{"answers":{"affected":"It affects 1 product.","exploited":"There is no known exploitation of CVE-2026-31561 in the wild and no public exploit code.","fix":"Apply the vendor's patch.","what":"CVE-2026-31561 is a medium-severity vulnerability in Linux kernel, published on 24 Apr 2026. It can only be exploited from the same machine or local network, with no action from the victim."},"fix_prompt":"Check this codebase for CVE-2026-31561 and fix it if it is affected.\n\nWhat it is: CVE-2026-31561 is a medium-severity vulnerability in Linux kernel, published on 24 Apr 2026. It can only be exploited from the same machine or local network, with no action from the victim.\nExploitation: There is no known exploitation of CVE-2026-31561 in the wild and no public exploit code.\n\nAffected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page.\n\nTask:\n1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.\n2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.\n3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.\n4. Run the tests and summarise what changed and why.\n5. If nothing in the project is affected, say so and change nothing.\n\nReference: https://insights.sbomify.com/CVE-2026-31561/ (Markdown: https://insights.sbomify.com/CVE-2026-31561/index.md)","id":"CVE-2026-31561","markdown":"https://insights.sbomify.com/CVE-2026-31561/index.md","name":"CVE-2026-31561","record":{"aliases":["BELL-CVE-2026-31561","DEBIAN-CVE-2026-31561","GHSA-pgvp-p3vq-7q7h","ROOT-OS-DEBIAN-13-CVE-2026-31561","UBUNTU-CVE-2026-31561"],"analysis":{"component_type":"kernel","fix_type":"patch","impacts":["privilege_escalation","denial_of_service"],"network_reachable":"adjacent_or_local","non_default_config":false,"product_category":"Linux kernel","requires_auth":"low_privilege","summary":"Attackers can disable CR4 pinning to bypass security features and escalate privileges or cause system crashes in Linux kernels.","user_interaction":"not_required","vuln_class":"privilege_escalation"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"Linux","cpe":[{"product":"linux_kernel","vendor":"linux"}],"cvss":{"score":5.5,"severity":"medium","source":"nvd","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","version":"3.1"},"cwes":[],"description":"In the Linux kernel, the following vulnerability has been resolved:\n\nx86/cpu: Remove X86_CR4_FRED from the CR4 pinned bits mask\n\nCommit in Fixes added the FRED CR4 bit to the CR4 pinned bits mask so\nthat whenever something else modifies CR4, that bit remains set. Which\nin itself is a perfectly fine idea.\n\nHowever, there's an issue when during boot FRED is initialized: first on\nthe BSP and later on the APs. Thus, there's a window in time when\nexceptions cannot be handled.\n\nThis becomes particularly nasty when running as SEV-{ES,SNP} or TDX\nguests which, when they manage to trigger exceptions during that short\nwindow described above, triple fault due to FRED MSRs not being set up\nyet.\n\nSee Link tag below for a much more detailed explanation of the\nsituation.\n\nSo, as a result, the commit in that Link URL tried to address this\nshortcoming by temporarily disabling CR4 pinning when an AP is not\nonline yet.\n\nHowever, that is a problem in itself because in this case, an attack on\nthe kernel needs to only modify the online bit - a single bit in RW\nmemory - and then disable CR4 pinning and then disable SM*P, leading to\nmore and worse things to happen to the system.\n\nSo, instead, remove the FRED bit from the CR4 pinning mask, thus\nobviating the need to temporarily disable CR4 pinning.\n\nIf someone manages to disable FRED when poking at CR4, then\nidt_invalidate() would make sure the system would crash'n'burn on the\nfirst exception triggered, which is a much better outcome security-wise.","ecosystems":[],"exploits":{"exploitdb":0,"first_seen":null,"github_poc":0,"max_poc_stars":null,"metasploit":0,"nuclei":0,"refs":[],"tier":"none_known"},"has_fix":true,"headline":"x86/cpu: Remove X86_CR4_FRED from the CR4 pinned bits mask","id":"CVE-2026-31561","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":null,"product":"linux:linux_kernel","products":["linux:linux_kernel"],"type":"privilege_escalation","year":"2026"},"n_packages":0,"n_references":4,"next":{"headline":"drm/mediatek: dsi: Store driver data before invoking mipi_dsi_host_register","id":"CVE-2026-31562"},"packages":[],"prev":{"headline":"spi: spi-dw-dma: fix print error log when wait finish transaction","id":"CVE-2026-31560"},"products":["Linux"],"published":"2026-04-24","related":[{"cvss_score":8.8,"headline":"Linux Kernel Out-of-Bounds Write","id":"CVE-2026-53266","kev_date_added":"2026-09-18","published":"2026-06-25"},{"cvss_score":8.8,"headline":"Linux Kernel Improper Input Validation","id":"CVE-2013-6282","kev_date_added":"2022-09-15","published":"2013-11-19"},{"cvss_score":8.4,"headline":"Linux Kernel Heap-Based Buffer Overflow","id":"CVE-2022-0185","kev_date_added":"2024-08-21","published":"2022-02-11"},{"cvss_score":8.4,"headline":"Linux Kernel Privilege Escalation","id":"CVE-2013-2094","kev_date_added":"2022-09-15","published":"2013-05-14"},{"cvss_score":7.8,"headline":"Linux Kernel Unspecified","id":"CVE-2026-53362","kev_date_added":"2026-08-27","published":"2026-07-04"},{"cvss_score":7.8,"headline":"Linux Kernel Missing Initialization of a Variable","id":"CVE-2026-46300","kev_date_added":"2026-10-28","published":"2026-05-23"},{"cvss_score":7.8,"headline":"Linux Kernel Race Condition","id":"CVE-2025-39964","kev_date_added":"2026-09-18","published":"2025-10-13"}],"sources":[{"class":"attribution","licence":"CVE Terms of Use (MITRE)","name":"CVE List","prefix":"CVE"},{"class":"attribution","licence":"US public information, NVD API terms","name":"NVD"},{"class":"attribution","licence":"FIRST CVSS licence","name":"CVSS (FIRST)"}],"ssvc":{"automatable":null,"exploitation":null,"technical_impact":null},"state":"PUBLISHED","updated":"2026-05-11","vendors":["Linux"]},"summary":"Attackers can disable CR4 pinning to bypass security features and escalate privileges or cause system crashes in Linux kernels.","url":"https://insights.sbomify.com/CVE-2026-31561/"}