{"answers":{"affected":"It affects 1 product.","exploited":"There is no known exploitation of CVE-2026-31519 in the wild and no public exploit code.","fix":"Apply the vendor's patch.","what":"CVE-2026-31519 is a medium-severity vulnerability in Linux kernel, published on 22 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-2026-31519 and fix it if it is affected.\n\nWhat it is: CVE-2026-31519 is a medium-severity vulnerability in Linux kernel, published on 22 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-2026-31519 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-2026-31519/ (Markdown: https://insights.sbomify.com/CVE-2026-31519/index.md)","id":"CVE-2026-31519","markdown":"https://insights.sbomify.com/CVE-2026-31519/index.md","name":"CVE-2026-31519","record":{"aliases":["AZL-83294","BELL-CVE-2026-31519","DEBIAN-CVE-2026-31519","GHSA-p3jm-9f4h-xp4f","ROOT-OS-DEBIAN-11-CVE-2026-31519","ROOT-OS-DEBIAN-12-CVE-2026-31519","ROOT-OS-DEBIAN-13-CVE-2026-31519","ROOT-OS-UBUNTU-2204-CVE-2026-31519","ROOT-OS-UBUNTU-2404-CVE-2026-31519","UBUNTU-CVE-2026-31519"],"analysis":{"component_type":"kernel","fix_type":"patch","impacts":["denial_of_service"],"network_reachable":"adjacent_or_local","non_default_config":false,"product_category":"Linux kernel filesystem","requires_auth":"low_privilege","summary":"A null pointer dereference in the Btrfs filesystem during subvolume creation can cause filesystem errors and denial of service.","user_interaction":"not_required","vuln_class":"null_dereference"},"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":[{"id":"CWE-476","name":"NULL Pointer Dereference"}],"description":"In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: set BTRFS_ROOT_ORPHAN_CLEANUP during subvol create\n\nWe have recently observed a number of subvolumes with broken dentries.\nls-ing the parent dir looks like:\n\ndrwxrwxrwt 1 root root 16 Jan 23 16:49 .\ndrwxr-xr-x 1 root root 24 Jan 23 16:48 ..\nd????????? ? ?    ?     ?            ? broken_subvol\n\nand similarly stat-ing the file fails.\n\nIn this state, deleting the subvol fails with ENOENT, but attempting to\ncreate a new file or subvol over it errors out with EEXIST and even\naborts the fs. Which leaves us a bit stuck.\n\ndmesg contains a single notable error message reading:\n\"could not do orphan cleanup -2\"\n\n2 is ENOENT and the error comes from the failure handling path of\nbtrfs_orphan_cleanup(), with the stack leading back up to\nbtrfs_lookup().\n\nbtrfs_lookup\nbtrfs_lookup_dentry\nbtrfs_orphan_cleanup // prints that message and returns -ENOENT\n\nAfter some detailed inspection of the internal state, it became clear\nthat:\n- there are no orphan items for the subvol\n- the subvol is otherwise healthy looking, it is not half-deleted or\n  anything, there is no drop progress, etc.\n- the subvol was created a while ago and does the meaningful first\n  btrfs_orphan_cleanup() call that sets BTRFS_ROOT_ORPHAN_CLEANUP much\n  later.\n- after btrfs_orphan_cleanup() fails, btrfs_lookup_dentry() returns -ENOENT,\n  which results in a negative dentry for the subvolume via\n  d_splice_alias(NULL, dentry), leading to the observed behavior. The\n  bug can be mitigated by dropping the dentry cache, at which point we\n  can successfully delete the subvolume if we want.\n\ni.e.,\nbtrfs_lookup()\n  btrfs_lookup_dentry()\n    if (!sb_rdonly(inode-\u003evfs_inode)-\u003evfs_inode)\n    btrfs_orphan_cleanup(sub_root)\n      test_and_set_bit(BTRFS_ROOT_ORPHAN_CLEANUP)\n      btrfs_search_slot() // finds orphan item for inode N\n      ...\n      prints \"could not do orphan cleanup -2\"\n  if (inode == ERR_PTR(-ENOENT))\n    inode = NULL;\n  return d_splice_alias(NULL, dentry) // NEGATIVE DENTRY for valid subvolume\n\nbtrfs_orphan_cleanup() does test_and_set_bit(BTRFS_ROOT_ORPHAN_CLEANUP)\non the root when it runs, so it cannot run more than once on a given\nroot, so something else must run concurrently. However, the obvious\nroutes to deleting an orphan when nlinks goes to 0 should not be able to\nrun without first doing a lookup into the subvolume, which should run\nbtrfs_orphan_cleanup() and set the bit.\n\nThe final important observation is that create_subvol() calls\nd_instantiate_new() but does not set BTRFS_ROOT_ORPHAN_CLEANUP, so if\nthe dentry cache gets dropped, the next lookup into the subvolume will\nmake a real call into btrfs_orphan_cleanup() for the first time. This\nopens up the possibility of concurrently deleting the inode/orphan items\nbut most typical evict() paths will be holding a reference on the parent\ndentry (child dentry holds parent-\u003ed_lockref.count via dget in\nd_alloc(), released in __dentry_kill()) and prevent the parent from\nbeing removed from the dentry cache.\n\nThe one exception is delayed iputs. Ordered extent creation calls\nigrab() on the inode. If the file is unlinked and closed while those\nrefs are held, iput() in __dentry_kill() decrements i_count but does\nnot trigger eviction (i_count \u003e 0). The child dentry is freed and the\nsubvol dentry's d_lockref.count drops to 0, making it evictable while\nthe inode is still alive.\n\nSince there are two races (the race between writeback and unlink and\nthe race between lookup and delayed iputs), and there are too many moving\nparts, the following three diagrams show the complete picture.\n(Only the second and third are races)\n\nPhase 1:\nCreate Subvol in dentry cache without BTRFS_ROOT_ORPHAN_CLEANUP set\n\nbtrfs_mksubvol()\n  lookup_one_len()\n    __lookup_slow()\n      d_alloc_parallel()\n        __d_alloc() // d_lockref.count = 1\n  create_subvol(dentry)\n    // doesn't touch the bit..\n    d_instantiate_new(dentry, inode) // dentry in cache with d_lockref.c\n---truncated---","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":"btrfs: set BTRFS_ROOT_ORPHAN_CLEANUP during subvol create","id":"CVE-2026-31519","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":null,"product":"linux:linux_kernel","products":["linux:linux_kernel"],"type":"null_dereference","year":"2026"},"n_packages":0,"n_references":6,"next":{"headline":"HID: apple: avoid memory leak in apple_report_fixup()","id":"CVE-2026-31520"},"packages":[],"prev":{"headline":"esp: fix skb leak with espintcp and async crypto","id":"CVE-2026-31518"},"products":["Linux"],"published":"2026-04-22","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":"CWE Terms of Use","name":"CWE (MITRE)"},{"class":"attribution","licence":"FIRST CVSS licence","name":"CVSS (FIRST)"}],"ssvc":{"automatable":null,"exploitation":null,"technical_impact":null},"state":"PUBLISHED","updated":"2026-05-23","vendors":["Linux"]},"summary":"A null pointer dereference in the Btrfs filesystem during subvolume creation can cause filesystem errors and denial of service.","url":"https://insights.sbomify.com/CVE-2026-31519/"}