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CVE-2021-47636 (GCVE-0-2021-47636)

Vulnerability from cvelistv5 – Published: 2025-02-26 01:54 – Updated: 2026-08-05 08:48
VLAI
Title
ubifs: Fix read out-of-bounds in ubifs_wbuf_write_nolock()
Summary
In the Linux kernel, the following vulnerability has been resolved: ubifs: Fix read out-of-bounds in ubifs_wbuf_write_nolock() Function ubifs_wbuf_write_nolock() may access buf out of bounds in following process: ubifs_wbuf_write_nolock(): aligned_len = ALIGN(len, 8); // Assume len = 4089, aligned_len = 4096 if (aligned_len <= wbuf->avail) ... // Not satisfy if (wbuf->used) { ubifs_leb_write() // Fill some data in avail wbuf len -= wbuf->avail; // len is still not 8-bytes aligned aligned_len -= wbuf->avail; } n = aligned_len >> c->max_write_shift; if (n) { n <<= c->max_write_shift; err = ubifs_leb_write(c, wbuf->lnum, buf + written, wbuf->offs, n); // n > len, read out of bounds less than 8(n-len) bytes } , which can be catched by KASAN: ========================================================= BUG: KASAN: slab-out-of-bounds in ecc_sw_hamming_calculate+0x1dc/0x7d0 Read of size 4 at addr ffff888105594ff8 by task kworker/u8:4/128 Workqueue: writeback wb_workfn (flush-ubifs_0_0) Call Trace: kasan_report.cold+0x81/0x165 nand_write_page_swecc+0xa9/0x160 ubifs_leb_write+0xf2/0x1b0 [ubifs] ubifs_wbuf_write_nolock+0x421/0x12c0 [ubifs] write_head+0xdc/0x1c0 [ubifs] ubifs_jnl_write_inode+0x627/0x960 [ubifs] wb_workfn+0x8af/0xb80 Function ubifs_wbuf_write_nolock() accepts that parameter 'len' is not 8 bytes aligned, the 'len' represents the true length of buf (which is allocated in 'ubifs_jnl_xxx', eg. ubifs_jnl_write_inode), so ubifs_wbuf_write_nolock() must handle the length read from 'buf' carefully to write leb safely. Fetch a reproducer in [Link].
Severity
7.1 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2025-10-01 19:50 UTC
CWE
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 1e51764a3c2ac05a23a22b2a95ddee4d9bffb16d , < 5343575aa11c5d7044107d59d43f84aec01312b0 (git)
Affected: 1e51764a3c2ac05a23a22b2a95ddee4d9bffb16d , < b80ccbec0e4804436c382d7dd60e943c386ed83a (git)
Affected: 1e51764a3c2ac05a23a22b2a95ddee4d9bffb16d , < 07a209fadee7b53b46858538e1177597273862e4 (git)
Affected: 1e51764a3c2ac05a23a22b2a95ddee4d9bffb16d , < a7054aaf1909cf40489c0ec1b728fdcf79c751a6 (git)
Affected: 1e51764a3c2ac05a23a22b2a95ddee4d9bffb16d , < e09fa5318d51f522e1af4fbaf8f74999355980c8 (git)
Affected: 1e51764a3c2ac05a23a22b2a95ddee4d9bffb16d , < 3b7fb89135a20587d57f8877c02e25003e9edbdf (git)
Affected: 1e51764a3c2ac05a23a22b2a95ddee4d9bffb16d , < 4f2262a334641e05f645364d5ade1f565c85f20b (git)
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Linux Linux Affected: 2.6.27
Unaffected: 0 , < 2.6.27 (semver)
Unaffected: 4.19.238 , ≤ 4.19.* (semver)
Unaffected: 5.4.189 , ≤ 5.4.* (semver)
Unaffected: 5.10.110 , ≤ 5.10.* (semver)
Unaffected: 5.15.33 , ≤ 5.15.* (semver)
Unaffected: 5.16.19 , ≤ 5.16.* (semver)
Unaffected: 5.17.2 , ≤ 5.17.* (semver)
Unaffected: 5.18 , ≤ * (original_commit_for_fix)
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          "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 \u003c= wbuf-\u003eavail) ... // Not satisfy\n  if (wbuf-\u003eused) {\n    ubifs_leb_write()  // Fill some data in avail wbuf\n    len -= wbuf-\u003eavail;   // len is still not 8-bytes aligned\n    aligned_len -= wbuf-\u003eavail;\n  }\n  n = aligned_len \u003e\u003e c-\u003emax_write_shift;\n  if (n) {\n    n \u003c\u003c= c-\u003emax_write_shift;\n    err = ubifs_leb_write(c, wbuf-\u003elnum, buf + written,\n                          wbuf-\u003eoffs, n);\n    // n \u003e 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 \u0027len\u0027 is not 8\nbytes aligned, the \u0027len\u0027 represents the true length of buf (which is\nallocated in \u0027ubifs_jnl_xxx\u0027, eg. ubifs_jnl_write_inode), so\nubifs_wbuf_write_nolock() must handle the length read from \u0027buf\u0027 carefully\nto write leb safely.\n\nFetch a reproducer in [Link]."
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              "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\u2014all 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."
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        "dateUpdated": "2026-08-05T08:48:42.752Z",
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          "url": "https://git.kernel.org/stable/c/5343575aa11c5d7044107d59d43f84aec01312b0"
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    "assignerShortName": "Linux",
    "cveId": "CVE-2021-47636",
    "datePublished": "2025-02-26T01:54:10.206Z",
    "dateReserved": "2025-02-26T01:48:21.519Z",
    "dateUpdated": "2026-08-05T08:48:42.752Z",
    "state": "PUBLISHED"
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      "cve": "CVE-2021-47636",
      "date": "2026-09-07",
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    "nvd": "{\"cve\":{\"id\":\"CVE-2021-47636\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2025-02-26T06:37:05.377\",\"lastModified\":\"2026-06-17T04:18:12.480\",\"vulnStatus\":\"Modified\",\"cveTags\":[],\"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 \u003c= wbuf-\u003eavail) ... // Not satisfy\\n  if (wbuf-\u003eused) {\\n    ubifs_leb_write()  // Fill some data in avail wbuf\\n    len -= wbuf-\u003eavail;   // len is still not 8-bytes aligned\\n    aligned_len -= wbuf-\u003eavail;\\n  }\\n  n = aligned_len \u003e\u003e c-\u003emax_write_shift;\\n  if (n) {\\n    n \u003c\u003c= c-\u003emax_write_shift;\\n    err = ubifs_leb_write(c, wbuf-\u003elnum, buf + written,\\n                          wbuf-\u003eoffs, n);\\n    // n \u003e 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 \u0027len\u0027 is not 8\\nbytes aligned, the \u0027len\u0027 represents the true length of buf (which is\\nallocated in \u0027ubifs_jnl_xxx\u0027, eg. ubifs_jnl_write_inode), so\\nubifs_wbuf_write_nolock() must handle the length read from \u0027buf\u0027 carefully\\nto write leb safely.\\n\\nFetch a reproducer in [Link].\"},{\"lang\":\"es\",\"value\":\"En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: ubifs: Se corrige la lectura fuera de los l\u00edmites en la funci\u00f3n ubifs_wbuf_write_nolock() ubifs_wbuf_write_nolock() puede acceder a buf fuera de los l\u00edmites en el siguiente proceso: ubifs_wbuf_write_nolock(): classified_len = ALIGN(len, 8); // Supongamos que len = 4089, classified_len = 4096 if (aligned_len \u0026lt;= wbuf-\u0026gt;avail) ... // No satisface if (wbuf-\u0026gt;used) { ubifs_leb_write() // Complete algunos datos en avail wbuf len -= wbuf-\u0026gt;avail; // len a\u00fan no est\u00e1 alineado a 8 bytes classified_len -= wbuf-\u0026gt;avail; } n = classified_len \u0026gt;\u0026gt; c-\u0026gt;max_write_shift; if (n) { n \u0026lt;\u0026lt;= c-\u0026gt;max_write_shift; err = ubifs_leb_write(c, wbuf-\u0026gt;lnum, buf + escrito, wbuf-\u0026gt;offs, n); // n \u0026gt; len, lectura fuera de los l\u00edmites menor a 8(n-len) bytes }, lo cual puede ser detectado por KASAN: =========================================================== ERROR: KASAN: slab fuera de los l\u00edmites en ecc_sw_hamming_calculate+0x1dc/0x7d0 Lectura de tama\u00f1o 4 en la direcci\u00f3n ffff888105594ff8 por la tarea kworker/u8:4/128 Cola de trabajo: escritura diferida wb_workfn (flush-ubifs_0_0) Rastreo de llamadas: kasan_report.cold+0x81/0x165 nand_write_page_swecc+0xa9/0x160 ubifs_leb_write+0xf2/0x1b0 [ubifs] ubifs_wbuf_write_nolock+0x421/0x12c0 [ubifs] write_head+0xdc/0x1c0 [ubifs] ubifs_jnl_write_inode+0x627/0x960 [ubifs] wb_workfn+0x8af/0xb80 La funci\u00f3n ubifs_wbuf_write_nolock() acepta que el par\u00e1metro \u0027len\u0027 no est\u00e9 alineado con 8 bytes, \u0027len\u0027 representa la longitud verdadera de buf (que est\u00e1 asignada en \u0027ubifs_jnl_xxx\u0027, p. ej. ubifs_jnl_write_inode), por lo que ubifs_wbuf_write_nolock() debe manejar la longitud le\u00edda de \u0027buf\u0027 con cuidado para escribir leb de forma segura. Obtenga un reproductor en [Enlace].\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"fs/ubifs/io.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"1e51764a3c2ac05a23a22b2a95ddee4d9bffb16d\",\"lessThan\":\"5343575aa11c5d7044107d59d43f84aec01312b0\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"1e51764a3c2ac05a23a22b2a95ddee4d9bffb16d\",\"lessThan\":\"b80ccbec0e4804436c382d7dd60e943c386ed83a\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"1e51764a3c2ac05a23a22b2a95ddee4d9bffb16d\",\"lessThan\":\"07a209fadee7b53b46858538e1177597273862e4\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"1e51764a3c2ac05a23a22b2a95ddee4d9bffb16d\",\"lessThan\":\"a7054aaf1909cf40489c0ec1b728fdcf79c751a6\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"1e51764a3c2ac05a23a22b2a95ddee4d9bffb16d\",\"lessThan\":\"e09fa5318d51f522e1af4fbaf8f74999355980c8\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"1e51764a3c2ac05a23a22b2a95ddee4d9bffb16d\",\"lessThan\":\"3b7fb89135a20587d57f8877c02e25003e9edbdf\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"1e51764a3c2ac05a23a22b2a95ddee4d9bffb16d\",\"lessThan\":\"4f2262a334641e05f645364d5ade1f565c85f20b\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"fs/ubifs/io.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"2.6.27\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"2.6.27\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"4.19.238\",\"lessThanOrEqual\":\"4.19.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"5.4.189\",\"lessThanOrEqual\":\"5.4.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"5.10.110\",\"lessThanOrEqual\":\"5.10.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"5.15.33\",\"lessThanOrEqual\":\"5.15.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"5.16.19\",\"lessThanOrEqual\":\"5.16.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"5.17.2\",\"lessThanOrEqual\":\"5.17.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"5.18\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"nvd@nist.gov\",\"type\":\"Primary\",\"cvssData\":{\"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\",\"attackVector\":\"LOCAL\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"NONE\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":1.8,\"impactScore\":5.2},{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"type\":\"Secondary\",\"cvssData\":{\"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\",\"attackVector\":\"LOCAL\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"NONE\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":1.8,\"impactScore\":5.2}],\"ssvcV203\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"ssvcData\":{\"timestamp\":\"2025-10-01T19:50:54.449259Z\",\"id\":\"CVE-2021-47636\",\"options\":[{\"exploitation\":\"none\"},{\"automatable\":\"no\"},{\"technicalImpact\":\"partial\"}],\"role\":\"CISA Coordinator\",\"version\":\"2.0.3\"}}]},\"weaknesses\":[{\"source\":\"nvd@nist.gov\",\"type\":\"Primary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-125\"}]},{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"type\":\"Secondary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-125\"}]}],\"configurations\":[{\"nodes\":[{\"operator\":\"OR\",\"negate\":false,\"cpeMatch\":[{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"2.6.27\",\"versionEndExcluding\":\"4.19.238\",\"matchCriteriaId\":\"EF5DCB1F-AE17-4717-80C7-5786A2F74C0C\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"4.20\",\"versionEndExcluding\":\"5.4.189\",\"matchCriteriaId\":\"8CB6E8F5-C2B1-46F3-A807-0F6104AC340F\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"5.5\",\"versionEndExcluding\":\"5.10.110\",\"matchCriteriaId\":\"91D3BFD0-D3F3-4018-957C-96CCBF357D79\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"5.11\",\"versionEndExcluding\":\"5.15.33\",\"matchCriteriaId\":\"27C42AE8-B387-43E2-938A-E1C8B40BE6D5\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"5.16\",\"versionEndExcluding\":\"5.16.19\",\"matchCriteriaId\":\"20C43679-0439-405A-B97F-685BEE50613B\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"5.17\",\"versionEndExcluding\":\"5.17.2\",\"matchCriteriaId\":\"210C679C-CF84-44A3-8939-E629C87E54BF\"}]}]}],\"references\":[{\"url\":\"https://git.kernel.org/stable/c/07a209fadee7b53b46858538e1177597273862e4\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/3b7fb89135a20587d57f8877c02e25003e9edbdf\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/4f2262a334641e05f645364d5ade1f565c85f20b\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/5343575aa11c5d7044107d59d43f84aec01312b0\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/a7054aaf1909cf40489c0ec1b728fdcf79c751a6\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/b80ccbec0e4804436c382d7dd60e943c386ed83a\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/e09fa5318d51f522e1af4fbaf8f74999355980c8\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]}]}}",
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-06-29T22:44:46+00:00",
      "cve": "CVE-2021-47636",
      "id": "CVE-2021-47636",
      "initial_release_date": "2021-01-01T00:00:00+00:00",
      "product_status:known_affected": "14",
      "product_status:known_not_affected": "260",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: ubifs: Fix read out-of-bounds in ubifs_wbuf_write_nolock()",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2021/cve-2021-47636.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-09-04T00:41:52Z",
      "cve": "CVE-2021-47636",
      "id": "CVE-2021-47636",
      "initial_release_date": "2025-02-27T03:14:26Z",
      "product_status:known_affected": "383",
      "product_status:known_not_affected": "352",
      "product_status:recommended": "223",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2021-47636",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2021-47636.json",
      "version": "38"
    },
    "vulnrichment": {
      "containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"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\"}]}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2025-10-01T16:01:21.393Z\"}}], \"cna\": {\"title\": \"ubifs: Fix read out-of-bounds in ubifs_wbuf_write_nolock()\", \"metrics\": [{\"cvssV3_1\": {\"version\": \"3.1\", \"baseScore\": 7.1, \"baseSeverity\": \"HIGH\", \"vectorString\": \"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H\"}, \"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\\u2014all 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\": [{\"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\", \"vendor\": \"Linux\", \"product\": \"Linux\", \"versions\": [{\"status\": \"affected\", \"version\": \"1e51764a3c2ac05a23a22b2a95ddee4d9bffb16d\", \"lessThan\": \"5343575aa11c5d7044107d59d43f84aec01312b0\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"1e51764a3c2ac05a23a22b2a95ddee4d9bffb16d\", \"lessThan\": \"b80ccbec0e4804436c382d7dd60e943c386ed83a\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"1e51764a3c2ac05a23a22b2a95ddee4d9bffb16d\", \"lessThan\": \"07a209fadee7b53b46858538e1177597273862e4\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"1e51764a3c2ac05a23a22b2a95ddee4d9bffb16d\", \"lessThan\": \"a7054aaf1909cf40489c0ec1b728fdcf79c751a6\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"1e51764a3c2ac05a23a22b2a95ddee4d9bffb16d\", \"lessThan\": \"e09fa5318d51f522e1af4fbaf8f74999355980c8\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"1e51764a3c2ac05a23a22b2a95ddee4d9bffb16d\", \"lessThan\": \"3b7fb89135a20587d57f8877c02e25003e9edbdf\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"1e51764a3c2ac05a23a22b2a95ddee4d9bffb16d\", \"lessThan\": \"4f2262a334641e05f645364d5ade1f565c85f20b\", \"versionType\": \"git\"}], \"programFiles\": [\"fs/ubifs/io.c\"], \"defaultStatus\": \"unaffected\"}, {\"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\", \"vendor\": \"Linux\", \"product\": \"Linux\", \"versions\": [{\"status\": \"affected\", \"version\": \"2.6.27\"}, {\"status\": \"unaffected\", \"version\": \"0\", \"lessThan\": \"2.6.27\", \"versionType\": \"semver\"}, {\"status\": \"unaffected\", \"version\": \"4.19.238\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"4.19.*\"}, {\"status\": \"unaffected\", \"version\": \"5.4.189\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.4.*\"}, {\"status\": \"unaffected\", \"version\": \"5.10.110\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.10.*\"}, {\"status\": \"unaffected\", \"version\": \"5.15.33\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.15.*\"}, {\"status\": \"unaffected\", \"version\": \"5.16.19\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.16.*\"}, {\"status\": \"unaffected\", \"version\": \"5.17.2\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.17.*\"}, {\"status\": \"unaffected\", \"version\": \"5.18\", \"versionType\": \"original_commit_for_fix\", \"lessThanOrEqual\": \"*\"}], \"programFiles\": [\"fs/ubifs/io.c\"], \"defaultStatus\": \"affected\"}], \"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\"}], \"x_generator\": {\"engine\": \"bippy-1.2.0\"}, \"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 \u003c= wbuf-\u003eavail) ... // Not satisfy\\n  if (wbuf-\u003eused) {\\n    ubifs_leb_write()  // Fill some data in avail wbuf\\n    len -= wbuf-\u003eavail;   // len is still not 8-bytes aligned\\n    aligned_len -= wbuf-\u003eavail;\\n  }\\n  n = aligned_len \u003e\u003e c-\u003emax_write_shift;\\n  if (n) {\\n    n \u003c\u003c= c-\u003emax_write_shift;\\n    err = ubifs_leb_write(c, wbuf-\u003elnum, buf + written,\\n                          wbuf-\u003eoffs, n);\\n    // n \u003e 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 \u0027len\u0027 is not 8\\nbytes aligned, the \u0027len\u0027 represents the true length of buf (which is\\nallocated in \u0027ubifs_jnl_xxx\u0027, eg. ubifs_jnl_write_inode), so\\nubifs_wbuf_write_nolock() must handle the length read from \u0027buf\u0027 carefully\\nto write leb safely.\\n\\nFetch a reproducer in [Link].\"}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"4.19.238\", \"versionStartIncluding\": \"2.6.27\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.4.189\", \"versionStartIncluding\": \"2.6.27\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.10.110\", \"versionStartIncluding\": \"2.6.27\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.15.33\", \"versionStartIncluding\": \"2.6.27\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.16.19\", \"versionStartIncluding\": \"2.6.27\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.17.2\", \"versionStartIncluding\": \"2.6.27\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.18\", \"versionStartIncluding\": \"2.6.27\"}], \"operator\": \"OR\"}]}], \"providerMetadata\": {\"orgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"shortName\": \"Linux\", \"dateUpdated\": \"2026-08-05T08:48:42.752Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2021-47636\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-08-05T08:48:42.752Z\", \"dateReserved\": \"2025-02-26T01:48:21.519Z\", \"assignerOrgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"datePublished\": \"2025-02-26T01:54:10.206Z\", \"assignerShortName\": \"Linux\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}