CVE-2021-3639
A flaw was found in mod_auth_mellon where it does not sanitize logout URLs properly. This issue...
A flaw was found in mod_auth_mellon where it does not sanitize logout URLs properly. This issue could be used by an attacker to facilitate phishing attacks by tricking users into visiting a trusted web application URL that redirects to an external and potentially malicious server. The highest threat from this liability is to confidentiality and integrity.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- Required
What an attacker can affect
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
Exploit likelihood
What each source reports
NVD Score used
6.1
A flaw was found in mod_auth_mellon where it does not sanitize logout URLs properly. This issue could be used by an attacker to facilitate phishing attacks by tricking users into visiting a trusted web application URL that redirects to an external and potentially malicious server. The highest threat from this liability is to confidentiality and integrity.
- Record
CVE-2021-3639- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - Weakness
- CWE-601
- Updated
- 2026-11-02
CVE List No score
A flaw was found in mod_auth_mellon where it does not sanitize logout URLs properly. This issue could be used by an attacker to facilitate phishing attacks by tricking users into visiting a trusted web application URL that redirects to an external and potentially malicious server. The highest threat from this liability is to confidentiality and integrity.
- Record
CVE-2021-3639- Weakness
- CWE-601
- Updated
- 2026-11-02
EUVDEUVD-2021-26939 No score
A flaw was found in mod_auth_mellon where it does not sanitize logout URLs properly. This issue could be used by an attacker to facilitate phishing attacks by tricking users into visiting a trusted web application URL that redirects to an external and potentially malicious server. The highest threat from this liability is to confidentiality and integrity.
- Record
EUVD-2021-26939- Updated
- 2026-11-03
GitHub AdvisoriesGHSA-mhcv-7w89-jjj5
6.1
A flaw was found in mod_auth_mellon where it does not sanitize logout URLs properly. This issue...
A flaw was found in mod_auth_mellon where it does not sanitize logout URLs properly. This issue could be used by an attacker to facilitate phishing attacks by tricking users into visiting a trusted web application URL that redirects to an external and potentially malicious server. The highest threat from this liability is to confidentiality and integrity.
- Record
GHSA-mhcv-7w89-jjj5- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - Weakness
- CWE-601
- Updated
- 2026-11-02
OSVAZL-10651
6.1
CVE-2021-3639 affecting package mod_auth_mellon for versions less than 0.16.0-4
A flaw was found in mod_auth_mellon where it does not sanitize logout URLs properly. This issue could be used by an attacker to facilitate phishing attacks by tricking users into visiting a trusted web application URL that redirects to an external and potentially malicious server. The highest threat from this liability is to confidentiality and integrity.
- Record
AZL-10651- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - Updated
- 2026-11-02
OSVAZL-36962
6.1
CVE-2021-3639 affecting package mod_auth_mellon for versions less than 0.16.0-4
A flaw was found in mod_auth_mellon where it does not sanitize logout URLs properly. This issue could be used by an attacker to facilitate phishing attacks by tricking users into visiting a trusted web application URL that redirects to an external and potentially malicious server. The highest threat from this liability is to confidentiality and integrity.
- Record
AZL-36962- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - Updated
- 2026-11-05
Show 10 moreShow less
OSV
6.1
A flaw was found in mod_auth_mellon where it does not sanitize logout URLs properly. This issue could be used by an attacker to facilitate phishing attacks by tricking users into visiting a trusted web application URL that redirects to an external and potentially malicious server. The highest threat from this liability is to confidentiality and integrity.
- Record
CVE-2021-3639- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - Updated
- 2026-11-02
OSVDEBIAN-CVE-2021-3639
6.1
A flaw was found in mod_auth_mellon where it does not sanitize logout URLs properly. This issue could be used by an attacker to facilitate phishing attacks by tricking users into visiting a trusted web application URL that redirects to an external and potentially malicious server. The highest threat from this liability is to confidentiality and integrity.
- Record
DEBIAN-CVE-2021-3639- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - Updated
- 2026-11-02
OSVRHSA-2022:1934
6.1
Red Hat Security Advisory: mod_auth_mellon security update
- Record
RHSA-2022:1934- CVSS 3.0
- 6.1 Medium
CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - Updated
- 2026-11-02
OSVRLSA-2022:1934
6.1
Moderate: mod_auth_mellon security update
The mod_auth_mellon module for the Apache HTTP Server is an authentication service that implements the SAML 2.0 federation protocol. The module grants access based on the attributes received in assertions generated by an IdP server.
Security Fix(es):
- mod_auth_mellon: Open Redirect vulnerability in logout URLs (CVE-2021-3639)
For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.
Additional Changes:
For detailed information on changes in this release, see the Rocky Linux 8.6 Release Notes linked from the References section.
- Record
RLSA-2022:1934- CVSS 3.0
- 6.1 Medium
CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - Updated
- 2026-11-02
OSVUBUNTU-CVE-2021-3639
6.1
A flaw was found in mod_auth_mellon where it does not sanitize logout URLs properly. This issue could be used by an attacker to facilitate phishing attacks by tricking users into visiting a trusted web application URL that redirects to an external and potentially malicious server. The highest threat from this liability is to confidentiality and integrity.
- Record
UBUNTU-CVE-2021-3639- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - Updated
- 2026-11-02
OSVALSA-2022:1934 No score
Moderate: mod_auth_mellon security update
The mod_auth_mellon module for the Apache HTTP Server is an authentication service that implements the SAML 2.0 federation protocol. The module grants access based on the attributes received in assertions generated by an IdP server.
Security Fix(es):
- mod_auth_mellon: Open Redirect vulnerability in logout URLs (CVE-2021-3639)
For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.
Additional Changes:
For detailed information on changes in this release, see the AlmaLinux Release Notes linked from the References section.
- Record
ALSA-2022:1934- Updated
- 2026-11-02
OSVopenSUSE-SU-2024:13848-1 No score
apache2-mod_auth_mellon-0.19.0-1.1 on GA media
These are all security issues fixed in the apache2-mod_auth_mellon-0.19.0-1.1 package on the GA media of openSUSE Tumbleweed.
- Record
openSUSE-SU-2024:13848-1- Updated
- 2026-11-02
OSVSUSE-SU-2021:2912-1 No score
Security update for apache2-mod_auth_mellon
This update for apache2-mod_auth_mellon fixes the following issues:
- CVE-2021-3639: Fixed Open Redirect vulnerability in logout URLs (bsc#1188926).
- Record
SUSE-SU-2021:2912-1- Updated
- 2026-11-02
OSVSUSE-SU-2022:1524-1 No score
Security update for apache2-mod_auth_mellon
This update for apache2-mod_auth_mellon fixes the following issues:
- CVE-2021-3639: Fixed open Redirect vulnerability in logout URLs (bsc#1188926)
- Record
SUSE-SU-2022:1524-1- Updated
- 2026-11-02
OSVUSN-5069-1 No score
libapache2-mod-auth-mellon vulnerability
It was discovered that mod-auth-mellon incorrectly filtered certain URLs. A remote attacker could possibly use this issue to perform an open redirect attack.
- Record
USN-5069-1- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
mod_auth_mellonAlmaLinux:8 |
before 0.14.0-12.el8.1 | 0.14.0-12.el8.1 |
mod_auth_mellon-diagnosticsAlmaLinux:8 |
before 0.14.0-12.el8.1 | 0.14.0-12.el8.1 |
mod_auth_mellonAzure Linux:2 |
before 0.16.0-4 | 0.16.0-4 |
mod_auth_mellonAzure Linux:3 |
before 0.16.0-4 | 0.16.0-4 |
libapache2-mod-auth-mellonDebian:12 |
before 0.18.0-1 | 0.18.0-1 |
libapache2-mod-auth-mellonDebian:13 |
before 0.18.0-1 | 0.18.0-1 |
libapache2-mod-auth-mellonDebian:14 |
before 0.18.0-1 | 0.18.0-1 |
libapache2-mod-auth-mellonDebian:10 From an advisory covering 2 CVEs |
before 0.14.2-1+deb10u1, plus listed versions 0.14.2-1 |
0.14.2-1+deb10u1 |
mod_auth_mellonRed Hat:enterprise_linux:8::appstream |
before 0:0.14.0-12.el8.1 | 0:0.14.0-12.el8.1 |
mod_auth_mellon-debuginfoRed Hat:enterprise_linux:8::appstream |
before 0:0.14.0-12.el8.1 | 0:0.14.0-12.el8.1 |
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| Package | Affected | Fixed |
|---|---|---|
mod_auth_mellon-debugsourceRed Hat:enterprise_linux:8::appstream |
before 0:0.14.0-12.el8.1 | 0:0.14.0-12.el8.1 |
mod_auth_mellon-diagnosticsRed Hat:enterprise_linux:8::appstream |
before 0:0.14.0-12.el8.1 | 0:0.14.0-12.el8.1 |
mod_auth_mellon-diagnostics-debuginfoRed Hat:enterprise_linux:8::appstream |
before 0:0.14.0-12.el8.1 | 0:0.14.0-12.el8.1 |
mod_auth_mellonRocky Linux:8 |
before 0:0.14.0-12.el8.1 | 0:0.14.0-12.el8.1 |
apache2-mod_auth_mellonSUSE:Linux Enterprise Server 12 SP5 |
before 0.16.0-8.6.1 | 0.16.0-8.6.1 |
apache2-mod_auth_mellonSUSE:Linux Enterprise Server for SAP Applications 12 SP5 |
before 0.16.0-8.6.1 | 0.16.0-8.6.1 |
apache2-mod_auth_mellonSUSE:Linux Enterprise Module for Server Applications 15 SP3 |
before 0.17.0-150200.5.7.1 | 0.17.0-150200.5.7.1 |
apache2-mod_auth_mellonSUSE:Linux Enterprise High Performance Computing 15 SP2-ESPOS |
before 0.17.0-150200.5.7.1 | 0.17.0-150200.5.7.1 |
apache2-mod_auth_mellonSUSE:Linux Enterprise High Performance Computing 15 SP2-LTSS |
before 0.17.0-150200.5.7.1 | 0.17.0-150200.5.7.1 |
apache2-mod_auth_mellonSUSE:Linux Enterprise Real Time 15 SP2 |
before 0.17.0-150200.5.7.1 | 0.17.0-150200.5.7.1 |
apache2-mod_auth_mellonSUSE:Linux Enterprise Server 15 SP2-BCL |
before 0.17.0-150200.5.7.1 | 0.17.0-150200.5.7.1 |
apache2-mod_auth_mellonSUSE:Linux Enterprise Server 15 SP2-LTSS |
before 0.17.0-150200.5.7.1 | 0.17.0-150200.5.7.1 |
apache2-mod_auth_mellonSUSE:Linux Enterprise Server for SAP Applications 15 SP2 |
before 0.17.0-150200.5.7.1 | 0.17.0-150200.5.7.1 |
apache2-mod_auth_mellonSUSE:Manager Proxy 4.1 |
before 0.17.0-150200.5.7.1 | 0.17.0-150200.5.7.1 |
apache2-mod_auth_mellonSUSE:Manager Retail Branch Server 4.1 |
before 0.17.0-150200.5.7.1 | 0.17.0-150200.5.7.1 |
apache2-mod_auth_mellonSUSE:Manager Server 4.1 |
before 0.17.0-150200.5.7.1 | 0.17.0-150200.5.7.1 |
apache2-mod_auth_mellonSUSE:Enterprise Storage 7 |
before 0.17.0-150200.5.7.1 | 0.17.0-150200.5.7.1 |
apache2-mod_auth_mellonopenSUSE:Leap 15.3 |
before 0.17.0-150200.5.7.1 | 0.17.0-150200.5.7.1 |
apache2-mod_auth_mellonopenSUSE:Leap 15.4 |
before 0.17.0-150200.5.7.1 | 0.17.0-150200.5.7.1 |
libapache2-mod-auth-mellonUbuntu:16.04:LTS |
All versions, plus listed versions 0.10.0-10.11.0-10.12.0-10.12.0-2+deb9u1build0.16.04.1 |
None known |
libapache2-mod-auth-mellonUbuntu:18.04:LTS |
before 0.13.1-1ubuntu0.3, plus listed versions 0.13.1-10.13.1-1build10.13.1-1build20.13.1-1ubuntu0.10.13.1-1ubuntu0.2 |
0.13.1-1ubuntu0.3 |
libapache2-mod-auth-mellonUbuntu:20.04:LTS |
before 0.16.0-1ubuntu0.1, plus listed versions 0.14.2-1ubuntu10.14.2-1ubuntu20.16.0-1 |
0.16.0-1ubuntu0.1 |
libapache2-mod-auth-mellonUbuntu:22.04:LTS |
before 0.17.0-1ubuntu1 | 0.17.0-1ubuntu1 |
apache2-mod_auth_mellonopenSUSE:Tumbleweed |
before 0.19.0-1.1 | 0.19.0-1.1 |
History
| Recorded | Changed | Sources |
|---|---|---|
| affected | ||
| facts | OSV | |
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-3639 is a medium vulnerability (CVSS 6.1) in Uninett Mod Auth Mellon, published August 4, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.03%, the 63rd percentile. Fixed in mod_auth_mellon 0.14.0-12.el8.1.
References
bugzilla.redhat.com/show_bug.cgi?id=1980648
access.redhat.com/security/cve/CVE-2021-3639
github.com/latchset/mod_auth_mellon/commit/42a11261b9dad2e48d70bdff7c53dd57a12db6f5
nvd.nist.gov/vuln/detail/CVE-2021-3639
access.redhat.com/errata/RHSA-2022:1934
github.com/advisories/GHSA-mhcv-7w89-jjj5
Show 15 moreShow less
errata.almalinux.org/8/ALSA-2022-1934.html
vulners.com/cve/CVE-2021-3639
security-tracker.debian.org/tracker/CVE-2021-3639
access.redhat.com/security/updates/classification
access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/html/8.6_release_notes
security.access.redhat.com/data/csaf/v2/advisories/2022/rhsa-2022_1934.json
cve.org/CVERecord?id=CVE-2021-3639
errata.rockylinux.org/RLSA-2022:1934
suse.com/support/update/announcement/2021/suse-su-20212912-1
bugzilla.suse.com/1188926
suse.com/security/cve/CVE-2021-3639
suse.com/support/update/announcement/2022/suse-su-20221524-1
ubuntu.com/security/CVE-2021-3639
ubuntu.com/security/notices/USN-5069-1
ubuntu.com/security/notices/USN-5069-2