CVE-2026-16001

8.2 HIGH 0.2% exploit odds Fix listed Other

What it is

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.

At a glance

Exploitability: Can be exploited over the network without logging in. High risk of data tampering.
Exploit odds: 0.2% chance of exploitation in the next 30 days (EPSS).
Fix: A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

2026-07-16 23:53 UTC ReservedThe CVE id was reserved by its CNA
2026-10-02 07:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2026-10-27 16:31 UTC Last updatedMost recent change to the record

Why it ranks here

Exploited in the wild: no, CISA does not list it.
Exploit odds: 0.2% in the next 30 days (EPSS).
Severity: 8.2 HIGH (CVSS).
Fix: a patch or advisory is linked.

Details

Published: 2026-10-02 07:16 UTC
Last modified: 2026-10-27 16:31 UTC
Exploit probability: 0.2% · EPSS, next 30 days
Weakness: CWE-354
Record status: Analyzed

Affected

Bouncycastle bc-csharp < 2.7.0

Attack profile CVSS 4.0 · 8.2

Attack vector: Network
Complexity: Low
Attack requirements: Present
Privileges needed: None
User interaction: None
Confidentiality: None
Integrity: High
Availability: None

Raw vector

CVSS:4.0/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

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-16001.md and follow it. Check whether this project is affected by CVE-2026-16001. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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Fix and advisories

References

NVD record · CVE.org record