CVE-2021-32785: Format string bug in the Redis cache implementation
First published: Thu Jul 22 2021(Updated: )
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.
Credit: security-advisories@github.com security-advisories@github.com
| Affected Software | Affected Version | How to fix |
|---|---|---|
| Openidc Mod Auth Openidc | <2.4.9 | |
| Apache HTTP server | >=2.0.0<=2.4.48 | |
| All of | ||
| Openidc Mod Auth Openidc | <2.4.9 | |
| Apache HTTP server | >=2.0.0<=2.4.48 | |
| Netapp Cloud Backup | ||
| Debian Debian Linux | =10.0 |
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Reference Links
- https://github.com/zmartzone/mod_auth_openidc/commit/dc672688dc1f2db7df8ad4abebc367116017a449
- https://github.com/zmartzone/mod_auth_openidc/releases/tag/v2.4.9
- https://github.com/zmartzone/mod_auth_openidc/security/advisories/GHSA-55r8-6w97-xxr4
- https://lists.debian.org/debian-lts-announce/2023/04/msg00034.html
- https://security.netapp.com/advisory/ntap-20210902-0001/
- https://www.oracle.com/security-alerts/cpuapr2022.html
Frequently Asked Questions
What is CVE-2021-32785?
CVE-2021-32785 is a vulnerability in mod_auth_openidc version prior to 2.4.9 that allows an attacker to perform unauthorized actions.
What is mod_auth_openidc?
mod_auth_openidc is an authentication/authorization module for the Apache 2.x HTTP server that functions as an OpenID Connect Relying Party.
How does CVE-2021-32785 affect mod_auth_openidc?
CVE-2021-32785 affects mod_auth_openidc versions prior to 2.4.9 by allowing an attacker to exploit an unencrypted Redis cache.
What is the severity of CVE-2021-32785?
CVE-2021-32785 has a severity rating of high (7.5).
How can I fix CVE-2021-32785?
To fix CVE-2021-32785, upgrade mod_auth_openidc to version 2.4.9 or later.
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