{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2021-47636", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2025-02-26T01:48:21.519Z", "datePublished": "2025-02-26T01:54:10.206Z", "dateUpdated": "2026-08-05T08:48:42.752Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T08:48:42.752Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nubifs: Fix read out-of-bounds in ubifs_wbuf_write_nolock()\n\nFunction ubifs_wbuf_write_nolock() may access buf out of bounds in\nfollowing process:\n\nubifs_wbuf_write_nolock():\n aligned_len = ALIGN(len, 8); // Assume len = 4089, aligned_len = 4096\n if (aligned_len <= wbuf->avail) ... // Not satisfy\n if (wbuf->used) {\n ubifs_leb_write() // Fill some data in avail wbuf\n len -= wbuf->avail; // len is still not 8-bytes aligned\n aligned_len -= wbuf->avail;\n }\n n = aligned_len >> c->max_write_shift;\n if (n) {\n n <<= c->max_write_shift;\n err = ubifs_leb_write(c, wbuf->lnum, buf + written,\n wbuf->offs, n);\n // n > len, read out of bounds less than 8(n-len) bytes\n }\n\n, which can be catched by KASAN:\n =========================================================\n BUG: KASAN: slab-out-of-bounds in ecc_sw_hamming_calculate+0x1dc/0x7d0\n Read of size 4 at addr ffff888105594ff8 by task kworker/u8:4/128\n Workqueue: writeback wb_workfn (flush-ubifs_0_0)\n Call Trace:\n kasan_report.cold+0x81/0x165\n nand_write_page_swecc+0xa9/0x160\n ubifs_leb_write+0xf2/0x1b0 [ubifs]\n ubifs_wbuf_write_nolock+0x421/0x12c0 [ubifs]\n write_head+0xdc/0x1c0 [ubifs]\n ubifs_jnl_write_inode+0x627/0x960 [ubifs]\n wb_workfn+0x8af/0xb80\n\nFunction ubifs_wbuf_write_nolock() accepts that parameter 'len' is not 8\nbytes aligned, the 'len' represents the true length of buf (which is\nallocated in 'ubifs_jnl_xxx', eg. ubifs_jnl_write_inode), so\nubifs_wbuf_write_nolock() must handle the length read from 'buf' carefully\nto write leb safely.\n\nFetch a reproducer in [Link]." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H", "baseScore": 7.1, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - The bug is in UBIFS local journal writeback (ubifs_wbuf_write_nolock), reached via VFS operations such as creating a long symlink and forcing inode writeback on an already-mounted flash filesystem; it is not in a network-facing protocol stack.\nAC:L - A public reproducer reliably triggers the path by filling the journal write-buffer (deep mkdir tree), creating a non-8-byte-aligned symlink, and waiting for writeback—all conditions the attacker controls.\nPR:L - On typical UBIFS deployments (embedded/Android system or data volumes already mounted), an unprivileged user with write permission can create symlinks/directories and dirty inodes to reach the vulnerable writeback path without needing CAP_SYS_ADMIN.\nUI:N - No victim action is required once UBIFS is mounted as system storage; the attacker alone performs the filesystem operations that dirty the inode and trigger writeback.\nS:U - Impact is confined to the local kernel/OS security authority (heap disclosure and possible oops); there is no VM escape, IOMMU bypass, or other cross-boundary effect.\nC:H - The bug is a slab out-of-bounds read of adjacent kernel heap that is then written to flash via ubifs_leb_write, so leaked kernel memory can be exposed; choosing the higher severity for this memory disclosure.\nI:N - This is a read-only out-of-bounds access with no attacker-controlled write primitive, type confusion, or other integrity corruption of kernel state.\nA:H - Reading past a kmalloc object can fault into unmapped/adjacent memory and cause a kernel oops, and the KASAN report confirms a hard out-of-bounds access on the writeback path." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/ubifs/io.c" ], "versions": [ { "version": "1e51764a3c2ac05a23a22b2a95ddee4d9bffb16d", "lessThan": "5343575aa11c5d7044107d59d43f84aec01312b0", "status": "affected", "versionType": "git" }, { "version": "1e51764a3c2ac05a23a22b2a95ddee4d9bffb16d", "lessThan": "b80ccbec0e4804436c382d7dd60e943c386ed83a", "status": "affected", "versionType": "git" }, { "version": "1e51764a3c2ac05a23a22b2a95ddee4d9bffb16d", "lessThan": "07a209fadee7b53b46858538e1177597273862e4", "status": "affected", "versionType": "git" }, { "version": "1e51764a3c2ac05a23a22b2a95ddee4d9bffb16d", "lessThan": "a7054aaf1909cf40489c0ec1b728fdcf79c751a6", "status": "affected", "versionType": "git" }, { "version": "1e51764a3c2ac05a23a22b2a95ddee4d9bffb16d", "lessThan": "e09fa5318d51f522e1af4fbaf8f74999355980c8", "status": "affected", "versionType": "git" }, { "version": "1e51764a3c2ac05a23a22b2a95ddee4d9bffb16d", "lessThan": "3b7fb89135a20587d57f8877c02e25003e9edbdf", "status": "affected", "versionType": "git" }, { "version": "1e51764a3c2ac05a23a22b2a95ddee4d9bffb16d", "lessThan": "4f2262a334641e05f645364d5ade1f565c85f20b", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/ubifs/io.c" ], "versions": [ { "version": "2.6.27", "status": "affected" }, { "version": "0", "lessThan": "2.6.27", "status": "unaffected", "versionType": "semver" }, { "version": "4.19.238", "lessThanOrEqual": "4.19.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.4.189", "lessThanOrEqual": "5.4.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.110", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.33", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.16.19", "lessThanOrEqual": "5.16.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.17.2", "lessThanOrEqual": "5.17.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.18", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.27", "versionEndExcluding": "4.19.238" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.27", "versionEndExcluding": "5.4.189" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.27", "versionEndExcluding": "5.10.110" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.27", "versionEndExcluding": "5.15.33" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.27", "versionEndExcluding": "5.16.19" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.27", "versionEndExcluding": "5.17.2" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.27", "versionEndExcluding": "5.18" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/5343575aa11c5d7044107d59d43f84aec01312b0" }, { "url": "https://git.kernel.org/stable/c/b80ccbec0e4804436c382d7dd60e943c386ed83a" }, { "url": "https://git.kernel.org/stable/c/07a209fadee7b53b46858538e1177597273862e4" }, { "url": "https://git.kernel.org/stable/c/a7054aaf1909cf40489c0ec1b728fdcf79c751a6" }, { "url": "https://git.kernel.org/stable/c/e09fa5318d51f522e1af4fbaf8f74999355980c8" }, { "url": "https://git.kernel.org/stable/c/3b7fb89135a20587d57f8877c02e25003e9edbdf" }, { "url": "https://git.kernel.org/stable/c/4f2262a334641e05f645364d5ade1f565c85f20b" } ], "title": "ubifs: Fix read out-of-bounds in ubifs_wbuf_write_nolock()", "x_generator": { "engine": "bippy-1.2.0" } }, "adp": [ { "metrics": [ { "cvssV3_1": { "scope": "UNCHANGED", "version": "3.1", "baseScore": 7.1, "attackVector": "LOCAL", "baseSeverity": "HIGH", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H", "integrityImpact": "NONE", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "HIGH", "privilegesRequired": "LOW", "confidentialityImpact": "HIGH" } }, { "other": { "type": "ssvc", "content": { "id": "CVE-2021-47636", "role": "CISA Coordinator", "options": [ { "Exploitation": "none" }, { "Automatable": "no" }, { "Technical Impact": "partial" } ], "version": "2.0.3", "timestamp": "2025-10-01T19:50:54.449259Z" } } } ], "problemTypes": [ { "descriptions": [ { "lang": "en", "type": "CWE", "cweId": "CWE-125", "description": "CWE-125 Out-of-bounds Read" } ] } ], "title": "CISA ADP Vulnrichment", "providerMetadata": { "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2025-10-01T19:57:08.785Z" } } ] } }