Security readout for executives and security teams
Plain-English summary
This issue lets an attacker abuse certain logout redirects in Apache deployments using mod_auth_openidc before 2.4.9. It is not a server takeover, but it can send users from a trusted site to an attacker-controlled destination, supporting phishing or trust abuse.
Executive priority
Treat this as a moderate-priority fix, highest for internet-facing SSO or customer portals. It does not appear to enable direct compromise, but trusted-domain redirects are useful in phishing and can damage user trust.
Technical view
oidc_validate_redirect_url() parsed redirect URLs differently from common browsers. Backslash handling could bypass validation in logout functionality, causing CWE-601 open redirect. Version 2.4.9 fixes this by replacing backslashes with slashes before validation; a regex-based redirect allowlist is the documented workaround.
Likely exposure
Exposure is limited to Apache 2.x HTTP Server environments running zmartzone mod_auth_openidc before 2.4.9, including deployments receiving it through distribution or vendor packages. The vulnerable surface is logout redirection behavior, not the whole authentication flow.
Exploitation context
The CVE is not listed in KEV, and the provided sources do not state active exploitation. CVSS indicates network access, low attack complexity, no privileges, and required user interaction, with limited integrity impact.
Researcher notes
Primary evidence comes from the GitHub advisory, release, and fixing commit. The root cause is URL parsing inconsistency across RFC2396, RFC3986, and WHATWG behavior. Sources support the affected range, fix version, workaround, and downstream advisories, but not active exploitation.
Mitigation direction
- Upgrade mod_auth_openidc to version 2.4.9 or later.
- Apply relevant vendor package updates where mod_auth_openidc is bundled.
- Configure redirect destinations to match a strict regular expression allowlist.
- Review logout redirect settings for broad or permissive destination patterns.
- Check vendor advisories for embedded or downstream package status.
Validation and detection
- Inventory Apache servers using mod_auth_openidc.
- Confirm installed mod_auth_openidc versions are 2.4.9 or later.
- Review logout redirect configuration for strict destination allowlisting.
- Verify vendor-managed systems have received corresponding security updates.
- Document any exception where upgrade depends on vendor guidance.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-601: User-session and phishing behavior lookup
Client-side and session-facing weaknesses should be reviewed alongside initial-access and user-execution behaviors. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2021-32786 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 4.7 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N2.81.4Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
4.7MediumVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/zmartzone/mod_auth_openidc/releases/tag/v2.4.9CVE reference
- https://github.com/zmartzone/mod_auth_openidc/security/advisories/GHSA-xm4c-5wm5-jqv7CVE reference
- https://github.com/zmartzone/mod_auth_openidc/commit/3a115484eb927bc6daa5737dd84f88ff4bbc5544CVE reference
- https://daniel.haxx.se/blog/2017/01/30/one-url-standard-please/CVE reference
- FEDORA-2021-e3017c538aCVE reference · vendor-advisory
- FEDORA-2021-17f5cedf66CVE reference · vendor-advisory
- https://www.oracle.com/security-alerts/cpuapr2022.htmlCVE reference
- https://security.netapp.com/advisory/ntap-20210902-0001/CVE reference
- [debian-lts-announce] 20230430 [SECURITY] [DLA 3409-1] libapache2-mod-auth-openidc security updateCVE reference · mailing-list
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
URL Redirection to Untrusted Site ('Open Redirect')
URL Redirection to Untrusted Site ('Open Redirect') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.