Exposure of the message authentication key through the encryption keystream in the stream mode of IesEngine (an IesEngine constructed without a… (CVE-2026-16001)
CVE-2026-16001 is a vulnerability in the Legion of the Bouncy Castle Inc. bc-csharp library before version 2.7.0. It involves exposure of the message authentication key through the encryption keystream in the stream mode of IesEngine when constructed without a block cipher. An attacker who observes one encrypted message with known plaintext can forge shorter messages that the recipient accepts as authentic by exploiting the MAC key derivation flaw.
AI Analysis
Technical Summary
The vulnerability arises because the MAC key is derived directly from the key derivation output immediately after a keystream as long as the message. Since the derivation input depends only on the static key pair and fixed parameters, the keystream revealed by one known plaintext message contains the MAC key for all sufficiently shorter messages. This allows a remote attacker to craft ciphertext and MAC tags for forged messages that will be accepted as authentic by the recipient.
Potential Impact
A remote attacker who has observed one encrypted message with known plaintext can forge shorter messages of their choosing that the recipient will accept as authentic. This compromises message authenticity and integrity, potentially allowing unauthorized message injection or manipulation without detection.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or patch information is provided in the available data. Users should monitor for vendor updates and advisories regarding this vulnerability.
Exposure of the message authentication key through the encryption keystream in the stream mode of IesEngine (an IesEngine constructed without a… (CVE-2026-16001)
Description
CVE-2026-16001 is a vulnerability in the Legion of the Bouncy Castle Inc. bc-csharp library before version 2.7.0. It involves exposure of the message authentication key through the encryption keystream in the stream mode of IesEngine when constructed without a block cipher. An attacker who observes one encrypted message with known plaintext can forge shorter messages that the recipient accepts as authentic by exploiting the MAC key derivation flaw.
CVSS v4.0
Affected software
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability arises because the MAC key is derived directly from the key derivation output immediately after a keystream as long as the message. Since the derivation input depends only on the static key pair and fixed parameters, the keystream revealed by one known plaintext message contains the MAC key for all sufficiently shorter messages. This allows a remote attacker to craft ciphertext and MAC tags for forged messages that will be accepted as authentic by the recipient.
Potential Impact
A remote attacker who has observed one encrypted message with known plaintext can forge shorter messages of their choosing that the recipient will accept as authentic. This compromises message authenticity and integrity, potentially allowing unauthorized message injection or manipulation without detection.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or patch information is provided in the available data. Users should monitor for vendor updates and advisories regarding this vulnerability.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-43qj-h4fh-p2h4
- Osv Schema Version
- 1.4.0
- Aliases
- ["CVE-2026-16001"]
- Database Specific Severity
- HIGH
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6abfeebca43b0b3b89e56607
Added to database: 10/02/2026, 17:49:48 UTC
Last enriched: 10/02/2026, 18:22:53 UTC
Last updated: 10/02/2026, 18:45:56 UTC
Views: 2
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