{"cve":"CVE-2025-38691","nvd":{"published":"2025-09-04T16:15:37.297","modified":"2026-10-19T21:10:00.160","status":"Modified","description":"In the Linux kernel, the following vulnerability has been resolved:\n\npNFS: Fix uninited ptr deref in block/scsi layout\n\nThe error occurs on the third attempt to encode extents. When function\next_tree_prepare_commit() reallocates a larger buffer to retry encoding\nextents, the \"layoutupdate_pages\" page array is initialized only after the\nretry loop. But ext_tree_free_commitdata() is called on every iteration\nand tries to put pages in the array, thus dereferencing uninitialized\npointers.\n\nAn additional problem is that there is no limit on the maximum possible\nbuffer_size. When there are too many extents, the client may create a\nlayoutcommit that is larger than the maximum possible RPC size accepted\nby the server.\n\nDuring testing, we observed two typical scenarios. First, one memory page\nfor extents is enough when we work with small files, append data to the\nend of the file, or preallocate extents before writing. But when we fill\na new large file without preallocating, the number of extents can be huge,\nand counting the number of written extents in ext_tree_encode_commit()\ndoes not help much. Since this number increases even more between\nunlocking and locking of ext_tree, the reallocated buffer may not be\nlarge enough again and again.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","score":5.5},"cwes":["CWE-908"],"references":["https://git.kernel.org/stable/c/24334f3cf8a294f253071b5bf22d754dbb6d0f2d","https://git.kernel.org/stable/c/2896f101110076ac6bf99d7aaf463d61e26f89dd","https://git.kernel.org/stable/c/37c3443a2685528f972d910a6fb87716b96fef46","https://git.kernel.org/stable/c/4f783333cbfa2ee7d4aa8e47f6bd1b3f77534fcf","https://git.kernel.org/stable/c/579b85f893d9885162e1cabf99a4a088916e143e"],"products":["debian:debian_linux","linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-21T03:43:09.190223697+00:00"},"epss":{"cve":"CVE-2025-38691","score":0.00183,"percentile":0.07774,"date":"2026-10-26"},"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."]}