CVE-2019-3877

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.

Published: 2019-03-27 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2019-3877 is rated Moderate Risk (52.3/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 2.13%). EPSS rose +1.32% over the last day, indicating growing attacker interest. Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2019-3877

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.81% 2.13% +1.32%
2 2026-01-16 0.61% 0.81% +0.20%
3 2025-11-21 — 0.61% —

Full EPSS history (18 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2019-3877

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.8 3.0 MEDIUM
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 1.4 [email protected]
6.1 3.0 MEDIUM
CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 2.8 2.7 [email protected]
4.3 2.0 MEDIUM
AV:N/AC:M/Au:N/C:N/I:P/A:N Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:N)
No availability impact.
 8.6 2.9 [email protected]

Weakness enumeration for CVE-2019-3877

OS Trackers for CVE-2019-3877

vendor priority summary link
debian not yet assigned CVE-2019-3877 not yet assigned priority: Debian including 1 source packages (libapache2-mod-auth-mellon), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2019-3877
redhat medium — https://access.redhat.com/security/cve/CVE-2019-3877
ubuntu medium CVE-2019-3877 medium priority: Ubuntu including 1 source packages (libapache2-mod-auth-mellon), 9 status rows across 9 suites (bionic, cosmic, disco, eoan, focal, groovy, trusty, upstream, xenial): released 8, DNE 1. https://ubuntu.com/security/CVE-2019-3877

Affected software / configurations for CVE-2019-3877

Vendor Product Version Raw CPE
mod_auth_mellon_project mod_auth_mellon < 0.14.2 cpe:2.3:a:mod_auth_mellon_project:mod_auth_mellon:*:*:*:*:*:apache:*:*
fedoraproject fedora 29 cpe:2.3:o:fedoraproject:fedora:29:*:*:*:*:*:*:*
redhat enterprise_linux 7.0 cpe:2.3:o:redhat:enterprise_linux:7.0:*:*:*:*:*:*:*
canonical ubuntu_linux 18.04 cpe:2.3:o:canonical:ubuntu_linux:18.04:*:*:*:lts:*:*:*
canonical ubuntu_linux 18.10 cpe:2.3:o:canonical:ubuntu_linux:18.10:*:*:*:*:*:*:*

References for CVE-2019-3877

cvelogic Threat Intelligence