Описание
Issue summary: The implementations of AES-SIV (RFC 5297) and AES-GCM-SIV
(RFC 8452) mishandle the authentication of AAD (Additional Authenticated
Data) with an empty ciphertext allowing a forgery of such messages.
Impact summary: An attacker can forge empty messages with arbitrary AAD
to the victim's application using these ciphers.
AES-SIV (RFC 5297) and AES-GCM-SIV (RFC 8452) are nonce-misuse-resistant AEAD
modes: they accept a key, nonce, optional AAD (bytes that are authenticated
but not encrypted), and plaintext, and produces ciphertext plus a 16-byte
tag. On decrypt, EVP_DecryptFinal_ex() is documented to return success only
if the tag is verified succesfully.
In OpenSSL's provider implementation of these ciphers, the expected tag is
computed only when decryption function is invoked with non-empty data.
If the caller supplies AAD and then calls EVP_DecryptFinal_ex() without
invocation of the ciphertext update, which can happen when the received
ciphertext length is zero, the tag is never recalculated and still holds its
all-zeros value.
When AES-GCM-SIV is used, an attacker who sends arbitrary AAD, empty
ciphertext, and all-zeros tag passes authentication under any key they do not
know, single-shot. When AES-SIV is used, for mounting the attack it's
necessary for the application to reuse the decryption context without
resetting the key.
AES-SIV is implemented since OpenSSL 3.0. AES-GCM-SIV is implemented since
OpenSSL 3.2.
No protocols implemented in OpenSSL itself (TLS/CMS/PKCS7/HPKE/QUIC) support
either AES-GCM-SIV or AES-SIV. To mount an attack, the applications must
implement their own protocol and use the EVP interface. Also they must skip the
ciphertext update when a message with an empty ciphertext arrives.
The FIPS modules in 4.0, 3.6, 3.5, 3.4, and 3.0 are not affected by this
issue, as these algorithms are not FIPS approved and the affected code is
outside the OpenSSL FIPS module boundary.
A flaw was found in OpenSSL. The implementations of AES-SIV (Advanced Encryption Standard - SIV) and AES-GCM-SIV (Advanced Encryption Standard - Galois/Counter Mode - SIV) incorrectly process authentication tags for empty messages. This vulnerability allows a remote attacker to forge empty messages with arbitrary Additional Authenticated Data (AAD) in applications that utilize these specific cipher modes within custom protocols and do not properly handle zero-length ciphertexts. This could lead to unauthorized data manipulation.
Отчет
This flaw is rated as Low impact. It affects applications that utilize OpenSSL's AES-SIV or AES-GCM-SIV modes within custom protocols and specifically mishandle empty ciphertexts. Standard OpenSSL protocols, such as TLS, are not affected. Successful exploitation requires an application to use the EVP interface and to skip ciphertext updates when processing zero-length ciphertexts, representing an uncommon and non-default configuration.
Меры по смягчению последствий
The vulnerability arises from specific application implementations using OpenSSL's AES-SIV or AES-GCM-SIV modes with custom protocols and an atypical handling of empty ciphertexts. As this scenario is not a default or commonly deployed configuration in Red Hat products, and no direct configuration or operational control exists to mitigate this specific flaw without patching, the following applies: Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Затронутые пакеты
| Платформа | Пакет | Состояние | Рекомендация | Релиз |
|---|---|---|---|---|
| Red Hat Enterprise Linux 10 | edk2 | Fix deferred | ||
| Red Hat Enterprise Linux 10 | shim | Fix deferred | ||
| Red Hat Enterprise Linux 10 | shim-unsigned-aarch64 | Fix deferred | ||
| Red Hat Enterprise Linux 10 | shim-unsigned-x64 | Fix deferred | ||
| Red Hat Enterprise Linux 6 | openssl | Not affected | ||
| Red Hat Enterprise Linux 7 | ovmf | Not affected | ||
| Red Hat Enterprise Linux 8 | compat-openssl10 | Not affected | ||
| Red Hat Enterprise Linux 8 | edk2 | Not affected | ||
| Red Hat Enterprise Linux 8 | mingw-openssl | Not affected | ||
| Red Hat Enterprise Linux 8 | openssl | Not affected |
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Дополнительная информация
Статус:
EPSS
3.7 Low
CVSS3
Связанные уязвимости
Issue summary: The implementations of AES-SIV (RFC 5297) and AES-GCM-SIV (RFC 8452) mishandle the authentication of AAD (Additional Authenticated Data) with an empty ciphertext allowing a forgery of such messages. Impact summary: An attacker can forge empty messages with arbitrary AAD to the victim's application using these ciphers. AES-SIV (RFC 5297) and AES-GCM-SIV (RFC 8452) are nonce-misuse-resistant AEAD modes: they accept a key, nonce, optional AAD (bytes that are authenticated but not encrypted), and plaintext, and produces ciphertext plus a 16-byte tag. On decrypt, `EVP_DecryptFinal_ex()` is documented to return success only if the tag is verified succesfully. In OpenSSL's provider implementation of these ciphers, the expected tag is computed only when decryption function is invoked with non-empty data. If the caller supplies AAD and then calls `EVP_DecryptFinal_ex()` without invocation of the ciphertext update, which can happen when the received ciphertext length is zero, t...
Issue summary: The implementations of AES-SIV (RFC 5297) and AES-GCM-SIV (RFC 8452) mishandle the authentication of AAD (Additional Authenticated Data) with an empty ciphertext allowing a forgery of such messages. Impact summary: An attacker can forge empty messages with arbitrary AAD to the victim's application using these ciphers. AES-SIV (RFC 5297) and AES-GCM-SIV (RFC 8452) are nonce-misuse-resistant AEAD modes: they accept a key, nonce, optional AAD (bytes that are authenticated but not encrypted), and plaintext, and produces ciphertext plus a 16-byte tag. On decrypt, `EVP_DecryptFinal_ex()` is documented to return success only if the tag is verified succesfully. In OpenSSL's provider implementation of these ciphers, the expected tag is computed only when decryption function is invoked with non-empty data. If the caller supplies AAD and then calls `EVP_DecryptFinal_ex()` without invocation of the ciphertext update, which can happen when the received ciphertext length is zero, t
Incorrect Tag Processing for Empty Messages in AES-GCM-SIV and AES-SIV modes
Issue summary: The implementations of AES-SIV (RFC 5297) and AES-GCM-S ...
Issue summary: The implementations of AES-SIV (RFC 5297) and AES-GCM-SIV (RFC 8452) mishandle the authentication of AAD (Additional Authenticated Data) with an empty ciphertext allowing a forgery of such messages. Impact summary: An attacker can forge empty messages with arbitrary AAD to the victim's application using these ciphers. AES-SIV (RFC 5297) and AES-GCM-SIV (RFC 8452) are nonce-misuse-resistant AEAD modes: they accept a key, nonce, optional AAD (bytes that are authenticated but not encrypted), and plaintext, and produces ciphertext plus a 16-byte tag. On decrypt, `EVP_DecryptFinal_ex()` is documented to return success only if the tag is verified succesfully. In OpenSSL's provider implementation of these ciphers, the expected tag is computed only when decryption function is invoked with non-empty data. If the caller supplies AAD and then calls `EVP_DecryptFinal_ex()` without invocation of the ciphertext update, which can happen when the received ciphertext length is zero...
EPSS
3.7 Low
CVSS3