Two case-insensitive comparisons on request-derived usernames outside the main authorization path in CUPS's scheduler (printer ACL validation and private-attribute filtering) could allow bypass of username-based access controls in certain configurations.

It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2023-2026-3415 advisory.

    An argument injection flaw was found in CUPS. When email notification is configured, the CUPS scheduler     accepts printer subscription requests that supply a mailto notify-recipient-uri. The mailto notifier     passes the recipient address to the configured sendmail program without ensuring it cannot be interpreted     as command-line options. A remote attacker who can reach the CUPS service could supply a crafted recipient     value starting with - to influence sendmail behavior. Successful exploitation depends on the installed     mail transfer agent and CUPS network exposure, and may lead to execution of attacker-controlled commands     with the privileges of the CUPS service user. (CVE-2026-105326)

    A flaw was found in CUPS. When processing embedded job ticket comments within documents, the service     improperly handles specific IPP attributes, causing an unhandled null pointer dereference. An     unauthenticated attacker permitted to submit jobs to a shared printer queue can send a crafted Internet     Printing Protocol (IPP) request to crash the print daemon, resulting in a temporary Denial of Service     (DoS) for all printing services. (CVE-2026-107655)

    OpenPrinting CUPS through 2.4.20 contains a resource-exhaustion vulnerability in the submission-timeout     handling of cupsdCheckJobs(). The scheduler suppresses timeout processing for all pending jobs whenever     any client connection has an in-flight Send-Document operation, without matching that connection to the     job being examined. A client allowed to reach the IPP service can hold an incomplete HTTP request     containing parsed Send-Document headers before operation authorization, preventing unrelated incomplete     jobs from expiring. Where Create-Job submission is allowed, incomplete jobs can accumulate until MaxJobs     is exhausted and further legitimate print submissions are rejected. The suppression ends when the held     connection closes. (CVE-2026-107885)

    OpenPrinting CUPS before 2.4.20 contains a double-free in printer-class management. When CUPS-Add-Modify-     Class replaces an existing class member list, add_class() frees pclass->printers without clearing the     pointer. If subsequent validation fails, the class retains the dangling pointer; CUPS-Delete-Class     subsequently frees the same allocation in cupsdDeletePrinter(). A client authorized to modify and delete     classes can cause scheduler-wide denial of service. The default policy requires @SYSTEM privileges.
    (CVE-2026-107886)

    OpenPrinting CUPS before 2.4.20 contains a NULL pointer dereference in cupsdCheckJobs() when a job marked     job-held-on-create refers to a temporary printer that has been automatically deleted. Temporary-printer     cleanup can remove the destination without canceling its held jobs, and the scheduler dereferences the     NULL result of cupsdFindDest() while checking holding_new_jobs. This terminates cupsd and interrupts all     queues managed by that process. In some plausible scenarios, an unprivileged submission can trigger this.
    (CVE-2026-107888)

    OpenPrinting CUPS before 2.4.20 contains a NULL pointer dereference caused by repeated IPP group tags in     job-creation requests. IPP parsing creates unnamed separator attributes with IPP_TAG_ZERO, but add_job()     converts these separators to IPP_TAG_JOB. During job startup, get_options()/ipp_length() subsequently     calls strlen() on a NULL attribute name, terminating cupsd and disrupting all queues. A single crafted     Print-Job request can trigger the crash when the client can reach the scheduler and submit jobs to an     accepting, enabled queue supporting the submitted document format. Anonymous submission is possible when     permitted by listener and access-control configuration. (CVE-2026-107890)

    A malicious or attacker-controlled IPP printer can return a crafted text printer-status attribute, such as     marker-message, containing embedded newline characters. The CUPS ipp backend reports this remote printer     attribute to the scheduler through the backend stderr/status stream. The current quoting helper escapes     quotes and backslashes, but it does not reject or encode LF/CR. As a result, attacker-controlled printer     status text can create a new backend status line beginning with PPD:.

    NOTE: https://github.com/OpenPrinting/cups/security/advisories/GHSA-7hqf-mfhx-7r3vNOTE: Fixed by:
    https://github.com/OpenPrinting/cups/commit/d41cf0616688721e9d435d54118c4c8a36ed596a (v2.4.20)     (CVE-2026-55453)

    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. (CVE-2026-55467)

    When a printer is added or modified with a model PPD, the cupsd scheduler (running as root) calls     copy_model() in scheduler/ipp.c, which writes the driver-generated PPD to a temporary file. The tempfile     path is fully predictable (<TempDir>/<con->number>.ppd, where con->number is the sequential client     connection id) and is opened with open(tempfile, O_WRONLY | O_CREAT | O_TRUNC, 0600) -- without O_EXCL and     without O_NOFOLLOW. TempDir (/var/spool/cups/tmp) is mode 01770 root:lp, i.e. writable by the lp group     that print filters run under. An lp-group process can pre-plant a symlink at thepredicted path pointing at     any root-owned file; root follows the symlink and truncates/overwrites the target, giving an lp - root     arbitrary-file-write primitive. The codebase's own cups/tempfile.c opens temporaries safely with     O_RDWR|O_CREAT|O_EXCL|O_NOFOLLOW; copy_model() is the inconsistent outlier.

    NOTE: https://github.com/OpenPrinting/cups/security/advisories/GHSA-jj94-x3qh-ffp9NOTE: Fixed by:
    https://github.com/OpenPrinting/cups/commit/98adfd855950e806508f961d5438ad32e26aac62 (v2.4.20)     (CVE-2026-55480)

    NOTE: https://github.com/OpenPrinting/cups/security/advisories/GHSA-gq9p-4w7m-2f5gNOTE: Fixed by:
    https://github.com/OpenPrinting/cups/commit/08a8a277ce2a8948a1af33552247a1ac53b72df3 (v2.4.20)     (CVE-2026-61702)

    The cupsUTF32ToUTF8() function in CUPS's cups/transcode.c lacks a source-length bound and can read past     the end of the source buffer, resulting in a heap out-of-bounds read. This is reachable via SNMP supply-     description parsing in backend/snmp-supplies.c with attacker-controlled content. (CVE-2026-87875)

    Two case-insensitive comparisons on request-derived usernames outside the main authorization path in     CUPS's scheduler (printer ACL validation and private-attribute filtering) could allow bypass of username-     based access controls in certain configurations. (CVE-2026-87876)

Tenable has extracted the preceding description block directly from the tested product security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The version of cups installed on the remote host is prior to 2.4.19 / 2.4.20. It is, therefore, affected by multiple vulnerabilities as referenced in the SSA:2026-278-01 advisory.

    New cups packages are available for Slackware 15.0 and -current to fix security issues.

Tenable has extracted the preceding description block directly from the cups security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

There are packages installed that are affected by a vulnerability referenced in the following CVE:

  - Two case-insensitive comparisons on request-derived usernames outside the main authorization path in
    CUPS's scheduler (printer ACL validation and private-attribute filtering) could allow bypass of username-
    based access controls in certain configurations. (CVE-2026-87876)

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - Two case-insensitive comparisons on request-derived usernames outside the main authorization path in     CUPS's scheduler (printer ACL validation and private-attribute filtering) could allow bypass of username-     based access controls in certain configurations. (CVE-2026-87876)

Note that Nessus relies on the presence of the package as reported by the vendor.

ID	Name	Product	Family	Type	Severity
377954	Amazon Linux 2023 : cups, cups-client, cups-devel (ALAS2023-2026-3415)	Nessus	Amazon Linux Local Security Checks	Local	medium
363018	Slackware Linux 15.0 / current cups Multiple Vulnerabilities (SSA:2026-278-01)	Nessus	Slackware Local Security Checks	Local	medium
455432	Echo: cups: security update to 2.4.18-1+e2	Tenable Cloud Security	Echo Local Security Checks	Local	low
455432	Echo: cups: security update to 2.4.18-1+e2	Tenable Self-Hosted Container Security	Echo Local Security Checks	Local	low
344342	Linux Distros Unpatched Vulnerability : CVE-2026-87876	Nessus	Misc.	Local	low

Detections

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CVE-2026-87876

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Tenable Plugins

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