Vulnerability · Published Jul 22, 2021 · Assigned by GitHub_M
CVE-2021-32785Format string bug in the Redis cache implementation
Medium 5.3
In plain English
A medium-severity security flaw in mod_auth_openidc from zmartzone. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 2.7% (higher than 86% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | libapache2-mod-auth-openidc | 2.4.9-1 | DEBIAN-CVE-2021-32785 |
| Debian:13 | libapache2-mod-auth-openidc | 2.4.9-1 | DEBIAN-CVE-2021-32785 |
| Debian:14 | libapache2-mod-auth-openidc | 2.4.9-1 | DEBIAN-CVE-2021-32785 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| zmartzone | mod_auth_openidc | < 2.4.9 |
Weakness: CWE-134 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
References
- https://github.com/zmartzone/mod_auth_openidc/security/advisories/GHSA-55r8-6w97-xxr4
- https://github.com/zmartzone/mod_auth_openidc/commit/dc672688dc1f2db7df8ad4abebc367116017a449
- https://github.com/zmartzone/mod_auth_openidc/releases/tag/v2.4.9
- https://www.oracle.com/security-alerts/cpuapr2022.html
- https://security.netapp.com/advisory/ntap-20210902-0001/
- [debian-lts-announce] 20230430 [SECURITY] [DLA 3409-1] libapache2-mod-auth-openidc security update mailing-list