{"id":"EEF-CVE-2026-95105","summary":"Cloak AES-CTR cipher lacks ciphertext authentication, allowing chosen-plaintext forgery by bit flipping","details":"## Summary\n\nReliance 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.\n\n`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.\n\nThis issue affects cloak: from 0.1.0-pre onward.\n\n## Proof of concept\n\n1. Encrypt `\"role=user \"` with `Cloak.Ciphers.AES.CTR.encrypt/2` and a random 32-byte key.\n2. Without the key, XOR the last 10 bytes of the result (the ciphertext body) with `:crypto.exor(\"role=user \", \"role=admin\")`. Leave the key tag and the IV unchanged.\n3. Call `Cloak.Ciphers.AES.CTR.decrypt/2` on the modified value. It returns `{:ok, \"role=admin\"}`.\n\n## Impact\n\nAn 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.\n\n## Workarounds\n\nConfigure 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.","aliases":["CVE-2026-95105"],"modified":"2026-10-06T08:45:03.181687744Z","published":"2026-10-06T08:37:56.987Z","database_specific":{"cwe_ids":["CWE-649"],"capec_ids":["CAPEC-39"],"cpe_ids":["cpe:2.3:a:danielberkompas:cloak:*:*:*:*:*:*:*:*"]},"references":[{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-95105.html"},{"type":"WEB","url":"https://github.com/danielberkompas/cloak/commit/2bd17019e285b55c5c218cc842537bf9280f24c3"},{"type":"PACKAGE","url":"https://hex.pm/packages/cloak"}],"affected":[{"package":{"name":"cloak","ecosystem":"Hex","purl":"pkg:hex/cloak"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0.1.0-pre"}]}],"versions":["0.1.0","0.1.0-pre","0.2.0","0.2.1","0.2.2","0.3.1","0.3.2","0.3.3","0.4.0","0.5.0","0.6.0","0.6.1","0.6.2","0.7.0","0.7.0-alpha.1","0.7.0-alpha.2","0.8.0","0.9.0","0.9.1","0.9.2","1.0.0","1.0.0-alpha.0","1.0.1","1.0.2","1.0.3","1.1.0","1.1.1","1.1.2","1.1.3","1.1.4"],"database_specific":{"source":"https://cna.erlef.org/osv/EEF-CVE-2026-95105.json"}},{"ranges":[{"type":"GIT","repo":"https://github.com/danielberkompas/cloak","events":[{"introduced":"2bd17019e285b55c5c218cc842537bf9280f24c3"}]}],"versions":["v1.1.4","v1.1.3","v1.1.2","v1.1.1","v1.1.0","v1.0.3","v1.0.2","v1.0.1","v1.0.0","v1.0.0-alpha.0","v0.9.2","v0.9.1","v0.9.0","v0.8.0","v0.7.0","v0.7.0-alpha.2","v0.7.0-alpha.1","v0.6.2","v0.6.1","v0.6.0","v0.5.0","v0.4.0","v0.3.3","v0.3.2","v0.3.0","v0.2.3","v0.2.2","v0.2.1","v0.2.0","v0.1.0","v0.1.0-pre"],"database_specific":{"source":"https://cna.erlef.org/osv/EEF-CVE-2026-95105.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"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"}],"credits":[{"name":"Peter Ullrich","type":"FINDER"},{"name":"Peter Ullrich","type":"REPORTER"},{"name":"Jonatan Männchen / EEF","type":"COORDINATOR"}]}