CVE-2019-3877: A vulnerability was found in mod_auth_mellon before v0.14.2

Q: How do I fix CVE-2019-3877?

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-2019-3877 being exploited?

CVE-2019-3877 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-2019-3877 affect?

CVE-2019-3877 affects mod auth mellon, fedora, enterprise linux. Severity is medium (CVSS 5.8). A vulnerability was found in mod_auth_mellon before v0.14.2. An open redirect in the logout URL allows requests with backslashes to pass through by assuming that it is a relative URL, while the browsers silently convert backslash characters

Q: How urgent is CVE-2019-3877?

Priority 51/100. Remotely exploitable, no login, no user action; On your watchlist

This month

MEDIUM 5.8REMOTEWATCHLISTUPGRADEMITIGATEMITIGATE

CVE-2019-3877 is a medium-severity flaw (CVSS 5.8) 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. An open redirect in the logout URL allows requests with backslashes to pass through by assuming that it is a relative URL, while the browsers silently convert backslash characters into forward slashes treating them as an absolute URL. This mismatch allows an attacker to bypass the redirect URL validation logic in apr_uri_parse function.

Why this priority

Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	5.8 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	2.1% (top 18%)
CISA exploited list	No
Weakness	CWE-601
Published	2019-03-27
Last modified	2026-06-17

Publisher (CNA): Red Hat, Inc. · Vendor: canonical · 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

2019-03-27 13:29 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

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.

canonical ubuntu linux MITIGATE

Affected: 18.04 · 18.10

Fixed in: no fixed release known

Safe to downgrade to: a release before 18.04

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-2019-3877?

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-2019-3877 being exploited?

CVE-2019-3877 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-2019-3877 affect?

CVE-2019-3877 affects mod auth mellon, fedora, enterprise linux. Severity is medium (CVSS 5.8). A vulnerability was found in mod_auth_mellon before v0.14.2. An open redirect in the logout URL allows requests with backslashes to pass through by assuming that it is a relative URL, while the browsers silently convert backslash characters

How urgent is CVE-2019-3877?

Priority 51/100. Remotely exploitable, no login, no user action; On your watchlist

Software pages

Ubuntu vulnerabilities

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-2019-3878 HIGH 8.1 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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