CVE-2021-32785

NameCVE-2021-32785
Descriptionmod_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.
SourceCVE (at NVD; CERT, LWN, oss-sec, fulldisc, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)
ReferencesDLA-3409-1
Debian Bugs991583

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
libapache2-mod-auth-openidc (PTS)buster2.3.10.2-1+deb10u1vulnerable
buster (security)2.3.10.2-1+deb10u3fixed
bullseye (security), bullseye2.4.9.4-0+deb11u3fixed
bookworm2.4.12.3-2fixed
sid, trixie2.4.15.1-1fixed

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
libapache2-mod-auth-openidcsourcebuster2.3.10.2-1+deb10u2DLA-3409-1
libapache2-mod-auth-openidcsource(unstable)2.4.9-1991583

Notes

[stretch] - libapache2-mod-auth-openidc <no-dsa> (Minor issue)
https://github.com/zmartzone/mod_auth_openidc/security/advisories/GHSA-55r8-6w97-xxr4
https://github.com/zmartzone/mod_auth_openidc/commit/dc672688dc1f2db7df8ad4abebc367116017a449 (v2.4.9)

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