CVE-2026-95105
Received Received - Intake

Authentication Bypass via Ciphertext Bit Flipping in Cloak

Publication date: 2026-10-06

Last updated on: 2026-10-06

Assigner: EEF

Description
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.

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Meta Information

Published
2026-10-06
Last Modified
2026-10-06
Generated
2026-10-06
AI Q&A
2026-10-06
EPSS Evaluated
N/A
NVD
CVE-2026-95105
EUVD
EUVD-2026-93090

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
danielberkompas cloak 0.1.0-pre
danielberkompas cloak 2bd17019e285b55c5c218cc842537bf9280f24c3

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-649 The product uses obfuscation or encryption of inputs that should not be mutable by an external actor, but the product does not use integrity checks to detect if those inputs have been modified.

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Executive Summary

This vulnerability involves the Cloak library's AES-CTR cipher implementation lacking ciphertext authentication. An attacker with write access to stored ciphertext can manipulate it via bit flipping. Since CTR mode is a stream cipher, modifying the ciphertext changes the decrypted plaintext predictably. The application decrypts and trusts the forged value without detecting tampering.

Detection Guidance

Detecting this vulnerability requires checking if your system uses the vulnerable Cloak library versions (0.1.0-pre or later) with AES-CTR cipher. Inspect Elixir application dependencies for cloak versions and configuration files for AES-CTR cipher usage. No direct network detection commands exist, but you can audit code and configurations.

Impact Analysis

An attacker could alter encrypted data to change its decrypted value to something malicious or unauthorized. For example, if the ciphertext is stored in a database, an attacker with write access could modify it to inject false data or escalate privileges. The application would process this tampered data without detecting the change.

Compliance Impact

This vulnerability could lead to unauthorized data tampering, violating integrity requirements in GDPR and HIPAA. GDPR mandates data integrity and security, while HIPAA requires protection against unauthorized alteration. Exploiting this flaw could result in non-compliance, potential fines, and loss of trust in data handling practices.

Mitigation Strategies
  • Switch from AES-CTR to AES-GCM cipher in the Cloak library configuration to enable ciphertext authentication.
  • Re-encrypt all existing data using the new AES-GCM cipher to ensure integrity protection.
  • Remove the vulnerable AES-CTR cipher configurations from your application settings.

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