RHSA-2026:8814

CUPS is a standards-based, open-source printing system, and `libcupsfilters` contains the code of the filters of the former `cups-filters` package as library functions to be used for the data format conversion tasks needed in Printer Applications. In CUPS-Filters versions up to and including 1.28.17 and libscupsfilters versions 2.0.0 through 2.1.1, CUPS-Filters's `imagetoraster` filter has an out of bounds read/write vulnerability in the processing of TIFF image files. While the pixel buffer is allocated with the number of pixels times a pre-calculated bytes-per-pixel value, the function which processes these pixels is called with a size of the number of pixels times 3. When suitable inputs are passed, the bytes-per-pixel value can be set to 1 and bytes outside of the buffer bounds get processed. In order to trigger the bug, an attacker must issue a print job with a crafted TIFF file, and pass appropriate print job options to control the bytes-per-pixel value of the output format. They must choose a printer configuration under which the `imagetoraster` filter or its C-function equivalent `cfFilterImageToRaster()` gets invoked. The vulnerability exists in both CUPS-Filters 1.x and the successor library libcupsfilters (CUPS-Filters 2.x). In CUPS-Filters 2.x, the vulnerable function is `_cfImageReadTIFF() in libcupsfilters`. When this function is invoked as part of `cfFilterImageToRaster()`, the caller passes a look-up-table during whose processing the out of bounds memory access happens. In CUPS-Filters 1.x, the equivalent functions are all found in the cups-filters repository, which is not split into subprojects yet, and the vulnerable code is in `_cupsImageReadTIFF()`, which is called through `cupsImageOpen()` from the `imagetoraster` tool. A patch is available in commit b69dfacec7f176281782e2f7ac44f04bf9633cfa.

OpenPrinting CUPS is an open source printing system for Linux and other Unix-like operating systems. In versions 2.4.12 and earlier, when the `AuthType` is set to anything but `Basic`, if the request contains an `Authorization: Basic ...` header, the password is not checked. This results in authentication bypass. Any configuration that allows an `AuthType` that is not `Basic` is affected. Version 2.4.13 fixes the issue.

OpenPrinting CUPS is an open source printing system for Linux and other Unix-like operating systems. In versions 2.4.12 and earlier, an unsafe deserialization and validation of printer attributes causes null dereference in the libcups library. This is a remote DoS vulnerability available in local subnet in default configurations. It can cause the cups & cups-browsed to crash, on all the machines in local network who are listening for printers (so by default for all regular linux machines). On systems where the vulnerability CVE-2024-47176 (cups-filters 1.x/cups-browsed 2.x vulnerability) was not fixed, and the firewall on the machine does not reject incoming communication to IPP port, and the machine is set to be available to public internet, attack vector "Network" is possible. The current versions of CUPS and cups-browsed projects have the attack vector "Adjacent" in their default configurations. Version 2.4.13 contains a patch for CVE-2025-58364.

OpenPrinting CUPS is an open source printing system for Linux and other Unix-like operating systems. Prior to version 2.4.15, a client that connects to cupsd but sends slow messages, e.g. only one byte per second, delays cupsd as a whole, such that it becomes unusable by other clients. This issue has been patched in version 2.4.15.

cups-filters contains backends, filters, and other software required to get the cups printing service working on operating systems other than macos. In cups-filters prior to 1.28.18, by crafting a PDF file with a large `MediaBox` value, an attacker can cause CUPS-Filter 1.x’s `pdftoraster` tool to write beyond the bounds of an array. First, a PDF with a large `MediaBox` width value causes `header.cupsWidth` to become large. Next, the calculation of `bytesPerLine = (header.cupsBitsPerPixel * header.cupsWidth + 7) / 8` overflows, resulting in a small value. Then, `lineBuf` is allocated with the small `bytesPerLine` size. Finally, `convertLineChunked` calls `writePixel8`, which attempts to write to `lineBuf` outside of its buffer size (out of bounds write). In libcupsfilters, the maintainers found the same `bytesPerLine` multiplication without overflow check, but the provided test case does not cause an overflow there, because the values are different. Commit 50d94ca0f2fa6177613c97c59791bde568631865 contains a patch, which is incorporated into cups-filters version 1.28.18.

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.

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.

OpenPrinting CUPS is an open source printing system for Linux and other Unix-like operating systems. In versions 2.4.16 and prior, there is a heap-based buffer overflow in the CUPS scheduler when building filter option strings from job attribute. At time of publication, there are no publicly available patches.

OpenPrinting CUPS is an open source printing system for Linux and other Unix-like operating systems. In versions 2.4.16 and prior, in a network-exposed cupsd with a shared target queue, an unauthorized client can send a Print-Job to that shared PostScript queue without authentication. The server accepts a page-border value supplied as textWithoutLanguage, preserves an embedded newline through option escaping and reparse, and then reparses the resulting second-line PPD: text as a trusted scheduler control record. A follow-up raw print job can therefore make the server execute an attacker-chosen existing binary such as /usr/bin/vim as lp. At time of publication, there are no publicly available patches.

OpenPrinting CUPS is an open source printing system for Linux and other Unix-like operating systems. In versions 2.4.16 and prior, a local unprivileged user can coerce cupsd into authenticating to an attacker-controlled localhost IPP service with a reusable Authorization: Local ... token. That token is enough to drive /admin/ requests on localhost, and the attacker can combine CUPS-Create-Local-Printer with printer-is-shared=true to persist a file:///... queue even though the normal FileDevice policy rejects such URIs. Printing to that queue gives an arbitrary root file overwrite; the PoC below uses that primitive to drop a sudoers fragment and demonstrate root command execution. At time of publication, there are no publicly available patches.

OpenPrinting CUPS is an open source printing system for Linux and other Unix-like operating systems. In versions 2.4.16 and prior, an integer underflow vulnerability in _ppdCreateFromIPP() (cups/ppd-cache.c) allows any unprivileged local user to crash the cupsd root process by supplying a negative job-password-supported IPP attribute. The bounds check only caps the upper bound, so a negative value passes validation, is cast to size_t (wrapping to ~2^64), and is used as the length argument to memset() on a 33-byte stack buffer. This causes an immediate SIGSEGV in the cupsd root process. Combined with systemd's Restart=on-failure, an attacker can repeat the crash for sustained denial of service.

OpenPrinting CUPS is an open source printing system for Linux and other Unix-like operating systems. In versions 2.4.16 and prior, a use-after-free vulnerability exists in the CUPS scheduler (cupsd) when temporary printers are automatically deleted. cupsdDeleteTemporaryPrinters() in scheduler/printers.c calls cupsdDeletePrinter() without first expiring subscriptions that reference the printer, leaving cupsd_subscription_t.dest as a dangling pointer to freed heap memory. The dangling pointer is subsequently dereferenced at multiple code sites, causing a crash (denial of service) of the cupsd daemon. With heap grooming, this can be leveraged for code execution.