Cups: null pointer dereference via embedded job ticket comments allows remote denial of service

Package updates are available for Amazon Linux 2023 that fix the following vulnerabilities: CVE-2026-87876: 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-2026-87875: 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-2026-61702: NOTE: https://github.com/OpenPrinting/cups/security/advisories/GHSA-gq9p-4w7m-2f5g NOTE: Fixed by: https://github.com/OpenPrinting/cups/commit/08a8a277ce2a8948a1af33552247a1ac53b72df3 (v2.4.20) CVE-2026-55480: 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 the predicted 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-ffp9 NOTE: Fixed by: https://github.com/OpenPrinting/cups/commit/98adfd855950e806508f961d5438ad32e26aac62 (v2.4.20) CVE-2026-55467: 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-2026-55453: 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-7r3v NOTE: Fixed by: https://github.com/OpenPrinting/cups/commit/d41cf0616688721e9d435d54118c4c8a36ed596a (v2.4.20) CVE-2026-107890: 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-2026-107888: 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-2026-107886: 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-2026-107885: 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-2026-107655: 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-2026-105326: 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.

Where it's fixed