From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-80827][MODERATE REGULAR] USB: serial: option: fix slab OOB read in interrupt URB callback Date: Fri, 04 Sep 2026 17:41:55 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-80827 X-AL-KERNEL-Priority: MODERATE REGULAR X-AL-KERNEL-Severity: MODERATE REGULAR X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 2 X-AL-KERNEL-ActionableScore-Lower: 1 X-AL-KERNEL-Commit: fbe60fd2abc8a5561f39719a41ad9a01b5d8e567 List-Id: CVE: CVE-2026-80827 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: USB: serial: option: fix slab OOB read in interrupt URB callback Commit: fbe60fd2abc8a5561f39719a41ad9a01b5d8e567 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fbe60fd2abc8a5561f39719a41ad9a01b5d8e567 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80827 Analysis date: Fri, 04 Sep 2026 17:41:55 -0400 ActionableScore: 2 ActionableScore lower bound: 1 Actionable bucket: Ordinary Moderate / Low-like, manual review due kernel OOB read Manual review required: YES Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-80827 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80827 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: MODERATE REGULAR Manual review required: YES A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-80827 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-80827 CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:P/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:H';CWE-125;*CWE-20;CWE-129;CWE-125;Other CVSS 'AV:P/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:L';BEST CVSS score: '5.4';DESCR 'A slab out-of-bounds read exists in the USB serial option interrupt URB callback because option_instat_callback can access data at offset sizeof(*req_pkt) without first proving that the completed URB contains that byte. A malicious or malformed USB device can declare an interrupt IN endpoint with wMaxPacketSize 8 and return a short or boundary sized packet, causing the driver to read one byte beyond the kmalloc-8 buffer. For the CVSS the PR:N because the attacker does not need software privileges on the victim when using a malicious USB device, but UI:R is required because the device must be attached or otherwise presented to the host. The issue is not directly network reachable in normal deployments and is mainly a physical or local device attack surface. Impact is at least limited confidentiality exposure from an invalid kernel read and possible denial of service on hardened or debug kernels. In the paranoid score, limited integrity impact is kept possible because the out-of-bounds byte is interpreted as modem signal state, but there is no evidence of an arbitrary write primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like, manual review due kernel OOB read (with actual score 2) YES READ OOB USB INIT PRINTF-TTY ERRORPATH HARDWARE LINUS PACKET DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=2 ActionableScoreLower=1 1. ActionableScore * Conservative score: 1 * Paranoid score: 2 * Final recommended bucket: **Ordinary Moderate / Low-like, manual review due kernel OOB read**:: 2. Signal breakdown * Confidentiality impact plausible: +1. The bug is a one byte slab OOB read from a kmalloc-8 interrupt URB buffer. * Availability impact realistic: +1 in the paranoid score only. A crash is plausible mainly on hardened or debug kernels such as KASAN or panic-on-oops style configurations, but not strongly demonstrated as reliable on normal production kernels. * Physical-only or rare hardware-only condition: -2. The realistic attacker is a malicious or malformed USB device, or an equivalent local USB device presentation path. * Weak corruption only: +0. This is a read-only OOB access. There is no OOB write, UAF, double free, type confusion, callback overwrite, or attacker-controlled reclaim primitive shown. 3. Reachability analysis A malicious USB device can trigger the bug by exposing an interrupt IN endpoint with wMaxPacketSize 8 and returning a short or boundary-sized packet that reaches option_instat_callback(). No software privileges on the victim are needed for the malicious-device model, but user interaction or physical/device presentation is required. This is not network reachable in normal deployments. The affected driver is old and widely available, but practical exposure depends on whether such a USB serial option device can be attached and bound to the driver. 4. Severity interpretation This behaves like a low-end to ordinary Moderate kernel memory-safety issue. The theoretical issue is a slab OOB read with possible limited information exposure and possible crash under hardened/debug configurations. Realistic exploitation evidence is weak because the read is one byte, read-only, physically mediated, and does not show a stronger corruption or privilege-escalation primitive. 5. One-sentence report phrase A slab OOB read in the USB serial option interrupt URB callback can be triggered by a malicious USB device with a small interrupt endpoint packet, causing limited kernel memory exposure and possible DoS on hardened systems. 6. Manual review recommendation MANUAL CHECK REQUIRED. YES REQUIRES MANUAL CHECK. This is not an Important-class candidate by default, but it is still a kernel slab OOB read and should not be auto-closed without confirming product exposure to untrusted USB devices. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: USB: serial: option: fix slab OOB read in interrupt URB callback Commit: fbe60fd2abc8a5561f39719a41ad9a01b5d8e567 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fbe60fd2abc8a5561f39719a41ad9a01b5d8e567 Commit description: The interrupt URB buffer is allocated in setup_port_interrupt_in() based on the endpoint's wMaxPacketSize: buffer_size = usb_endpoint_maxp(epd); port->interrupt_in_buffer = kmalloc(buffer_size, GFP_KERNEL); When a USB device declares wMaxPacketSize = 8 on its interrupt IN endpoint, the buffer is allocated from kmalloc-8 cache (exactly 8 bytes). If the device sends a short packet (actual_length < wMaxPacketSize), the URB completes with status == 0 and the callback proceeds to read: data[sizeof(struct usb_ctrlrequest)] which evaluates to data[8], accessing 1 byte beyond the allocated 8-byte buffer. This results in a slab out-of-bounds read. Fix this by adding the missing bounds check: first verify that the actual length is large enough to contain the struct usb_ctrlrequest header before accessing req_pkt->bRequestType and req_pkt->bRequest, and then verify that there is an additional byte for the modem signal state before reading data[sizeof(struct usb_ctrlrequest)] inside the conditional. Use sizeof(*req_pkt) instead of sizeof(struct usb_ctrlrequest) for consistency. Assisted-by: Claude:deepseek-v4-pro Signed-off-by: Jiale Yao Fixes: 58cfe91 ("[PATCH] USB: add Option Card driver") Cc: stable@vger.kernel.org # v2.6.12 [ johan: use dev_err(); split signals declaration and initialisation ] Signed-off-by: Johan Hovold Signed-off-by: Greg Kroah-Hartman Changed files: drivers/usb/serial/option.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=fbe60fd2abc8a5561f39719a41ad9a01b5d8e567 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-80827 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80827 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:N/UI:R/S:U/C:L/I:N/A:L The Best / paranoid CVSS vector: AV:P/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:H The Best / paranoid CVSS score: 5.4 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: 1 Paranoid ActionableScore: 2 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: MODERATE KPANIC detected for this report: NO Published priority for this report (same as in Subject): MODERATE REGULAR 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).