HOMEVULNERABILITIESCVE-2021-32785
HIGH

CVE-2021-32785

CWE-134Published: July 22, 2021· Updated: Jun 17, 2026

7.5
CVSS v3.1

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.

NVD Source

Technical Analysis

CVE-2021-32785 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

A successful exploit results in availability disruption (denial of service), with a CVSS base score of 7.5.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorNetwork
Attack ComplexityLow
Privileges Req.None
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityNone
IntegrityNone
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected Vendors & Products

Apache1 product(s)
http server
Debian1 product(s)
debian linux
netapp1 product(s)
cloud backup
openidc1 product(s)
mod auth openidc
Source: NVD CPE · 4 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
External links open in a new tab. Always verify in a controlled environment before use.

Official Patches & Advisories

PATCHhttps://github.com/zmartzone/mod_auth_openidc/commit/dc672688dc1f2db7df8ad4abebc367116017a449
PATCHhttps://www.oracle.com/security-alerts/cpuapr2022.html
PATCHhttps://github.com/zmartzone/mod_auth_openidc/commit/dc672688dc1f2db7df8ad4abebc367116017a449
PATCHhttps://www.oracle.com/security-alerts/cpuapr2022.html
ADVISORYhttps://github.com/zmartzone/mod_auth_openidc/releases/tag/v2.4.9
ADVISORYhttps://github.com/zmartzone/mod_auth_openidc/security/advisories/GHSA-55r8-6w97-xxr4
ADVISORYhttps://lists.debian.org/debian-lts-announce/2023/04/msg00034.html
ADVISORYhttps://security.netapp.com/advisory/ntap-20210902-0001/
ADVISORYhttps://github.com/zmartzone/mod_auth_openidc/releases/tag/v2.4.9
ADVISORYhttps://github.com/zmartzone/mod_auth_openidc/security/advisories/GHSA-55r8-6w97-xxr4
ADVISORYhttps://lists.debian.org/debian-lts-announce/2023/04/msg00034.html
ADVISORYhttps://security.netapp.com/advisory/ntap-20210902-0001/

All References (12)

→
https://github.com/zmartzone/mod_auth_openidc/commit/dc672688dc1f2db7df8ad4abebc367116017a449Patch · Third Party Advisory
→
https://github.com/zmartzone/mod_auth_openidc/releases/tag/v2.4.9Release Notes · Third Party Advisory
→
https://github.com/zmartzone/mod_auth_openidc/security/advisories/GHSA-55r8-6w97-xxr4Mitigation · Third Party Advisory
→
https://lists.debian.org/debian-lts-announce/2023/04/msg00034.htmlMailing List · Third Party Advisory
→
https://security.netapp.com/advisory/ntap-20210902-0001/Third Party Advisory
→
https://www.oracle.com/security-alerts/cpuapr2022.htmlPatch · Third Party Advisory
→
https://github.com/zmartzone/mod_auth_openidc/commit/dc672688dc1f2db7df8ad4abebc367116017a449Patch · Third Party Advisory
→
https://github.com/zmartzone/mod_auth_openidc/releases/tag/v2.4.9Release Notes · Third Party Advisory
→
https://github.com/zmartzone/mod_auth_openidc/security/advisories/GHSA-55r8-6w97-xxr4Mitigation · Third Party Advisory
→
https://lists.debian.org/debian-lts-announce/2023/04/msg00034.htmlMailing List · Third Party Advisory
→
https://security.netapp.com/advisory/ntap-20210902-0001/Third Party Advisory
→
https://www.oracle.com/security-alerts/cpuapr2022.htmlPatch · Third Party Advisory

Quick Facts

CVE IDCVE-2021-32785
CVSS Score7.5 / 10
SeverityHIGH
WeaknessCWE-134
CISA KEVNo
Affected4 vendor(s)
PublishedJul 22, 2021

Related CVEs (CWE-134)

CVE-2010-2451
10.0
CVE-2006-3573
10.0
CVE-2006-3628
10.0
CVE-2007-5561
10.0
CVE-2008-6520
10.0
CVE-2009-2548
10.0

Recommended Actions

  • →Apply vendor patches immediately
  • →Monitor CVE-2021-32785 in threat intel feeds
  • →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWatch. CVE data is provided under the NVD usage policy.
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