VulnerabilityPublished 17 Sep 2026

CVE-2026-93395: MongoDB C Driver · Integer Underflow

Affects MongoDB C DriverSource CVE Database V5

Compare

Not known to be exploited · CVSS 6.9 Medium : upgrade to 2.3.1 when convenient.

Data as of 1 Nov 2026, 22:58 UTC

CVSS 4.0 base score

6.9Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.4% chance of exploitation in 30 days – higher than 34% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 2.3.1

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: None
User Interaction: None
Vulnerable system confidentiality: None
Vulnerable system integrity: None
Vulnerable system availability: Low
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: None: There is no loss of confidentiality within the Vulnerable System.
Vulnerable system integrity: None: There is no loss of integrity within the Vulnerable System.
Vulnerable system availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the Vulnerable System are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 17 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 1 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

ghsa-jm9m-v7jc-m4j8

What to do

Upgrade MongoDB C Driver to 2.3.1.

Affected software

Product	Affected	Fixed in
MongoDB Inc.C Driver	Affected >=2.0.0 <2.3.1	Fixed in 2.3.1

AI-suggested

No explicit patch or remediation is stated in the provided data. If you cannot patch yet, applications should avoid processing untrusted BSON input or implement input validation to ensure BSON document lengths meet minimum size requirements.

Description

CVE-2026-93395 is an integer underflow vulnerability in the bson_new_from_buffer() function of the MongoDB C Driver. The function fails to validate that the BSON document length is at least 5 bytes, allowing a zero-length prefix to cause an integer wraparound. This leads to a heap out-of-bounds read and a process crash, resulting in a denial of service. The vulnerability affects versions from 2.0.0 up to but not including 2.3.1. No known exploits are reported in the wild. The CVSS 4.0 score is 6.9, indicating a medium severity.

Impact

An attacker who can supply specially crafted BSON data to an application using the vulnerable MongoDB C Driver versions can cause the application to crash due to a heap out-of-bounds read triggered by an integer underflow. This results in a denial of service condition. There is no indication of privilege escalation, data corruption, or remote code execution from the provided data.

Summary

The vulnerability arises from missing lower-bound validation in the bson_new_from_buffer() function within libbson, part of the MongoDB C Driver. Specifically, the function reads a 32-bit document length from the input buffer without verifying it meets the minimum BSON document size of 5 bytes. When the length is zero, the check for the document's null terminator causes an integer underflow, wrapping to UINT32_MAX. This results in a heap out-of-bounds read that crashes the process. An attacker able to supply crafted BSON input to an application using this API can trigger a denial of service by crashing the process.

References

jira.mongodb.org/browse/CDRIVER-6343 (opens in a new tab)

Community reviews

Loading reviews…

Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 25 Sep 2026, 04:19 UTC

WeaknessesCWE-191

Technical details

References

Community reviews

Related threats