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CVE-2021-32785— Format string bug in the Redis cache implementation

Quick assessment

Affected
zmartzone mod_auth_openidc
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Apache HTTP Server是美国阿帕奇（Apache）基金会的一款开源网页服务器。该服务器具有快速、可靠且可通过简单的API进行扩充的特点。 Apache 2.4.9之前版本存在格式化字符串错误漏洞，攻击者可以通过反复使Apache工作程序崩溃来可靠地引发拒绝服务。

CVSS 5.3 · Medium EPSS 2.73% · P85

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application
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I. Basic Information for CVE-2021-32785

Vulnerability Information
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Vulnerability Title
Format string bug in the Redis cache implementation
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Source: CVE Program / CVE List V5
Vulnerability Type
使用外部控制的格式字符串
Source: CVE Program / CVE List V5
Vulnerability Title
Apache HTTP Server 格式化字符串错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Apache HTTP Server是美国阿帕奇（Apache）基金会的一款开源网页服务器。该服务器具有快速、可靠且可通过简单的API进行扩充的特点。 Apache 2.4.9之前版本存在格式化字符串错误漏洞，攻击者可以通过反复使Apache工作程序崩溃来可靠地引发拒绝服务。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
zmartzone mod_auth_openidc < 2.4.9 -

II. Public POCs for CVE-2021-32785

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III. Intelligence Information for CVE-2021-32785

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Patches & Fixes for CVE-2021-32785 (1)

Vendor Advisories for CVE-2021-32785 (2)

Mailing List Discussions for CVE-2021-32785 (1)

Other References for CVE-2021-32785 (1)

IV. Related Vulnerabilities

Same product: mod_auth_openidc
Same vendor: zmartzone
Same weakness: CWE-134

V. Comments for CVE-2021-32785

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