CVE-2021-23839
Incorrect SSLv2 rollback protection
Severity Score
Exploit Likelihood
Affected Versions
Public Exploits
0Exploited in Wild
-Decision
Descriptions
OpenSSL 1.0.2 supports SSLv2. If a client attempts to negotiate SSLv2 with a server that is configured to support both SSLv2 and more recent SSL and TLS versions then a check is made for a version rollback attack when unpadding an RSA signature. Clients that support SSL or TLS versions greater than SSLv2 are supposed to use a special form of padding. A server that supports greater than SSLv2 is supposed to reject connection attempts from a client where this special form of padding is present, because this indicates that a version rollback has occurred (i.e. both client and server support greater than SSLv2, and yet this is the version that is being requested). The implementation of this padding check inverted the logic so that the connection attempt is accepted if the padding is present, and rejected if it is absent. This means that such as server will accept a connection if a version rollback attack has occurred. Further the server will erroneously reject a connection if a normal SSLv2 connection attempt is made. Only OpenSSL 1.0.2 servers from version 1.0.2s to 1.0.2x are affected by this issue. In order to be vulnerable a 1.0.2 server must: 1) have configured SSLv2 support at compile time (this is off by default), 2) have configured SSLv2 support at runtime (this is off by default), 3) have configured SSLv2 ciphersuites (these are not in the default ciphersuite list) OpenSSL 1.1.1 does not have SSLv2 support and therefore is not vulnerable to this issue. The underlying error is in the implementation of the RSA_padding_check_SSLv23() function. This also affects the RSA_SSLV23_PADDING padding mode used by various other functions. Although 1.1.1 does not support SSLv2 the RSA_padding_check_SSLv23() function still exists, as does the RSA_SSLV23_PADDING padding mode. Applications that directly call that function or use that padding mode will encounter this issue. However since there is no support for the SSLv2 protocol in 1.1.1 this is considered a bug and not a security issue in that version. OpenSSL 1.0.2 is out of support and no longer receiving public updates. Premium support customers of OpenSSL 1.0.2 should upgrade to 1.0.2y. Other users should upgrade to 1.1.1j. Fixed in OpenSSL 1.0.2y (Affected 1.0.2s-1.0.2x).
OpenSSL versión 1.0.2 soporta SSLv2. Si un cliente intenta negociar SSLv2 con un servidor que está configurado para soportar tanto SSLv2 como versiones más recientes de SSL y TLS, entonces se hace una comprobación de un ataque de retroceso de versión cuando se deshace una firma RSA. Los clientes que soportan versiones de SSL o TLS superiores a SSLv2 deben usar una forma especial de relleno. Un servidor que soporta una versión superior a SSLv2 debe rechazar los intentos de conexión de un cliente en el que esté presente esta forma especial de relleno, porque esto indica que se ha producido un retroceso de versión (es decir, tanto el cliente como el servidor soportan una versión superior a SSLv2, y sin embargo esta es la versión que se está requiriendo). La implementación de esta comprobación de padding invirtió la lógica para que el intento de conexión sea aceptado si el padding está presente, y rechazado si está ausente. Esto significa que tal servidor aceptará una conexión si se ha producido un ataque de retroceso de versión. Además, el servidor rechazará erróneamente una conexión si se realiza un intento de conexión SSLv2 normal. Sólo los servidores OpenSSL versión 1.0.2 desde la versión 1.0.2s hasta la 1.0.2x están afectados por este problema. Para ser vulnerable, un servidor versión 1.0.2 debe 1) haber configurado la compatibilidad con SSLv2 en tiempo de compilación (está desactivada por defecto), 2) haber configurado la compatibilidad con SSLv2 en tiempo de ejecución (está deshabilitada por defecto), 3) haber configurado los ciphersuites de SSLv2 (no están en la lista de ciphersuites por defecto) OpenSSL versión 1.1.1 no presenta compatibilidad con SSLv2 y, por tanto, no es vulnerable a este problema. El error subyacente está en la implementación de la función RSA_padding_check_SSLv23(). Esto también afecta al modo de relleno RSA_SSLV23_PADDING usado por otras funciones. Aunque la versión 1.1.1 no soporta SSLv2, la función RSA_padding_check_SSLv23() sigue existiendo, al igual que el modo de relleno RSA_SSLV23_PADDING. Las aplicaciones que llamen directamente a esa función o utilicen ese modo de relleno se encontrarán con este problema. Sin embargo, como no existe soporte para el protocolo SSLv2 en la versión 1.1.1, esto se considera un error y no un problema de seguridad en esa versión. OpenSSL versión 1.0.2 está fuera de soporte y ya no recibe actualizaciones públicas. Los clientes de soporte Premium de OpenSSL versión 1.0.2 deben actualizar a la versión 1.0.2y. Los demás usuarios deben actualizar a la versión 1.1.1j. Corregido en OpenSSL versión 1.0.2y (Afectó versiones 1.0.2s-1.0.2x)
A flaw was found in openssl. OpenSSL 1.0.2 supports SSLv2. If a client attempts to negotiate SSLv2 with a server that is configured to support both SSLv2 and more recent SSL and TLS versions then a check is made for a version rollback attack when unpadding an RSA signature. However since there is no support for the SSLv2 protocol in 1.1.1 this is considered a bug and not a security issue in that version. OpenSSL 1.0.2 is out of support and no longer receiving public updates. Premium support customers of OpenSSL 1.0.2 should upgrade to 1.0.2y. Other users should upgrade to 1.1.1j. Fixed in OpenSSL 1.0.2y (Affected 1.0.2s-1.0.2x).
CVSS Scores
SSVC
- Decision:Track
Timeline
- 2021-01-12 CVE Reserved
- 2021-02-16 CVE Published
- 2024-06-22 EPSS Updated
- 2024-09-17 CVE Updated
- ---------- Exploited in Wild
- ---------- KEV Due Date
- ---------- First Exploit
CWE
- CWE-327: Use of a Broken or Risky Cryptographic Algorithm
CAPEC
References (12)
URL | Date | SRC |
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URL | Date | SRC |
---|---|---|
https://cert-portal.siemens.com/productcert/pdf/ssa-637483.pdf | 2024-06-21 | |
https://www.oracle.com//security-alerts/cpujul2021.html | 2024-06-21 | |
https://www.oracle.com/security-alerts/cpuApr2021.html | 2024-06-21 | |
https://www.oracle.com/security-alerts/cpuapr2022.html | 2024-06-21 | |
https://www.oracle.com/security-alerts/cpuoct2021.html | 2024-06-21 |
URL | Date | SRC |
---|---|---|
https://www.openssl.org/news/secadv/20210216.txt | 2024-06-21 | |
https://access.redhat.com/security/cve/CVE-2021-23839 | 2021-08-06 | |
https://bugzilla.redhat.com/show_bug.cgi?id=1930294 | 2021-08-06 |
Affected Vendors, Products, and Versions
Vendor | Product | Version | Other | Status | ||||||
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Vendor | Product | Version | Other | Status | <-- --> | Vendor | Product | Version | Other | Status |
Openssl Search vendor "Openssl" | Openssl Search vendor "Openssl" for product "Openssl" | >= 1.0.2s <= 1.0.2x Search vendor "Openssl" for product "Openssl" and version " >= 1.0.2s <= 1.0.2x" | - |
Affected
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Oracle Search vendor "Oracle" | Business Intelligence Search vendor "Oracle" for product "Business Intelligence" | 5.5.0.0.0 Search vendor "Oracle" for product "Business Intelligence" and version "5.5.0.0.0" | enterprise |
Affected
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Oracle Search vendor "Oracle" | Business Intelligence Search vendor "Oracle" for product "Business Intelligence" | 5.9.0.0.0 Search vendor "Oracle" for product "Business Intelligence" and version "5.9.0.0.0" | enterprise |
Affected
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Oracle Search vendor "Oracle" | Business Intelligence Search vendor "Oracle" for product "Business Intelligence" | 12.2.1.3.0 Search vendor "Oracle" for product "Business Intelligence" and version "12.2.1.3.0" | enterprise |
Affected
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Oracle Search vendor "Oracle" | Business Intelligence Search vendor "Oracle" for product "Business Intelligence" | 12.2.1.4.0 Search vendor "Oracle" for product "Business Intelligence" and version "12.2.1.4.0" | enterprise |
Affected
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Oracle Search vendor "Oracle" | Enterprise Manager For Storage Management Search vendor "Oracle" for product "Enterprise Manager For Storage Management" | 13.4.0.0 Search vendor "Oracle" for product "Enterprise Manager For Storage Management" and version "13.4.0.0" | - |
Affected
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Oracle Search vendor "Oracle" | Enterprise Manager Ops Center Search vendor "Oracle" for product "Enterprise Manager Ops Center" | 12.4.0.0 Search vendor "Oracle" for product "Enterprise Manager Ops Center" and version "12.4.0.0" | - |
Affected
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Oracle Search vendor "Oracle" | Graalvm Search vendor "Oracle" for product "Graalvm" | 19.3.5 Search vendor "Oracle" for product "Graalvm" and version "19.3.5" | enterprise |
Affected
| ||||||
Oracle Search vendor "Oracle" | Graalvm Search vendor "Oracle" for product "Graalvm" | 20.3.1.2 Search vendor "Oracle" for product "Graalvm" and version "20.3.1.2" | community |
Affected
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Oracle Search vendor "Oracle" | Graalvm Search vendor "Oracle" for product "Graalvm" | 21.0.0.2 Search vendor "Oracle" for product "Graalvm" and version "21.0.0.2" | community |
Affected
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Oracle Search vendor "Oracle" | Jd Edwards World Security Search vendor "Oracle" for product "Jd Edwards World Security" | a9.4 Search vendor "Oracle" for product "Jd Edwards World Security" and version "a9.4" | - |
Affected
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Oracle Search vendor "Oracle" | Zfs Storage Appliance Kit Search vendor "Oracle" for product "Zfs Storage Appliance Kit" | 8.8 Search vendor "Oracle" for product "Zfs Storage Appliance Kit" and version "8.8" | - |
Affected
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Siemens Search vendor "Siemens" | Sinec Ins Search vendor "Siemens" for product "Sinec Ins" | < 1.0 Search vendor "Siemens" for product "Sinec Ins" and version " < 1.0" | - |
Affected
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Siemens Search vendor "Siemens" | Sinec Ins Search vendor "Siemens" for product "Sinec Ins" | 1.0 Search vendor "Siemens" for product "Sinec Ins" and version "1.0" | - |
Affected
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Siemens Search vendor "Siemens" | Sinec Ins Search vendor "Siemens" for product "Sinec Ins" | 1.0 Search vendor "Siemens" for product "Sinec Ins" and version "1.0" | sp1 |
Affected
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