HOMEVULNERABILITIESCVE-2021-32786
MEDIUM

CVE-2021-32786

CWE-601Published: July 22, 2021· Updated: Jun 17, 2026

6.1
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. In versions prior to 2.4.9, `oidc_validate_redirect_url()` does not parse URLs the same way as most browsers do. As a result, this function can be bypassed and leads to an Open Redirect vulnerability in the logout functionality. This bug has been fixed in version 2.4.9 by replacing any backslash of the URL to redirect with slashes to address a particular breaking change between the different specifications (RFC2396 / RFC3986 and WHATWG). As a workaround, this vulnerability can be mitigated by configuring `mod_auth_openidc` to only allow redirection whose destination matches a given regular expression.

NVD Source

Technical Analysis

CVE-2021-32786 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

Exploitation does not require any privileges, though user interaction (Required) is needed, which slightly reduces the risk of mass automated attacks.

The vulnerability has a "Changed" scope, meaning successful exploitation can impact components beyond the vulnerable component itself — such as the host operating system or adjacent services.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorNetwork
Attack ComplexityLow
Privileges Req.None
User InteractionRequired
ScopeChanged
Impact
ConfidentialityLow
IntegrityLow
AvailabilityNone
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Affected Vendors & Products

Apache1 product(s)
http server
Fedora1 product(s)
fedora
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/3a115484eb927bc6daa5737dd84f88ff4bbc5544
PATCHhttps://www.oracle.com/security-alerts/cpuapr2022.html
PATCHhttps://github.com/zmartzone/mod_auth_openidc/commit/3a115484eb927bc6daa5737dd84f88ff4bbc5544
PATCHhttps://www.oracle.com/security-alerts/cpuapr2022.html
ADVISORYhttps://daniel.haxx.se/blog/2017/01/30/one-url-standard-please/
ADVISORYhttps://github.com/zmartzone/mod_auth_openidc/releases/tag/v2.4.9
ADVISORYhttps://github.com/zmartzone/mod_auth_openidc/security/advisories/GHSA-xm4c-5wm5-jqv7
ADVISORYhttps://security.netapp.com/advisory/ntap-20210902-0001/
ADVISORYhttps://daniel.haxx.se/blog/2017/01/30/one-url-standard-please/
ADVISORYhttps://github.com/zmartzone/mod_auth_openidc/releases/tag/v2.4.9
ADVISORYhttps://github.com/zmartzone/mod_auth_openidc/security/advisories/GHSA-xm4c-5wm5-jqv7
ADVISORYhttps://security.netapp.com/advisory/ntap-20210902-0001/

All References (18)

→
https://daniel.haxx.se/blog/2017/01/30/one-url-standard-please/Exploit · Third Party Advisory
→
https://github.com/zmartzone/mod_auth_openidc/commit/3a115484eb927bc6daa5737dd84f88ff4bbc5544Patch · 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-xm4c-5wm5-jqv7Third Party Advisory
→
https://lists.debian.org/debian-lts-announce/2023/04/msg00034.html
→
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FZVF6BSJLRQZ7PFFR4X5JSU6KUJYNOCU/
→
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QXAWKPT5LXZSUTFSJ6IWSZC7RMYYQXQD/
→
https://security.netapp.com/advisory/ntap-20210902-0001/Third Party Advisory
→
https://www.oracle.com/security-alerts/cpuapr2022.htmlPatch · Third Party Advisory
→
https://daniel.haxx.se/blog/2017/01/30/one-url-standard-please/Exploit · Third Party Advisory
→
https://github.com/zmartzone/mod_auth_openidc/commit/3a115484eb927bc6daa5737dd84f88ff4bbc5544Patch · 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-xm4c-5wm5-jqv7Third Party Advisory
→
https://lists.debian.org/debian-lts-announce/2023/04/msg00034.html
→
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FZVF6BSJLRQZ7PFFR4X5JSU6KUJYNOCU/

Quick Facts

CVE IDCVE-2021-32786
CVSS Score6.1 / 10
SeverityMEDIUM
WeaknessCWE-601
CISA KEVNo
Affected3 vendor(s)
PublishedJul 22, 2021

Related CVEs (CWE-601)

CVE-2025-55031
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CVE-2022-31657
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CVE-2024-22891
9.8
CVE-2026-61451
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CVE-2022-40083
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CVE-2026-6795
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Recommended Actions

  • →Apply vendor patches immediately
  • →Monitor CVE-2021-32786 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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