CVE-2021-32785

Format string bug in the Redis cache implementation

Severity Score

7.5

*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

*Multiple Sources

Exploited in Wild

*KEV

Decision

*SSVC

Descriptions

mod_auth_openidc is an authentication/authorization module for the Apache 2.x HTTP server that functions as an OpenID Connect Relying Party, authenticating users against an OpenID Connect Provider. When mod_auth_openidc versions prior to 2.4.9 are configured to use an unencrypted Redis cache (`OIDCCacheEncrypt off`, `OIDCSessionType server-cache`, `OIDCCacheType redis`), `mod_auth_openidc` wrongly performed argument interpolation before passing Redis requests to `hiredis`, which would perform it again and lead to an uncontrolled format string bug. Initial assessment shows that this bug does not appear to allow gaining arbitrary code execution, but can reliably provoke a denial of service by repeatedly crashing the Apache workers. This bug has been corrected in version 2.4.9 by performing argument interpolation only once, using the `hiredis` API. As a workaround, this vulnerability can be mitigated by setting `OIDCCacheEncrypt` to `on`, as cache keys are cryptographically hashed before use when this option is enabled.

mod_auth_openidc es un módulo de autenticación/autorización para el servidor HTTP Apache versión 2.x que funciona como OpenID Connect Relying Party, autenticando a usuarios contra un OpenID Connect Provider. Cuando mod_auth_openidc versiones anteriores a 2.4.9 están configuradas para usar una caché Redis no cifrada ("OIDCCacheEncrypt off", "OIDCSessionType server-cache", "OIDCCacheType redis"), "mod_auth_openidc" llevaba a cabo erróneamente la interpolación de argumentos antes de pasar las peticiones de Redis a "hiredis", que lo llevaría a cabo de nuevo y conlleva a un bug de cadena de formato no controlado. La evaluación inicial muestra que este bug no parece permitir ganar la ejecución de código arbitrario, pero puede provocar de forma fiable una denegación de servicio al bloquear repetidamente los trabajadores de Apache. Este bug se ha corregido en versión 2.4.9 al llevar a cabo la interpolación de argumentos sólo una vez, usando la API "hiredis". Como solución, esta vulnerabilidad puede ser mitigada ajustando "OIDCCacheEncrypt" a "on", ya que las claves de la caché son criptografiadas con hash antes de su uso cuando esta opción está activada

*Credits: N/A

CVSS Scores

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

Low

Attack Vector

Network

Attack Complexity

Medium

Authentication

None

Confidentiality

None

Integrity

None

Availability

Partial

* Common Vulnerability Scoring System

SSVC

Decision:-

Exploitation

Automatable

Tech. Impact

* Organization's Worst-case Scenario

Timeline

2021-05-12 CVE Reserved
2021-07-22 CVE Published
2024-08-03 CVE Updated
2024-08-08 EPSS Updated
---------- Exploited in Wild
---------- KEV Due Date
---------- First Exploit

CWE

CWE-134: Use of Externally-Controlled Format String

CAPEC

References (6)

URL	Tag	Source
https://github.com/zmartzone/mod_auth_openidc/releases/tag/v2.4.9	Release Notes
https://github.com/zmartzone/mod_auth_openidc/security/advisories/GHSA-55r8-6w97-xxr4	Mitigation
https://lists.debian.org/debian-lts-announce/2023/04/msg00034.html	Mailing List
https://security.netapp.com/advisory/ntap-20210902-0001	Third Party Advisory

URL	Date	SRC

URL	Date	SRC
https://github.com/zmartzone/mod_auth_openidc/commit/dc672688dc1f2db7df8ad4abebc367116017a449	2024-01-30
https://www.oracle.com/security-alerts/cpuapr2022.html	2024-01-30

URL	Date	SRC

Affected Vendors, Products, and Versions

Vendor		Product				Version		Other		Status
Vendor	Product	Version	Other	Status	<-- -->	Vendor	Product	Version	Other	Status
Openidc Search vendor "Openidc"	Mod Auth Openidc Search vendor "Openidc" for product "Mod Auth Openidc"	< 2.4.9 Search vendor "Openidc" for product "Mod Auth Openidc" and version " < 2.4.9"	-	Affected	in	Apache Search vendor "Apache"	Http Server Search vendor "Apache" for product "Http Server"	>= 2.0.0 <= 2.4.48 Search vendor "Apache" for product "Http Server" and version " >= 2.0.0 <= 2.4.48"	-	Safe
Netapp Search vendor "Netapp"		Cloud Backup Search vendor "Netapp" for product "Cloud Backup"				-		-		Affected
Debian Search vendor "Debian"		Debian Linux Search vendor "Debian" for product "Debian Linux"				10.0 Search vendor "Debian" for product "Debian Linux" and version "10.0"		-		Affected