CVE-2026-93394
libmongoc SCRAM client nonce-validation bypass
Description
A flaw in libmongoc's SCRAM authentication implementation caused the client to continue the authentication handshake and transmit the client proof even when a nonce mismatch was detected in the server's first message. An unauthorized party with a man-in-the-middle position could exploit this by injecting a crafted server-first-message containing a controlled salt and low iteration count, then capturing the resulting client proof to perform offline password cracking. This vulnerability is mitigated by TLS, which is standard in production deployments.
INFO
Published Date :
Sept. 17, 2026, 9:17 p.m.
Last Modified :
Sept. 17, 2026, 9:17 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | LOW | a39b4221-9bd0-4244-95fc-f3e2e07f1deb | ||||
| CVSS 3.1 | LOW | [email protected] | ||||
| CVSS 4.0 | MEDIUM | a39b4221-9bd0-4244-95fc-f3e2e07f1deb | ||||
| CVSS 4.0 | MEDIUM | [email protected] |
Solution
- Update libmongoc to the latest version.
- Ensure TLS is enabled for secure communication.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-93394.
| URL | Resource |
|---|---|
| https://jira.mongodb.org/browse/CDRIVER-6315 |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-93394 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-93394
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-93394 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-93394 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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New CVE Received by [email protected]
Sep. 17, 2026
Action Type Old Value New Value Added Description A flaw in libmongoc's SCRAM authentication implementation caused the client to continue the authentication handshake and transmit the client proof even when a nonce mismatch was detected in the server's first message. An unauthorized party with a man-in-the-middle position could exploit this by injecting a crafted server-first-message containing a controlled salt and low iteration count, then capturing the resulting client proof to perform offline password cracking. This vulnerability is mitigated by TLS, which is standard in production deployments. Added CVSS V4.0 AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CVSS V3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N Added CWE CWE-303 Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/93xxx/CVE-2026-93394.json">CVE-2026-93394</a> Added Reference https://jira.mongodb.org/browse/CDRIVER-6315