CUPS vulnerabilities affecting Linux, Unix systems can lead to RCE
Vulnerabilities mentionedAll →
| CVE | Vulnerability | CVSS | EPSS | Flags | Affected | Exposure | Published |
|---|---|---|---|---|---|---|---|
| CVE-2024-47076 | Unsanitized IPP attribute injection in OpenPrinting libcupsfilters (CWE-20) OpenPrinting's libcupsfilters, the library providing CUPS filter functionality for printer data-format conversion, fails to sanitize IPP attributes returned from IPP servers in its cfGetPrinterAttributes5 function (CWE-20, CVSS 8.6). The flaw is triggered when a system running CUPS contacts an attacker-controlled or untrusted IPP server and uses the returned attributes, for example to generate a PPD file, allowing attacker-controlled data to flow into the rest of the CUPS system. On its own this yields high-integrity attacker data injection (per the CVSS vector, no direct confidentiality or availability loss), but it is one of several CUPS flaws disclosed together in late September 2024 that, when chained under certain conditions, can result in remote code execution on Linux and Unix systems. Any system running libcupsfilters is affected; CUPS and its filter libraries ship by default with most major Linux distributions, and public internet scans around disclosure found roughly 75,000 hosts exposing the IPP service (TCP 631) directly to the internet. Proof-of-concept details are public (an EvilSocket writeup and the OpenPrinting GitHub advisory GHSA-w63j-6g73-wmg5), the flaw is not yet in CISA KEV, and EPSS assigns a 77.6% probability of exploitation within 30 days, though no confirmed in-the-wild exploitation appears in the provided data. Do: Upgrade libcupsfilters to the patched release identified in the OpenPrinting advisory GHSA-w63j-6g73-wmg5 (fixed in libcupsfilters 2.1.0), applying your distribution's updated cups-filters/CUPS packages; also install the companion CUPS component fixes released the same week, since this flaw is typically chained with other CUPS bugs (notably in cups-browsed) for remote code execution. Until patched, restrict or disable exposure of the IPP service (TCP 631) to untrusted networks and avoid creating or refreshing printer queues from untrusted or mDNS-advertised IPP servers. | 8.6 | 78% | PoC ×2 |
| masstens of millions of Linux/Unix systems ship the vulnerable library; ~75,000 hosts expose IPP (TCP 631) directly to the internet per public scans | |
| CVE-2024-47175 | Unsanitized IPP input in OpenPrinting libppd enables RCE chain on Linux CUPS CVE-2024-47175 is an improper input validation flaw (CWE-20) in OpenPrinting's libppd: the ppdCreatePPDFromIPP2 function fails to sanitize IPP attributes when writing them into a generated PPD buffer. When this unsanitized, attacker-controlled input flows through the CUPS print pipeline — for example via the cups-browsed entry point abused in CVE-2024-47176, in combination with functions such as cfGetPrinterAttributes5 — it can ultimately be executed by Foomatic print filters, giving remote code execution. Affected systems are Linux/Unix hosts running the CUPS printing stack with vulnerable libppd components, which includes widely used distributions such as Debian and, per press coverage, most other major Linux distros. Exploitation status: public proofs of concept and researcher write-ups exist, the flaw carries a high EPSS score (63.6% probability of exploitation within 30 days, 99th percentile) and warnings about abuse including DDoS, but it is not yet in CISA's KEV catalog, so no confirmed widespread in-the-wild exploitation is documented in the available data. Do: Install your distribution's security updates — upgrade libppd to the patched release (2.1b1 or later, per the OpenPrinting advisory GHSA-7xfx-47qg-grp6) and apply the matching cups/cups-filters fixes. As interim mitigation, disable or stop cups-browsed if not needed and block or restrict inbound UDP 631 (and IPP/port 631 generally) from untrusted networks, particularly on internet-facing hosts. Check whether CUPS is running and reachable on your systems and whether configured printers rely on Foomatic filters, which the RCE chain requires. | 9.8 | 64% | PoC ×2 |
| largetens of thousands of internet-exposed CUPS hosts (roughly 75,000 per public internet-wide scans at disclosure), on top of a far larger install base of Linux… | |
| CVE-2024-47176 | Unauthenticated RCE chain in OpenPrinting cups-browsed (CVE-2024-47176) CVE-2024-47176 is a flaw in cups-browsed, the network printer auto-discovery component of the OpenPrinting CUPS printing stack shipped with most major Linux and Unix distributions, which binds to UDP port 631 on all interfaces (INADDR_ANY) and therefore accepts and trusts unauthenticated packets from any source. A remote attacker can send a crafted browse/IPP packet that makes cups-browsed issue a Get-Printer-Attributes IPP request to an attacker-controlled URL. On its own this flaw is rated Medium (5.3), but chained with companion flaws in libcupsfilters (CVE-2024-47076), libppd (CVE-2024-47175), and cups-filters (CVE-2024-47177) it enables unauthenticated arbitrary command execution when a user prints to the attacker's malicious printer; the exposure has also been noted as abusable for DDoS amplification. Any Linux/Unix system running cups-browsed with UDP/631 reachable from an untrusted network is affected. No confirmed widespread in-the-wild exploitation has been reported and the flaw is not yet in CISA's KEV, but public proofs of concept exist and EPSS assigns a ~51% probability of exploitation within 30 days (99th percentile). Do: Update cups-browsed and the companion cups-filters/libcupsfilters/libppd packages to the patched releases published by OpenPrinting and your distribution alongside the September 2024 advisories (see GHSA-rj88-6mr5-rcw8). If patched packages are not yet available, stop or disable the cups-browsed service, or firewall inbound UDP port 631 from untrusted networks and ensure it binds only to localhost where network printer discovery is not needed. Audit whether cups-browsed is running and whether UDP/631 is reachable from the internet, and treat any network-reachable CUPS host as a candidate for the full RCE chain. | 5.3 | 51% | PoC ×2 |
| massmillions of Linux/Unix installations (cups-browsed ships in the default print stack of major distributions), of which only on the order of tens of thousands of… | |
| CVE-2024-47177 | Rejected reason: ** REJECT ** DO NOT USE THIS CANDIDATE NUMBER. Rejected reason: ** REJECT ** DO NOT USE THIS CANDIDATE NUMBER. ConsultIDs: CVE-2024-47076, CVE-2024-47175, CVE-2024-47176. Reason: This candidate is a duplicate of CVE-2024-47076, CVE-2024-47175, and CVE-2024-47176. Notes: All CVE users should reference CVE-2024-47076, CVE-2024-47175, and/or CVE-2024-47176 instead of this candidate. This CVE was issued to a vulnerability that is dependent on CVE-2024-47076, CVE-2024-47175, and CVE-2024-47176. According to rule 4.2.15 of the CVE CNA rules, \"CNAs MUST NOT assign a different CVE ID to a Vulnerability that is fully interdependent with another Vulnerability. The Vulnerabilities are effectively the same single Vulnerability and MUST use one CVE ID. NVD description · AI analysis pending | — | — | — | — |
Full article606 words · extracted from helpnetsecurity.com · click to collapse
After much hyping and following prematurely leaked information by a third party, security researcher Simone Margaritelli has released details about four zero-day vulnerabilities in the Common UNIX Printing System (CUPS) that can be abused by remote, unauthenticated attackers to achieve code execution on vulnerable Linux and Unix-like sistems.
The CUPS vulnerabilities
CUPS is an open-source printing system that allows a computer on which is installed to act as a print server. It is developed by OpenPrinting, a free software organization under The Linux Foundation.
CUPS redirects and manages print jobs submitted by client computers to local or network-attached printers via the Internet Printing Protocol (IPP).
The vulnerabilities discovered by Margaritelli (aka EvilSocket) affect several CUPS components/packages:
- CVE-2024-47176, in the cups-browsed (up to version 2.0.1) helper daemon, which allows attackers to submit packets via the IPP default port (UDP 631) and trick it to request arbitrary, attacker-controlled URLs
- CVE-2024-47076, in libcupsfilters (up to version 2.1b1), which allows attackers to pass malicious data to other CUPS components
- CVE-2024-47175, in libppd (up to version 2.1b1), which allows attackers to inject malicious data in the temporary PPD file to pass to CUPS components
- CVE-2024-47177, in cups-filters (up to version 2.0.1) , which allows attackers to execute arbitrary commands via the FoomaticRIPCommandLine PPD parameter
By chaining some of these flaws, “a remote unauthenticated attacker can silently replace existing printers’ (or install new ones) IPP URLs with a malicious one, resulting in arbitrary command execution (on the computer) when a print job is started (from that computer),” Margaritelli explained.
To trigger command execution, though, a user must launch a print job on the malicious printer.
“According to the researcher’s disclosure blog, affected systems are exploitable from the public internet, or across network segments, if UDP port 631 is exposed and the vulnerable service is listening,” Rapid7 researchers noted.
Who’s affected and what to do?
CUPS is used by most Linux distros and some BSD ones. Some enable it by default, and some do not.
OpenPrinting has published some fixes and a temporary workaround for CVE-2024-47176, and the various distros are working on porting them.
While waiting for updated CUPS packages, Margaritelli advises disabling and/or removing the cups-browsed service and “in case your system can’t be updated and for some reason you rely on this service, block[ing] all traffic to UDP port 631 and possibly all DNS-SD traffic.”
Red Hat has explained how its customers can check whether cups-browsed is running on their system and how to stop it from running and re-starting on reboot.
Margaritelli says he found hundreds of thousands of devices of potentially vulnerable devices. Tenable researchers tried using Shodan and FOFA (search engines for internet-connected devices) and found “a significant number of hosts that do appear to be internet-accessible with a majority of the results using the default port, 631.”
So far, there have been no reports of these flaws being leveraged by attackers in the wild, but proof-of-concept (PoC) exploits – including one by Margaritelli – are public.
“From what we’ve gathered, these flaws are not at a level of a Log4Shell or Heartbleed,” Tenable senior staff research engineer Satnam Narang told Help Net Security.
“For organizations that are honing in on these latest vulnerabilities, it’s important to highlight that the flaws that are most impactful and concerning are the known vulnerabilities that continue to be exploited by advanced persistent threat groups with ties to nation states, as well as ransomware affiliates that are pilfering from corporations millions of dollars each year.”
Subscribe to our breaking news e-mail alert to never miss out on the latest breaches, vulnerabilities and cybersecurity threats. Subscribe here!
Text extracted automatically; images, tables and formatting may be missing. Original: https://www.helpnetsecurity.com/2024/09/27/cups-vulnerabilities/