From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-53282][LOW] x86/kexec: Push kjump return address even for non-kjump kexec Date: Fri, 26 Jun 2026 16:20:26 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-53282 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: 0 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: b0bd7a850e1f082560959707dbf57b0402071646 List-Id: CVE: CVE-2026-53282 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: x86/kexec: Push kjump return address even for non-kjump kexec Commit: b0bd7a850e1f082560959707dbf57b0402071646 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b0bd7a850e1f082560959707dbf57b0402071646 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53282 Analysis date: Fri, 26 Jun 2026 16:20:26 -0400 ActionableScore: 0 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate / Low-like Manual review required: NO Summary: A non-kjump x86 kexec transition can fail because kexec-tools purgatory expects a return address word on the stack, causing a fault and denial of service for the kexec operation, but exploitation requires host administrative kexec privileges. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53282 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53282 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-2026-53282 LOW CHECK Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';CWE-665;CWE-703;CWE-754;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.4';DESCR 'The x86 kexec path can fail during a normal non-kjump kexec because the purgatory code from kexec-tools expects a return address word on the stack even when preserve-context kjump is not used. If that word is missing, purgatory may fault while checking whether kexec_jump_back_entry should be set, causing the kexec transition to fail. For the CVSS the PR:H is used because triggering this path normally requires administrative kexec privileges such as CAP_SYS_BOOT or root access. The issue is not network reachable and is not triggered by packet traffic or an unprivileged local interface. Impact is denial of service limited to failed kexec or reboot transition, with no evidence of confidentiality impact, integrity impact, UAF, OOB write, or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 0) SKIP CVE-2026-53282 SKIP No affected files built, so skip this CVE NO - - unknown MAYBE OOB DANGER SIMPLEFIX KERNEL_PANIC_PLUS_UAF HARDWARE DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=0 ## 1. ActionableScore * Conservative score: 0 * Paranoid score: 0 * Final recommended bucket: **Ordinary Moderate / Low-like** ## 2. Signal breakdown * Reliable kernel crash / strong DoS: +1 The purgatory code may fault during a non-kjump kexec transition because it expects a return address word on the stack. * Requires admin/root/CAP_SYS_BOOT in typical deployments: -2 Triggering kexec normally requires root or CAP_SYS_BOOT on the host. * Rare or difficult-to-reach subsystem/configuration: -1 This is limited to the kexec transition path, not a common syscall, network, filesystem, or packet-processing path. * No memory corruption: +0 The patch does not indicate UAF, double-free, OOB write, arbitrary write, object lifetime corruption, or page-cache corruption. * No confidentiality or integrity impact: +0 The observed effect is failed kexec transition, not data disclosure or privilege escalation. Score is floored at 0. ## 3. Reachability analysis The bug is reachable only by initiating a kexec path. In normal deployments this requires administrative privileges such as root or CAP_SYS_BOOT. Containers and user namespaces usually do not provide meaningful access to host kexec, and lockdown or distro policy may restrict it further. There is no realistic network trigger and no unprivileged local interface shown by the patch. ## 4. Severity interpretation This behaves like a privileged local reliability or availability issue, not an Important-class vulnerability. The realistic impact is failure of a kexec reboot or crash-recovery transition. Theoretical memory corruption is not supported by the patch context, because the issue is an expected stack word missing for purgatory detection logic rather than attacker-controlled overwrite, UAF, or stale object reuse. ## 5. One-sentence report phrase A non-kjump x86 kexec transition can fail because kexec-tools purgatory expects a return address word on the stack, causing a fault and denial of service for the kexec operation, but exploitation requires host administrative kexec privileges. ## 6. Manual review recommendation NO MANUAL CHECK NEEDED This can be auto-closed for security triage unless the environment treats kexec failure as operationally critical. There is no supported LPE, memory corruption, or remote exposure signal. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: x86/kexec: Push kjump return address even for non-kjump kexec Commit: b0bd7a850e1f082560959707dbf57b0402071646 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b0bd7a850e1f082560959707dbf57b0402071646 Commit description: The version of purgatory code shipped by kexec-tools attempts to look above the top of its stack to find a return address for a kjump, even in a non-kjump kexec. After the commit in Fixes: the word above the stack might not be there, leading to a fault (which is at least now caught by my exception-handling code in kexec). That commit fixed things for the actual kjump path, but no longer "gratuitously" pushes the unused return address to the stack in the non-kjump path. Put that *back* in the non-kjump path, to prevent purgatory from crashing when trying to access it. Fixes: 2cacf7f ("x86/kexec: Fix stack and handling of re-entry point for ::preserve_context") Reported-by: Rohan Kakulawaram Signed-off-by: David Woodhouse Signed-off-by: Borislav Petkov (AMD) Acked-by: Dave Hansen Tested-by: Rohan Kakulawaram Cc: Link: https://patch.msgid.link/32d627134143ffd957891cb697138e839c623211.camel@infradead.org Signed-off-by: Greg Kroah-Hartman Changed files: arch/x86/kernel/relocate_kernel_64.S 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=b0bd7a850e1f082560959707dbf57b0402071646 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53282 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53282 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:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L The Best / paranoid CVSS vector: AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 4.4 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: unknown Paranoid ActionableScore: 0 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).