CVE-2019-3878: A vulnerability was found in mod_auth_mellon before v0.14.2

Q: How do I fix CVE-2019-3878?

mod auth mellon: upgrade to 0.14.2; fedora: mitigate or apply the listed mitigation; enterprise linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Q: Is CVE-2019-3878 being exploited?

CVE-2019-3878 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2019-3878 affect?

CVE-2019-3878 affects mod auth mellon, fedora, enterprise linux. Severity is high (CVSS 8.1). A vulnerability was found in mod_auth_mellon before v0.14.2. If Apache is configured as a reverse proxy and mod_auth_mellon is configured to only let through authenticated users (with the require valid-user directive), adding special HTTP h

Q: How urgent is CVE-2019-3878?

Priority 60/100. High severity; Public exploit reference; On your watchlist

This week

HIGH 8.1WATCHLISTUPGRADEMITIGATEMITIGATE

CVE-2019-3878 is a high-severity flaw (CVSS 8.1) affecting mod auth mellon, fedora, enterprise linux. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A vulnerability was found in mod_auth_mellon before v0.14.2. If Apache is configured as a reverse proxy and mod_auth_mellon is configured to only let through authenticated users (with the require valid-user directive), adding special HTTP headers that are normally used to start the special SAML ECP (non-browser based) can be used to bypass authentication.

Why this priority

High severity
Public exploit reference
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	8.1 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	3.0% (top 13%)
CISA exploited list	No
Weakness	CWE-305, CWE-287
Published	2019-03-26
Last modified	2026-06-17

Publisher (CNA): Red Hat, Inc. · Vendor: fedoraproject · mod auth mellon project · redhat

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2019-03-26 18:29 UTCPublished CVE record published
2026-06-17 02:35 UTCUpdated Record last modified

mod auth mellon project mod auth mellon UPGRADE

Affected: < 0.14.2

Fixed in: 0.14.2

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy mod-auth-mellon || rpm -q mod-auth-mellon || mod-auth-mellon --version

2. UPGRADE to 0.14.2 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade mod-auth-mellon

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade mod-auth-mellon

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

fedoraproject fedora MITIGATE

Affected: 29 · 30

Fixed in: no fixed release known

Safe to downgrade to: a release before 29

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

redhat enterprise linux MITIGATE

Affected: 7.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 7.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

redhat enterprise linux desktop MITIGATE

Affected: 7.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 7.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

redhat enterprise linux server MITIGATE

Affected: 7.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 7.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

redhat enterprise linux server aus MITIGATE

Affected: 7.6

Fixed in: no fixed release known

Safe to downgrade to: a release before 7.6

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2019-3878?

mod auth mellon: upgrade to 0.14.2; fedora: mitigate or apply the listed mitigation; enterprise linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2019-3878 being exploited?

CVE-2019-3878 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2019-3878 affect?

CVE-2019-3878 affects mod auth mellon, fedora, enterprise linux. Severity is high (CVSS 8.1). A vulnerability was found in mod_auth_mellon before v0.14.2. If Apache is configured as a reverse proxy and mod_auth_mellon is configured to only let through authenticated users (with the require valid-user directive), adding special HTTP h

How urgent is CVE-2019-3878?

Priority 60/100. High severity; Public exploit reference; On your watchlist

Related CVEs

CVE-2021-3639 MEDIUM 6.1 UPGRADE A flaw was found in mod_auth_mellon where it does not sanitize logout URLs properly
CVE-2019-3877 MEDIUM 5.8 UPGRADE MITIGATE A vulnerability was found in mod_auth_mellon before v0.14.2
CVE-2019-13038 MEDIUM 6.1 UPGRADE DOWNGRADE mod_auth_mellon through 0.14.2 has an Open Redirect via the login?ReturnTo= substring, as demonstrated by omit

References

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