LowCVE-2026-55467

CUPS fax option values bypass the CVE-2026-34980 control-character sanitizer (incomplete fix) (CVE-2026-55467)

Published 15.10.2026Last modified 20.10.2026Sources: Msrc Update Guide, CVE.org, BSI

Public exploit

What is affected, what to do

An exploit is publicly available. Update OpenPrinting CUPS to version 2.4.20.

Affected: OpenPrinting CUPS lt *..2.4.20
Fixed in: OpenPrinting CUPS 2.4.20

Not sure whether and how you are affected? Ask a question about this vulnerability

Metrics

2.5

Priority

XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

Source: Vendor (CNA), CVSS v3

2.5

CVSS v3

Severity Low on the scale from 0 to 10.

Source: Msrc Update Guide, CVE.org, BSI

0.2 %

EPSS score

Low — model estimates < 1% exploitation likelihood.

Source: FIRST EPSS, percentile 7.8

Show all metrics

Severity: Low
Priority (0–325) The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first? Read in glossary: 42.99 Methodology
Exploit maturity An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack. Read in glossary: PoC (publicly reported)
XIEM Effective CVSS XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command. Read in glossary: 2.5 Methodology
CVSS v3 CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions. Read in glossary: 2.5
EPSS score The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“. Read in glossary: 0.2 %; Low — model estimates < 1% exploitation likelihood.
EPSS percentile The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking. Read in glossary: 7.8; Low — this CVE sits in the lower 10% of all CVEs scored today.
KEV status The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching. Read in glossary: —
Published: 15.10.2026
CISA assessment (SSVC): Exploitation: proof of concept · not automatable · Technical impact: partial; Source: CISA Vulnrichment, as of 15 October 2026
CWE CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect. Read in glossary: CWE-93, CWE-94, CWE-150

Detection rules

No NEOSEC detection rule is available for this vulnerability yet.

Classification under NIS2 and CRA

Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

NIS2 NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management. Read in glossary: Handle the vulnerability in regular vulnerability handling under Art. 21(2)(e) NIS2.
CRA The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates. Read in glossary: From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
ISO/IEC 27001 ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security. Read in glossary: Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

Description

OpenPrinting CUPS is an open source printing system for Linux and other Unix-like operating systems. Prior to 2.4.20, the cupsdCreateJob option-string builder in scheduler/job.c maps attacker-controlled destination-uri and pre-dial-string values from a configured fax queue to the phone and faxPrefix options. Unlike ordinary IPP job attributes, these mapped fax values bypass the control-character sanitizer and are copied directly into the filter options argument. A user permitted to submit a job can therefore inject control characters into the downstream option stream. The reporter states that a downstream fax filter passing these values to a shell or modem command could execute code as lp, while the maintainer states that CUPS has no confidentiality or integrity impact because the only known code-executing filter is optional Foomatic and addressed separately, leaving possible disruption of the affected queue. This issue is fixed in version 2.4.20.

Source: Microsoft Security Update Guide, NVD (NIST), cvelistv5, BSI WID Portal, BSI CSAF

Affected products

The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

Affected products
		Affected versions	Fixed in
OpenPrinting	cups	`< 2.4.20`	`2.4.20`
openprinting	cups	`< 2.4.20`	`2.4.20`
Open Source	CUPS	`< 2.4.20`	`2.4.20`

Vendors and products

Weakness classes (CWE)

CWE-93Improper Neutralization of CRLF Sequences ('CRLF Injection')
Base
The product uses CRLF (carriage return line feeds) as a special element, e.g. to separate lines or records, but it does not neutralize or incorrectly neutralizes CRLF sequences from inputs.
Entry at MITRE CWE-93
CWE-94Improper Control of Generation of Code ('Code Injection')
Base
The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.
Entry at MITRE CWE-94
CWE-150Improper Neutralization of Escape, Meta, or Control Sequences
Variant
The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could be interpreted as escape, meta, or control character sequences when they are sent to a downstream component.
Entry at MITRE CWE-150

Public exploit references

Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

Public exploit references

Reference tagged as exploit	github.com (opens in a new tab)	PoC (publicly reported)reported, not verified	—

References & sources

github.comOpenPrinting/cups/security/advisories/GHSA-69qc-prxg-h2c7x_refsource_CONFIRM, Exploit, Vendor advisory
github.comOpenPrinting/cups/commit/0cf4e7814d6810ed3c454222bce3aa342d5416…x_refsource_MISC, Patch
github.comOpenPrinting/cups/commit/a9e7e7a3a019d0fa063d29409d3f82e4c6d5a0…x_refsource_MISC, Patch
github.comOpenPrinting/cups/releases/tag/v2.4.20x_refsource_MISC, Release notes

Changes to this CVE

Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

20.10.2026Initial analysis by NVDNVD

Newly listed as affected:

OpenPrinting CUPS (before 2.4.20)

New references:

Show 6 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
Product configuration	added	—	OR cpe:2.3:a:openprinting:cups::::::::* versions up to (excluding) 2.4.20
Reference type	added	—	GitHub, Inc.: https://github.com/OpenPrinting/cups/commit/0cf4e7814d6810ed3c454222bce3aa342d541681 Types: Patch
Reference type	added	—	GitHub, Inc.: https://github.com/OpenPrinting/cups/commit/a9e7e7a3a019d0fa063d29409d3f82e4c6d5a008 Types: Patch
Reference type	added	—	GitHub, Inc.: https://github.com/OpenPrinting/cups/releases/tag/v2.4.20 Types: Release Notes
Reference type	added	—	CISA-ADP: https://github.com/OpenPrinting/cups/security/advisories/GHSA-69qc-prxg-h2c7 Types: Exploit, Vendor Advisory
Reference type	added	—	GitHub, Inc.: https://github.com/OpenPrinting/cups/security/advisories/GHSA-69qc-prxg-h2c7 Types: Exploit, Vendor Advisory

Source identifier: nvd@nist.gov

15.10.2026ReceivedGitHub

CVSS V3.1: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L

Weakness type: CWE-94, CWE-93, CWE-150

Description added or changed

New references:

Show 10 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
Description	added	—	OpenPrinting CUPS is an open source printing system for Linux and other Unix-like operating systems. Prior to 2.4.20, the cupsdCreateJob option-string builder in scheduler/job.c maps attacker-controlled destination-uri and pre-dial-string values from a configured fax queue to the phone and faxPrefix options. Unlike ordinary IPP job attributes, these mapped fax values bypass the control-character sanitizer and are copied directly into the filter options argument. A user permitted to submit a job can therefore inject control characters into the downstream option stream. The reporter states that a downstream fax filter passing these values to a shell or modem command could execute code as lp, while the maintainer states that CUPS has no confidentiality or integrity impact because the only known code-executing filter is optional Foomatic and addressed separately, leaving possible disruption of the affected queue. This issue is fixed in version 2.4.20.
CVSS	added	—	AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L
Weakness type (CWE)	added	—	CWE-94
Weakness type (CWE)	added	—	CWE-93
Weakness type (CWE)	added	—	CWE-150
Affected versions (publisher)	added	—	New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/55xxx/CVE-2026-55467.json">CVE-2026-55467</a>
Reference	added	—	https://github.com/OpenPrinting/cups/commit/0cf4e7814d6810ed3c454222bce3aa342d541681
Reference	added	—	https://github.com/OpenPrinting/cups/commit/a9e7e7a3a019d0fa063d29409d3f82e4c6d5a008
Reference	added	—	https://github.com/OpenPrinting/cups/releases/tag/v2.4.20
Reference	added	—	https://github.com/OpenPrinting/cups/security/advisories/GHSA-69qc-prxg-h2c7

Source identifier: security-advisories@github.com

15.10.2026Record modifiedCISA ADP

CISA assessment (SSVC): exploitation: proof of concept, automatable: no

New references:

https://github.com/OpenPrinting/cups/security/advisories/GHSA-69qc-prxg-h2c7

Show 2 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
Reference	added	—	https://github.com/OpenPrinting/cups/security/advisories/GHSA-69qc-prxg-h2c7
SSVC assessment	added	—	{"id":"CVE-2026-55467","role":"CISA Coordinator","options":[{"exploitation":"poc"},{"automatable":"no"},{"technicalImpact":"partial"}],"version":"2.0.3","timestamp":"2026-10-15T17:49:04.144102Z"}

Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

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