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Fencer Vulns
medium 6.5

CVE-2026-34978 json

OpenPrinting CUPS: Path traversal in RSS notify-recipient-uri enables file write outside CacheDir/rss (and clobbering of job.cache)

published 2026-04-03 7 mo ago modified 2026-07-20 3 mo ago also EUVD-2026-18884

cvss
6.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 36%
public exploits
0
none known

Summary

OpenPrinting CUPS is an open source printing system for Linux and other Unix-like operating systems. In versions 2.4.16 and prior, the RSS notifier allows .. path traversal in notify-recipient-uri (e.g., rss:///../job.cache), letting a remote IPP client write RSS XML bytes outside CacheDir/rss (anywhere that is lp-writable). In particular, because CacheDir is group-writable by default (typically root:lp and mode 0770), the notifier (running as lp) can replace root-managed state files via temp-file + rename(). This PoC clobbers CacheDir/job.cache with RSS XML, and after restarting cupsd the scheduler fails to parse the job cache and previously queued jobs disappear. At time of publication, there are no publicly available patches.

Patch / fix

  • cups Debian 14 2.4.17-1

debian advisories DEBIAN-CVE-2026-34978

  • cups Ubuntu 22.04 LTS 2.4.1op1-1ubuntu4.20
  • cups Ubuntu 24.04 LTS 2.4.7-1.2ubuntu7.13
  • cups Ubuntu 25.10 2.4.12-0ubuntu3.9
  • cups Ubuntu 26.04 LTS 2.4.16-1ubuntu1.2

ubuntu advisories UBUNTU-CVE-2026-34978

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • cups hummingbird 1 2.4.17-1.hum1
  • cups-lpd hummingbird 1 2.4.17-1.hum1
  • cups-libs hummingbird 1 2.4.17-1.hum1
  • cups-client hummingbird 1 2.4.17-1.hum1
  • cups-ipptool hummingbird 1 2.4.17-1.hum1
  • cups-filesystem hummingbird 1 2.4.17-1.hum1
  • cups-printerapp hummingbird 1 2.4.17-1.hum1

red hat advisories RHSA-2026:8814

  • cups SLE Module for Development Tools 15 SP7, SLE Module for Desktop Applications 15 SP7, SLE Module for Basesystem 15 SP7 +4 more 2.2.7-150000.3.93.1
  • cups SLES LTSS Extended Security 12 SP5 1.7.5-20.67.1

suse advisories SUSE-SU-2026:2732-1SUSE-SU-2026:2718-1

  • cups openSUSE Tumbleweed 2.4.17-1.1

opensuse advisories openSUSE-SU-2026:10589-1

  • cups Alpine 3.24, Alpine 3.23, Alpine 3.22 +2 more 2.4.18-r0

alpine advisories ALPINE-CVE-2026-34978

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • cups Azure Linux 3.0 2.4.17-1

azure linux advisories AZL-81819

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

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-2026-34978 updated cvss 6.5

cups: OpenPrinting CUPS: Denial of Service via path traversal in RSS notifier

  • Red Hat Enterprise Linux 6 cups, cups-lpd, cups-php, cups-libs Red Hat Enterprise Linux 7 cups, cups-lpd, cups-libs, cups-client, cups-ipptool, cups-filesystem
    affected: workaround, no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 8 cups, cups-lpd, cups-libs, cups-client, cups-ipptool, cups-filesystem Red Hat Enterprise Linux 9 cups, cups-lpd, cups-libs, cups-client, cups-ipptool, cups-filesystem, +1 more Red Hat Enterprise Linux 10 cups Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-8
    affected: workaround, no fix available “Fix deferred”
  • Red Hat Hardened Images cups 2.4.17-1.hum1, cups-lpd 2.4.17-1.hum1, cups-libs 2.4.17-1.hum1, cups-client 2.4.17-1.hum1, cups-ipptool 2.4.17-1.hum1, cups-filesystem 2.4.17-1.hum1, +1 more
    fixed: vendor fix RHSA-2026:8814

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

CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
partial
Assessed
7 mo ago

Exploit prediction

0.42% chance of exploitation in the next 30 days, higher than 36% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/OpenPrinting/cups/security/advisories/GHSA-f53q-7mxp-9gcr referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L

Affected products

  • OpenPrinting cups

Classification

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

References

Sources

Fencer Vulns 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.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.