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Fencer Intel
medium 6.3

CVE-2026-104721 json

Logback: Incomplete protection against CVE-2026-19880

published last mo. modified last mo. also EUVD-2026-91633

cvss
6.3
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 26%
public exploits
0
none known

Summary

Path-traversal vulnerability in QOS.CH Sarl Logback-classic on Java (logback-classic module) allows path-traversal vulnerability. More specifically, an MDC-based discriminator value flows unsanitized into a nested FileAppender path, letting an attacker who influences that MDC value (e.g. via an HTTP header) create and append log files outside the intended directory.

This issue affects Logback-classic: from 0.9.14 through 1.6.4.  This vulnerability is similar to CVE-2026-19880 but involves other attack techniques.

Patch / fix

  • QOS.CH Sarl Logback-classic 1.6.5
  • logback openSUSE Tumbleweed 1.6.5-2.1

opensuse advisories openSUSE-SU-2026:11985-1

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-104721 updated cvss 5.6

ch.qos.logback/logback-classic: logback-classic: Arbitrary file write via path traversal in MDC discriminator

  • Red Hat Migration Toolkit for Applications 8 mta/mta-cli-rhel9, mta/mta-java-external-provider-rhel9 Red Hat OpenShift Serverless openshift-serverless-1/kn-ekb-receiver-rhel9, openshift-serverless-1/kn-ekb-dispatcher-rhel9 Red Hat build of Apache Camel - HawtIO 4 logback-classic 1.5.32 Red Hat Ceph Storage 9 libarrow, parquet-libs Red Hat Enterprise Linux 7 groovy, groovy-javadoc Red Hat Enterprise Linux 8 sisu, guava, jansi, jsoup, maven, slf4j, +60 more
    +5 more products
    Red Hat Enterprise Linux 9 sisu, guava, jansi, maven, slf4j, jsr-305, +31 more Red Hat Enterprise Linux 10 sisu 0.3.5-15.el10, easymock 4.3-9.el10, apache-commons-logging 1.3.4-1.el10 Red Hat JBoss Web Server 7 jws7-jboss-logging 3.6.2-1.Final_redhat_00001.1.el8jws Red Hat OpenShift Dev Spaces devspaces/server-rhel9, devspaces/openvsx-rhel9, devspaces/pluginregistry-rhel9 Red Hat Satellite 6 candlepin, puppetserver, candlepin-selinux, openvox-server 8.15.2-1.el9sat
    affected: workaround, no fix available “Fix deferred”
  • Red Hat Hardened Images maven3.9 3.9.16-0.3.hum1
    not affected: component not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.33% chance of exploitation in the next 30 days, higher than 26% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 4.0 6.3 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/S:P/AU:N/RE:M/U:Green
CNA 4.0 6.3 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:P/AU:N/R:X/V:X/RE:M/U:Green

Affected products

  • QOS.CH Sarl Logback-classic

Classification

Weakness
  • CWE-22 Improper Limitation of a Pathname to a Restricted Directory

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.