Medium Access control exploit reference

CVE-2026-27447 — OpenPrinting CUPS: Authorization bypass via case-insensitive group-member lookup

OpenPrinting CUPS is an open source printing system for Linux and other Unix-like operating systems. In versions 2.4.16 and prior, CUPS daemon (cupsd) contains an authorization bypass vulnerability due to case-insensitive username comparison during authorization checks. The vulnerability allows an unprivileged user to gain unauthorized access to restricted operations by using a user with a username that differs only in case from an authorized user. At time of publication, there are no publicly available patches.

Published Apr 3, 2026 · Updated Oct 13, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: GitHub_M

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 0.3% (30-day exploitation probability)+2
Technical severity (medium)+3
CISA SSVC: exploitation "poc"+5

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

0.26%

ahead of 16% of scored CVEs · Oct 14, 2026

Affects

Openprinting

Cups

CVSS base

6.3

Medium · 3 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation

Proof of concept

none · proof-of-concept · active

Automatable

can an attacker script the kill-chain steps

Technical impact

Partial

partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

Documented patch — github.com (NIST National Vulnerability Database)

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Openprinting Cups).
Apply the fixed version or the patch documented under Remediation.
Exploitation requires user interaction: tighten email/web filtering and warn affected users.
Search available logs for exploit probes matching the vulnerability class (access control), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Openprinting	Cups	≤ 2.4.16	Vulnerable	NIST National Vulnerability Database
Openprinting	Cups	version <= 2.4.16	Vulnerable	CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Network

Attack complexity

Low

Privileges required

Low

User interaction

Required

Scope

Unchanged

Confidentiality

High

Integrity

Low

Availability

None

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
6.3	CVSS 3.1	Medium	2.1	4.2	nvd@nist.gov via NIST National Vulnerability Database
4.8	CVSS 3.1	Medium	0.5	4.2	security-advisories@github.com via NIST National Vulnerability Database
4.8	CVSS 3.1	Medium	—	—	GitHub_M via CVE Program (cve.org) e CISA ADP

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:L/A:N (score shown at the top: nvd@nist.gov)

Scoring entities (NIST, CNA, ADP) score independently; each score is shown with its origin. For prioritization we use 6.3 (NVD (NIST)) as a conservative provisional reference — not a definitive official score.

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-863 · Incorrect Authorization

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 0.26%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
Audit administrative actions and access to resources outside each user’s normal pattern.

web/proxy/WAF logsnetwork IDS/IPSauthentication logsapplication logs

Timeline

What happened to this CVE, newest first.

2026
Affected products added · openprinting/cups
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
SSVC assessment updated
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 13, 2026
Fix documented
Oct 13, 2026 · NIST National Vulnerability Database
CVSS changed · 6.3
Oct 13, 2026 · NIST National Vulnerability Database
Source status changed · → Analyzed
Oct 13, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 13, 2026 · NIST National Vulnerability Database
CVE published
Apr 3, 2026 · GitHub_M

Source activity

Repeated readings are counted rather than listed.

1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

2 on the record

github.com/OpenPrinting/cups/security/advisories/GHSA-v987-m8hp-phj9
Exploit, Vendor Advisory, x_refsource_CONFIRM, NIST National Vulnerability Database
github.com/OpenPrinting/cups/commit/88516bf6d9e34cef7a64a704b856b837f70cd220
Patch, x_refsource_MISC, NIST National Vulnerability Database

Elsewhere on this site

Openprinting
every CVE for this vendor

Access control
same class

CWE-863
other pages naming this weakness

Related CVEs (same products)

Medium CVE-2026-61702 OpenPrinting CUPS: root-side banner file disclosure 2h
Low CVE-2026-55453 CUPS ipp backend status-line injection can update queue PPD and lead to conditional RCE as lp via foomatic-rip 2h
Low CVE-2026-55467 CUPS fax option values bypass the CVE-2026-34980 control-character sanitizer (incomplete fix) 2h
Medium CVE-2026-55480 CUPS copy_model() creates a predictable PPD tempfile without O_EXCL/O_NOFOLLOW (symlink TOCTOU, lp → root) 2h
Medium CVE-2026-107888 OpenPrinting CUPS before 2.4.20 contains a NULL pointer dereference in cupsdCheckJobs() when a... 6d
Low CVE-2026-107890 NULL Pointer Dereference in Openprinting Cups 6d

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-27447 is "OpenPrinting CUPS: Authorization bypass via case-insensitive group-member lookup", rated Medium. It affects Cups (Openprinting); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 6.3 describes technical severity. EPSS 0.26% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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