From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-46167][LOW] usb: usblp: fix uninitialized heap leak via LPGETSTATUS ioctl Date: Thu, 28 May 2026 11:19:34 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-46167 X-AL-KERNEL-Priority: LOW X-AL-KERNEL-Severity: LOW X-AL-KERNEL-Base-Severity: LOW X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 1 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: d06d937b0a4cdb8867f04275c8100a8b943da31a List-Id: CVE: CVE-2026-46167 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: usb: usblp: fix uninitialized heap leak via LPGETSTATUS ioctl Commit: d06d937b0a4cdb8867f04275c8100a8b943da31a Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d06d937b0a4cdb8867f04275c8100a8b943da31a Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46167 Analysis date: Thu, 28 May 2026 11:19:34 -0400 ActionableScore: 1 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate / Low-like Manual review required: NO Summary: `usblp` could expose one stale kernel heap byte through `LPGETSTATUS` when a malformed USB printer returned zero bytes before the status buffer had been initialized. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-46167 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46167 The original announcement does not normally provide a security severity estimate, CVSS assessment, or enough information to determine whether the reported kernel bug represents a practically relevant security issue. This report was generated by AL-KERNEL, an AI-assisted Linux kernel vulnerability analysis system developed by Alexander Larkin. It combines an autonomous classifier with LLM-assisted technical analysis and a separate ActionableScore mechanism. The purpose of this report is to prioritize Linux kernel CVEs before manual review, identify cases that require prompt investigation, and support automatic closure of issues that are unlikely to have meaningful security impact. Published priority for this report: LOW Manual review required: NO A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-46167 LOW CHECK Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N';*CWE-457;*CWE-200;CWE-908;CWE-665;Other CVSS 'AV:P/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N';BEST CVSS score: '2.5';DESCR 'usblp allocated the printer status buffer with kmalloc and did not initialize it before the first LPGETSTATUS ioctl. If a malformed USB printer returns zero bytes for the one byte status request, the ioctl can copy a stale heap byte to userspace after sign extension into an int. For the CVSS the PR:L is used for the paranoid score because a local user needs access to the usblp device node or an equivalent USB passthrough context. The main attack model is physical or local device access, not network reachability. Impact is limited kernel information disclosure only, with no supported memory corruption, write primitive, or privilege escalation path.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1) MAYBE USB LEAK HARDWARE LINUS - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=1 ## 1. ActionableScore * Conservative score: 1 * Paranoid score: 1 * Final recommended bucket: **Ordinary Moderate / Low-like**:: ## 2. Signal breakdown Positive signals: * Confidentiality impact plausible: +1. `LPGETSTATUS` may copy one stale heap byte to userspace if the status buffer was never initialized. * Local user/device access trigger: +1. A local user needs access to the `usblp` device node and the malformed printer behavior. Negative / limiting signals: * Physical or local USB-device condition: -2. The main attacker model requires a malicious USB printer or USB passthrough context. * No memory corruption. This is an uninitialized heap byte disclosure, not UAF, OOB write, double free, or arbitrary write. * No privilege escalation. * No network reachability. * Very constrained leak size. The directly described leak is one stale byte through a status ioctl. ## 3. Reachability analysis The issue is triggered when a malformed USB printer returns zero bytes for a one-byte status request and a local process calls `LPGETSTATUS`. The attacker generally needs physical USB device control, USB passthrough, or control of the attached printer. A local unprivileged user may only exploit it if they can open the `usblp` device node. Containers matter only if USB printer passthrough or the `usblp` node is delegated into the container. ## 4. Severity interpretation This behaves like Low / ordinary Moderate. The realistic impact is a very small kernel heap information disclosure to a local ioctl caller. There is no supported memory corruption, integrity impact, availability impact, or privilege escalation path. ## 5. One-sentence report phrase `usblp` could expose one stale kernel heap byte through `LPGETSTATUS` when a malformed USB printer returned zero bytes before the status buffer had been initialized. ## 6. Manual review recommendation NO MANUAL CHECK NEEDED This can generally be auto-closed for urgent security triage because it is a tiny physical/local USB information leak with no memory corruption or LPE evidence. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: usb: usblp: fix uninitialized heap leak via LPGETSTATUS ioctl Commit: d06d937b0a4cdb8867f04275c8100a8b943da31a Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d06d937b0a4cdb8867f04275c8100a8b943da31a Commit description: Just like in a previous problem in this driver, usblp_ctrl_msg() will collapse the usb_control_msg() return value to 0/-errno, discarding the actual number of bytes transferred. Ideally that short command should be detected and error out, but many printers are known to send "incorrect" responses back so we can't just do that. statusbuf is kmalloc(8) at probe time and never filled before the first LPGETSTATUS ioctl. usblp_read_status() requests 1 byte. If a malicious printer responds with zero bytes, *statusbuf is one byte of stale kmalloc heap, sign-extended into the local int status, which the LPGETSTATUS path then copy_to_user()s directly to the ioctl caller. Fix this all by just zapping out the memory buffer when allocated at probe time. If a later call does a short read, the data will be identical to what the device sent it the last time, so there is no "leak" of information happening. Cc: Pete Zaitcev Assisted-by: gkh_clanker_t1000 Cc: stable Link: https://patch.msgid.link/2026042011-shredder-savage-48c6@gregkh Signed-off-by: Greg Kroah-Hartman Changed files: drivers/usb/class/usblp.c Diff excerpt: Not included in this email. See the upstream URL for the full patch. Full patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d06d937b0a4cdb8867f04275c8100a8b943da31a ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-46167 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46167 The original CVE announcement normally does not include a security-level estimate. In particular, it may not contain a CVSS assessment, an impact level, or enough information to determine whether the reported bug is a practically relevant security issue. One purpose of this parallel CVE list is to provide that missing technical and prioritization information. The original goal of the AL-KERNEL project was to prioritize Linux kernel CVE analysis automatically before manual review. The system can also help identify non-security issues that may be suitable for automatic closure. This report was generated by AL-KERNEL, an AI-assisted Linux kernel vulnerability analysis system developed by Alexander Larkin. The first analysis stage combines an autonomous classifier with additional LLM-based analysis. The autonomous classifier runs locally on a CPU and is based on a backpropagation neural network. Together, these mechanisms produce a technical vulnerability description, identify likely weakness types, estimate CVSS severity, and provide input for ActionableScore. Two CVSS estimates are retained because incomplete kernel vulnerability information often permits more than one defensible interpretation: Conservative CVSS vector: AV:P/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N The Best / paranoid CVSS score: 2.5 The conservative vector represents a lower-impact interpretation. The Best/paranoid vector intentionally represents a plausible upper-bound interpretation and should not automatically be treated as demonstrated real-world impact. CVSS may also need to be adjusted for a particular Linux deployment, because actual reachability, privileges, enabled kernel configuration, hardware, namespaces, exposed device nodes, and other environmental conditions can differ significantly between systems. A separate ActionableScore mechanism evaluates practical remediation urgency. Its analysis may include reachability, attack prerequisites, subsystem exposure, memory-corruption characteristics, denial-of-service reliability, and possible confidentiality, integrity, or privilege-escalation impact. Conservative ActionableScore: unknown Paranoid ActionableScore: 1 The final base severity is taken directly from the second tab-separated field of the AL-KERNEL classification result. ActionableScore does not replace or independently override that final AL-KERNEL decision, and if ActionableScore adjusted impact level of ALKERNEL, then you would see self-readable flags above like INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7. For an AL-KERNEL result of MODERATE, this report uses the following additional presentation split: ActionableScore below 5 -> MODERATE REGULAR ActionableScore 5 or more -> MODERATE 7.0 The distinction between MODERATE REGULAR and MODERATE 7.0 makes it possible to identify Moderate issues that should receive manual analysis and fixes before lower-priority MODERATE REGULAR issues. In many cases, MODERATE REGULAR fixes may wait for a later rebase or routine update. There is one override in which MODERATE REGULAR becomes MODERATE 7.0 even when the ActionableScore is below 5. When the AL-KERNEL result contains the KPANIC flag, a MODERATE result is always presented as MODERATE 7.0. The KPANIC flag selected with few regexps without usage of AI at all, so it helps to detect cases when Kernel Crash happens and similar (to filter False-Negative results from the LLM usage). KPANIC indicates that a reliable kernel crash, kernel panic, or similarly serious kernel availability impact was identified by the classification workflow. AL-KERNEL base severity for this report: LOW KPANIC detected for this report: NO Published priority for this report (same as in Subject): LOW These results are intended to support engineering triage. They are machine-generated estimates, and cases marked for manual review should be validated by a human security engineer before final disposition. For more info read docs linked from here: https://kernelcve.org/ (and you can submit you own patch there to generate such a report for non-existant CVE-id yet). Note that in many cases this AI tool selects higher severity, than real is (means you can expect Importants instead of Moderate 7.0 or Moderates 7.0 instead of regular Moderates). If you see such cases, please use reply email interface to add additional manual analyses info to this particular CVE. And please, please, let me know when you see Lows instead of Importants or Important instead of Low (because particular for such cases I need to tune this AI tool to make it better for this one and next similar). My contact email for such notifications is alexanjelausa@gmail.com (and both send reply to CVE record itself too and see "reply" button below for howto reply).