{"answers":{"affected":"","exploited":"There is no known exploitation of CVE-2026-63811 in the wild and no public exploit code.","fix":"Apply the vendor's patch.","what":"CVE-2026-63811 is a vulnerability in Linux, published on 19 Jul 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-2026-63811 and fix it if it is affected.\n\nWhat it is: CVE-2026-63811 is a vulnerability in Linux, published on 19 Jul 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-2026-63811 in the wild and no public exploit code.\n\nAffected product: Linux. 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-2026-63811/ (Markdown: https://insights.sbomify.com/CVE-2026-63811/index.md)","id":"CVE-2026-63811","markdown":"https://insights.sbomify.com/CVE-2026-63811/index.md","name":"CVE-2026-63811","record":{"aliases":["BELL-CVE-2026-63811","DEBIAN-CVE-2026-63811","GHSA-wqxg-ff3c-39jf","UBUNTU-CVE-2026-63811"],"analysis":{"component_type":"kernel","fix_type":"patch","impacts":["denial_of_service"],"network_reachable":"adjacent_or_local","non_default_config":true,"product_category":"Linux kernel filesystem","requires_auth":"low_privilege","summary":"A null pointer dereference in the Linux kernel f2fs filesystem allows local attackers to cause a system crash during atomic writes with encryption.","user_interaction":"not_required","vuln_class":"null_dereference"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"Linux","cpe":[],"cvss":{"score":null,"severity":null,"source":null,"vector":null,"version":null},"cwes":[],"description":"In the Linux kernel, the following vulnerability has been resolved:\n\nf2fs: read COW data with the original inode during atomic write\n\nWhen updating an atomic-write file, f2fs_write_begin() may read the\npreviously written data back from the COW inode:\nprepare_atomic_write_begin() locates the block in the COW inode and sets\nuse_cow, and the read bio is then built with the COW inode:\n\n\tf2fs_submit_page_read(use_cow ? F2FS_I(inode)-\u003ecow_inode : inode,\n\t\t\t      ...);\n\nand f2fs_grab_read_bio() decides whether to schedule fs-layer decryption\n(STEP_DECRYPT) for the bio based on that inode via\nfscrypt_inode_uses_fs_layer_crypto().\n\nHowever, the folio being filled belongs to the original inode\n(folio-\u003emapping-\u003ehost == inode), and the data stored in the COW block was\nencrypted (or left as plaintext) using the original inode's context, not\nthe COW inode's -- see f2fs_encrypt_one_page(), which keys off\nfio-\u003epage-\u003emapping-\u003ehost.  fscrypt_decrypt_pagecache_blocks() likewise\noperates on folio-\u003emapping-\u003ehost.\n\nThe COW inode is created as a tmpfile in the parent directory and inherits\nits encryption policy from there.  With test_dummy_encryption the newly\ncreated COW inode gets the dummy policy and becomes encrypted, while a\npre-existing regular file -- created before the policy applied, e.g.\nalready present in the on-disk image -- stays unencrypted.  The read\npath then sets STEP_DECRYPT based on the encrypted COW inode and calls\nfscrypt_decrypt_pagecache_blocks() on a folio whose host (the unencrypted\noriginal inode) has a NULL -\u003ei_crypt_info, dereferencing it:\n\n  Oops: general protection fault, probably for non-canonical address ...\n  KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]\n  RIP: 0010:fscrypt_decrypt_pagecache_blocks+0xa0/0x310\n  Workqueue: f2fs_post_read_wq f2fs_post_read_work\n  Call Trace:\n   fscrypt_decrypt_bio+0x1eb/0x340\n   f2fs_post_read_work+0xba/0x140\n   process_one_work+0x91c/0x1a40\n   worker_thread+0x677/0xe90\n   kthread+0x2bc/0x3a0\n\nThe COW inode is only needed to locate the on-disk block, and that block\naddress is already resolved into @blkaddr by prepare_atomic_write_begin()\nvia __find_data_block(cow_inode, ...); f2fs_submit_page_read() then reads\nfrom that physical @blkaddr directly, so the inode argument only selects\nthe post-read crypto context, not which block is fetched.  Reading with\n@inode therefore returns the same (latest, not-yet-committed) COW data,\nwhile making both the fs-layer decryption decision and the inline crypto\npath use the correct (original inode's) key.\n\nWith the COW inode no longer used at the read site, the use_cow flag has no\nremaining consumer; drop it from f2fs_write_begin() and\nprepare_atomic_write_begin().","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":"f2fs: read COW data with the original inode during atomic write","id":"CVE-2026-63811","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":null,"product":null,"products":[],"type":"null_dereference","year":"2026"},"n_packages":0,"n_references":5,"next":{"headline":"f2fs: fix incorrect FI_NO_EXTENT handling in __destroy_extent_node()","id":"CVE-2026-63812"},"packages":[],"prev":{"headline":"block: Avoid mounting the bdev pseudo-filesystem in userspace","id":"CVE-2026-63810"},"products":["Linux"],"published":"2026-07-19","related":[],"sources":[{"class":"attribution","licence":"CVE Terms of Use (MITRE)","name":"CVE List","prefix":"CVE"}],"ssvc":{"automatable":null,"exploitation":null,"technical_impact":null},"state":"PUBLISHED","updated":"2026-10-21","vendors":["Linux"]},"summary":"A null pointer dereference in the Linux kernel f2fs filesystem allows local attackers to cause a system crash during atomic writes with encryption.","url":"https://insights.sbomify.com/CVE-2026-63811/"}