From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-46303][MODERATE REGULAR] isofs: validate Rock Ridge CE continuation extent against volume size Date: Mon, 08 Jun 2026 14:52:03 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-46303 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: 4 X-AL-KERNEL-ActionableScore-Lower: 3 X-AL-KERNEL-Commit: 8356fb821016797f5677cbeee5ddc0d32a95b4be List-Id: CVE: CVE-2026-46303 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: isofs: validate Rock Ridge CE continuation extent against volume size Commit: 8356fb821016797f5677cbeee5ddc0d32a95b4be Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8356fb821016797f5677cbeee5ddc0d32a95b4be Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46303 Analysis date: Mon, 08 Jun 2026 14:52:03 -0400 ActionableScore: 4 ActionableScore lower bound: 3 Actionable bucket: Borderline, manual review recommended Manual review required: YES Summary: A crafted Rock Ridge ISO image can reference CE continuation blocks outside the mounted ISO volume, creating a narrow local information disclosure path through readlink() when desktop automount or delegated ISO mounting is available. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-46303 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46303 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-2026-46303 MODERATE CHECK Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:L';*CWE-20;*CWE-200;CWE-668;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N';BEST CVSS score: '4.4';DESCR 'Rock Ridge CE continuation extent is trusted without checking that the referenced block is inside the ISO 9660 volume. A crafted ISO image can set cont_extent to an out-of-range block or to an in-range block that belongs to adjacent data on the same block device. Out-of-range reads normally fail cleanly through sb_bread and EIO, so this is not a memory corruption issue. The main security concern is a narrow confidentiality exposure where adjacent data may be parsed as Rock Ridge records and limited SL text may become visible through readlink(). For the CVSS the PR:L is used because reliable triggering can be available to a local logged in user when desktop automount or udisks2 permits mounting removable ISO media, while CAP_SYS_ADMIN would be required on more locked down systems. The issue is not network reachable. Impact is mainly limited information disclosure with at most minor availability impact for the malformed mounted filesystem.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended (with actual score 4) MAYBE OOB DISK LEAK HARDWARE LINUS INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=4 ActionableScoreLower=3 ## 1. ActionableScore * Conservative score: 3 * Paranoid score: 4 * Final recommended bucket: **Borderline, manual review recommended**:: ## 2. Signal breakdown * Local unprivileged trigger: +1 A local user may be able to trigger this by providing a crafted ISO image to a desktop automount path such as udisks2. In locked down server deployments, CAP_SYS_ADMIN mount access may be required. * Filesystem/storage metadata reachable by an unprivileged local user: +1 The malformed Rock Ridge CE metadata is attacker controlled through the ISO filesystem image. * Confidentiality impact plausible: +1 The unchecked cont_extent may point outside the ISO volume but still within the same block device, allowing a narrow possible disclosure path if adjacent data is parsed as Rock Ridge records and exposed through readlink(). * Availability impact realistic, paranoid only: +1 Out of range reads return EIO cleanly, so no strong DoS is demonstrated. A minor availability impact for the malformed mounted filesystem is plausible but not system wide. * No memory corruption signal: +0 The commit explicitly indicates sb_bread() returns NULL cleanly for out of range blocks, and the patch only adds a bounds check against s_nzones. * No remote/network reachability: +0 This is a crafted local filesystem image mount path, not a network parser. ## 3. Reachability analysis A crafted ISO image is required. On desktop systems, a local logged in user may trigger the path through removable media or udisks2 automount, so PR:L is the practical paranoid interpretation. On hardened servers, mounting ISO images usually requires CAP_SYS_ADMIN, which would lower practical exposure. Containers and namespaces may matter only if ISO mounting or a mount helper is delegated into the container. The affected path is not network reachable and depends on ISOFS plus Rock Ridge parsing being used. ## 4. Severity interpretation This behaves like a low to borderline Moderate information disclosure issue, not an Important kernel memory corruption bug. The realistic impact is a narrow cross-volume read primitive where only data that parses into usable Rock Ridge SL text may reach userspace. There is no evidence of UAF, OOB write, arbitrary write, page-cache corruption, or privilege escalation. Manual review is still reasonable because the bug crosses a filesystem volume boundary and the confidentiality impact depends on block-device layout and automount policy. ## 5. One-sentence report phrase A crafted Rock Ridge ISO image can reference CE continuation blocks outside the mounted ISO volume, creating a narrow local information disclosure path through readlink() when desktop automount or delegated ISO mounting is available. ## 6. Manual review recommendation MANUAL CHECK RECOMMENDED Reason: the score is low, but the issue has a plausible local confidentiality boundary concern involving adjacent block-device data, so it should not be blindly auto-closed without checking deployment exposure such as udisks2 automount and ISO mounting policy. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: isofs: validate Rock Ridge CE continuation extent against volume size Commit: 8356fb821016797f5677cbeee5ddc0d32a95b4be Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8356fb821016797f5677cbeee5ddc0d32a95b4be Commit description: rock_continue() reads rs->cont_extent verbatim from the Rock Ridge CE record and passes it to sb_bread() without checking that the block number is within the mounted ISO 9660 volume. commit e595447 ("[PATCH] rock.c: handle corrupted directories") added cont_offset and cont_size rejection for the CE continuation but did not validate the extent block number itself. commit f54e18f ("isofs: Fix infinite looping over CE entries") later capped the CE chain length at RR_MAX_CE_ENTRIES = 32 but again left the block number unchecked. With a crafted ISO mounted via udisks2 (desktop optical auto-mount) or via CAP_SYS_ADMIN mount, rs->cont_extent can therefore point at an out-of-range block or at blocks belonging to an adjacent filesystem on the same block device. sb_bread() on an out-of-range block returns NULL cleanly via the block layer EIO path, so there is no memory-safety violation. For in-range reads of adjacent- filesystem data, the CE buffer is parsed as Rock Ridge records and only the text of SL sub-records reaches userspace through readlink(), which makes the info-leak channel narrow and difficult to exploit; still, rejecting the malformed CE outright matches the rejection shape already present in the same function for cont_offset and cont_size. Add an ISOFS_SB(sb)->s_nzones bounds check to rock_continue() next to the existing offset/size rejection, printing the same corrupted-directory-entry notice. Fixes: f54e18f ("isofs: Fix infinite looping over CE entries") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-4-7 Signed-off-by: Michael Bommarito Link: https://patch.msgid.link/20260419212155.2169382-2-michael.bommarito@gmail.com Signed-off-by: Jan Kara Signed-off-by: Greg Kroah-Hartman Changed files: fs/isofs/rock.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=8356fb821016797f5677cbeee5ddc0d32a95b4be ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-46303 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46303 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:H/PR:L/UI:N/S:U/C:L/I:N/A:N The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:L 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: 3 Paranoid ActionableScore: 4 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).