Summary
AEADs/ascon-aead: Plaintext exposed in decryptinplace_detached even on tag verification failure
In decrypt_in_place_detached, the decrypted ciphertext (which is the correct ciphertext) is exposed even if the tag is incorrect.
Details
This is because in decrypt_inplace in asconcore.rs, tag verification causes an error to be returned with the plaintext contents still in buffer. The root cause of this vulnerability is similar to https://github.com/RustCrypto/AEADs/security/advisories/GHSA-423w-p2w9-r7vq
PoC
use ascon_aead::Tag;
use ascon_aead::{Ascon128, Key, Nonce};
use ascon_aead::aead::{AeadInPlace, KeyInit};
fn main() {
let key = Key::<Ascon128>::from_slice(b"very secret key.");
let cipher = Ascon128::new(key);
let nonce = Nonce::<Ascon128>::from_slice(b"unique nonce 012"); // 128-bits; unique per message
let mut buffer: Vec<u8> = Vec::new(); // Buffer needs 16-bytes overhead for authentication tag
buffer.extend_from_slice(b"plaintext message");
// Encrypt `buffer` in-place detached, replacing the plaintext contents with ciphertext
cipher.encrypt_in_place_detached(nonce, b"", &mut buffer).expect("encryption failure!");
// Decrypt `buffer` in-place with the wrong tag, ignoring the decryption error
let _ = cipher.decrypt_in_place_detached(nonce, b"", &mut buffer, Tag::<Ascon128>::from_slice(b"\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"));
assert_eq!(&buffer, b"plaintext message");
}
Impact
If a program continues to use the result of decrypt_in_place_detached after a decryption failure, the result will be unauthenticated. This may permit some forms of chosen ciphertext attacks (CCAs).
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2025-27498? CVE-2025-27498 is a medium-severity security vulnerability in ascon_aead (rust), affecting versions <= 0.4.2. It is fixed in 0.4.3.
- Which versions of ascon_aead are affected by CVE-2025-27498? ascon_aead (rust) versions <= 0.4.2 is affected.
- Is there a fix for CVE-2025-27498? Yes. CVE-2025-27498 is fixed in 0.4.3. Upgrade to this version or later.
- Is CVE-2025-27498 exploitable, and should I be worried? Whether CVE-2025-27498 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2025-27498 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2025-27498? Upgrade
ascon_aeadto 0.4.3 or later.