CVE-2026-16001
IesEngine stream-mode MAC forgery via length-dependent KDF split
Description
Exposure of the message authentication key through the encryption keystream in the stream mode of IesEngine (an IesEngine constructed without a block cipher) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote attacker who has observed one encrypted message with known plaintext to forge shorter messages of their choosing that the recipient accepts as authentic, via a crafted ciphertext and MAC tag, because the MAC key was taken from the key derivation output directly after a keystream as long as the message, while the derivation input depends only on the static key pair and fixed parameters. The keystream revealed by that one message therefore contains the MAC key for every sufficiently shorter message.
INFO
Published Date :
Oct. 2, 2026, 7:16 a.m.
Last Modified :
Oct. 27, 2026, 4:31 p.m.
Remotely Exploit :
Yes !
Source :
91579145-5d7b-4cc5-b925-a0262ff19630
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | HIGH | [email protected] | ||||
| CVSS 4.0 | HIGH | 91579145-5d7b-4cc5-b925-a0262ff19630 | ||||
| CVSS 4.0 | HIGH | 91579145-5d7b-4cc5-b925-a0262ff19630 |
Solution
- Update Bouncy Castle bc-csharp to version 2.7.0 or newer.
- Apply security patches or hotfixes if available.
- Review key derivation and MAC generation processes.
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-2026-16001.
| URL | Resource |
|---|---|
| https://github.com/bcgit/bc-csharp/commit/f881400b761134160ec2a05fd27c3e569453788d | Patch |
| https://github.com/bcgit/bc-csharp/wiki/CVE-2026-16001 | Patch Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-16001 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-2026-16001
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-2026-16001 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-16001 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.
-
Initial Analysis by [email protected]
Oct. 27, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N Added CPE Configuration OR *cpe:2.3:a:bouncycastle:bc-csharp:*:*:*:*:*:*:*:* versions up to (excluding) 2.7.0 Added Reference Type bcorg: https://github.com/bcgit/bc-csharp/commit/f881400b761134160ec2a05fd27c3e569453788d Types: Patch Added Reference Type bcorg: https://github.com/bcgit/bc-csharp/wiki/CVE-2026-16001 Types: Patch, Vendor Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Oct. 02, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-16001', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-10-02T17:54:38.625547Z'} -
New CVE Received by 91579145-5d7b-4cc5-b925-a0262ff19630
Oct. 02, 2026
Action Type Old Value New Value Added Description Exposure of the message authentication key through the encryption keystream in the stream mode of IesEngine (an IesEngine constructed without a block cipher) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote attacker who has observed one encrypted message with known plaintext to forge shorter messages of their choosing that the recipient accepts as authentic, via a crafted ciphertext and MAC tag, because the MAC key was taken from the key derivation output directly after a keystream as long as the message, while the derivation input depends only on the static key pair and fixed parameters. The keystream revealed by that one message therefore contains the MAC key for every sufficiently shorter message. Added CVSS V4.0 AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/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 CWE CWE-354 Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/16xxx/CVE-2026-16001.json">CVE-2026-16001</a> Added Reference https://github.com/bcgit/bc-csharp/commit/f881400b761134160ec2a05fd27c3e569453788d Added Reference https://github.com/bcgit/bc-csharp/wiki/CVE-2026-16001