{"cve":"CVE-2026-31702","nvd":{"published":"2026-05-01T14:16:20.140","modified":"2026-06-17T10:34:16.310","status":"Modified","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nf2fs: fix use-after-free of sbi in f2fs_compress_write_end_io()\n\nIn f2fs_compress_write_end_io(), dec_page_count(sbi, type) can bring\nthe F2FS_WB_CP_DATA counter to zero, unblocking\nf2fs_wait_on_all_pages() in f2fs_put_super() on a concurrent unmount\nCPU. The unmount path then proceeds to call\nf2fs_destroy_page_array_cache(sbi), which destroys\nsbi->page_array_slab via kmem_cache_destroy(), and eventually\nkfree(sbi). Meanwhile, the bio completion callback is still executing:\nwhen it reaches page_array_free(sbi, ...), it dereferences\nsbi->page_array_slab — a destroyed slab cache — to call\nkmem_cache_free(), causing a use-after-free.\n\nThis is the same class of bug as CVE-2026-23234 (which fixed the\nequivalent race in f2fs_write_end_io() in data.c), but in the\ncompressed writeback completion path that was not covered by that fix.\n\nFix this by moving dec_page_count() to after page_array_free(), so\nthat all sbi accesses complete before the counter decrement that can\nunblock unmount. For non-last folios (where atomic_dec_return on\ncic->pending_pages is nonzero), dec_page_count is called immediately\nbefore returning — page_array_free is not reached on this path, so\nthere is no post-decrement sbi access. For the last folio,\npage_array_free runs while the F2FS_WB_CP_DATA counter is still\nnonzero (this folio has not yet decremented it), keeping sbi alive,\nand dec_page_count runs as the final operation.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","score":7.8},"cwes":["CWE-416"],"references":["https://git.kernel.org/stable/c/2c97dcb6147c8f7f25c629b93be1e69617de5d4a","https://git.kernel.org/stable/c/39d4ee19c1e7d753dd655aebee632271b171f43a","https://git.kernel.org/stable/c/57bc678f36ac03281e877c6b84877b43f964143f","https://git.kernel.org/stable/c/c76cf339b87975ae5b2c06d2d774d5667d25a12a","https://git.kernel.org/stable/c/ef57cd3329b40c739b9a2e1a8a21ecc4171c6280"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T22:33:09.003606135+00:00"},"epss":{"cve":"CVE-2026-31702","score":0.00119,"percentile":0.01769,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}