can lead to an out-of-bounds write on the heap. A fixed-size output buffer is used under an assumption about cryptographic key size that is never validated, so when the library is embedded by a caller that supplies its own cryptographic callback implementation, data larger than the buffer can be written past its end. Exploitation requires the ability to control the embedding application's in-process key-management provider configuration, a high-privilege position. The demonstrated impact is memory corruption resulting in abnormal termination of the client process.
Affected Packages
https://github.com/mongodb/libmongocrypt.git (GITHUB):
Affected version(s) >=pymongocrypt-1.1.0 <pymongocrypt-1.21.3Fix Suggestion:
Update to version pymongocrypt-1.21.3pymongocrypt (PYTHON):
Affected version(s) >=1.1.0 <1.21.3Fix Suggestion:
Update to version 1.21.3Related Resources (2)
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Contact UsCVSS v4
Base Score:
5.6
Attack Vector
LOCAL
Attack Complexity
HIGH
Attack Requirements
PRESENT
Privileges Required
HIGH
User Interaction
NONE
Vulnerable System Confidentiality
NONE
Vulnerable System Integrity
LOW
Vulnerable System Availability
HIGH
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
4.7
Attack Vector
LOCAL
Attack Complexity
HIGH
Privileges Required
HIGH
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
LOW
Availability
HIGH
Weakness Type (CWE)
Out-of-bounds Write