CVE-2026-16001

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.

CVSS v3 7.5 HIGH

7.5^/10

CVSS v3 : HIGH

Vector :

Exploitability : 3.9 / Impact : 3.6

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact HIGH

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://github.com/bcgit/bc-csharp/commit/f881400b761134160ec2a05fd27c3e569453788d	Patch
https://github.com/bcgit/bc-csharp/wiki/CVE-2026-16001	Patch Vendor Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:bouncycastle:bc-csharp:*:*:*:*:*:*:*:*

History

27 Oct 2026, 16:31

Type	Values Removed	Values Added
CVSS	v2 : ~~unknown~~ v3 : ~~unknown~~	v2 : unknown v3 : 7.5
CPE		cpe:2.3:a:bouncycastle:bc-csharp::::::::
First Time		Bouncycastle bc-csharp Bouncycastle
References	~~() https://github.com/bcgit/bc-csharp/commit/f881400b761134160ec2a05fd27c3e569453788d -~~	() https://github.com/bcgit/bc-csharp/commit/f881400b761134160ec2a05fd27c3e569453788d - Patch
References	~~() https://github.com/bcgit/bc-csharp/wiki/CVE-2026-16001 -~~	() https://github.com/bcgit/bc-csharp/wiki/CVE-2026-16001 - Patch, Vendor Advisory

02 Oct 2026, 07:16

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-10-02 07:16

Updated : 2026-10-27 16:31

NVD link : CVE-2026-16001

Mitre link : CVE-2026-16001

CVE.ORG link : CVE-2026-16001

JSON object : View

Products Affected

bouncycastle

bc-csharp

CWE

CWE-354

Improper Validation of Integrity Check Value

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