CVE-2026-95105 PUBLISHED

Cloak AES-CTR cipher lacks ciphertext authentication, allowing chosen-plaintext forgery by bit flipping

Assigner: EEF
Reserved: 25.09.2026 Published: 06.10.2026 Updated: 06.10.2026

Reliance on Obfuscation or Encryption of Security-Relevant Inputs without Integrity Checking vulnerability in danielberkompas cloak allows an attacker with write access to stored ciphertext to make it decrypt to a chosen value via bit flipping.

Cloak.Ciphers.AES.CTR encrypts with AES-256 in CTR mode and stores the key tag, the IV and the ciphertext with no MAC. decrypt/2 checks only the key tag and the minimum length before it returns the plaintext, and Cloak.Ciphers.Deprecated.AES.CTR decrypts the legacy format the same way. CTR is a stream cipher, so a value XORed into the stored ciphertext is XORed into the plaintext at the same offset. An attacker who can write to the encrypted store (for example through SQL injection or a compromised replica) and who knows or can guess a stored plaintext can replace it with any value of the same length. The application receives that value with no error.

This issue affects cloak: from 0.1.0-pre onward.

Metrics

CVSS 4.0

CVSS 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
CVSS Score: 8.2

Exploitability Metrics		Vulnerable System Impact Metrics		Subsequent System Impact Metrics
Attack Vector	Network	Confidentiality	None	Confidentiality	None
Attack Complexity	Low	Integrity	High	Integrity	None
Attack Requirements	Present	Availability	None	Availability	None
Privileges Required	None
User Interaction	None

CVSS 4.0

Product Status

Vendor	danielberkompas
Product	cloak
Versions	Default: unaffected affected from 0.1.0-pre to * (excl.)

Vendor	danielberkompas
Product	cloak
Versions	Default: unaffected affected from 2bd17019e285b55c5c218cc842537bf9280f24c3 to * (excl.)

Workarounds

Configure the vault with Cloak.Ciphers.AES.GCM as the default cipher and re-encrypt existing values, for example with the cloak.migrate.ecto task from cloak_ecto. Then remove Cloak.Ciphers.AES.CTR and Cloak.Ciphers.Deprecated.AES.CTR from the vault configuration, so that ciphertext in the CTR format is no longer decrypted. AES-GCM authenticates the ciphertext and rejects modified values.

Credits

Peter Ullrich finder
Peter Ullrich reporter
Jonatan Männchen / EEF coordinator

References

Problem Types

CWE-649 Reliance on Obfuscation or Encryption of Security-Relevant Inputs without Integrity Checking CWE

Impacts

An attacker who can write to the encrypted store can set encrypted fields with known or guessable contents, such as roles, flags, or fixed-format records, to values of their choice without the key. The application decrypts and trusts the forged value.