{"api_version":"1","generated_at":"2026-07-20T23:55:19+00:00","cve":"CVE-2026-63949","urls":{"html":"https://cve.report/CVE-2026-63949","api":"https://cve.report/api/cve/CVE-2026-63949.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-63949","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-63949"},"summary":{"title":"auxdisplay: line-display: fix OOB read on zero-length message_store()","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nauxdisplay: line-display: fix OOB read on zero-length message_store()\n\nlinedisp_display() unconditionally reads msg[count - 1] before\nchecking whether count is zero, so a write of zero bytes to the\nmessage sysfs attribute hits msg[-1]:\n\n\twrite(fd, \"\", 0);\n\n\t-> message_store(..., buf, count=0)\n\t   -> linedisp_display(linedisp, buf, count=0)\n\t      -> msg[count - 1] == '\\n'  ; OOB read\n\nThe kernfs write buffer for that store is a 1-byte allocation\n(kernfs_fop_write_iter() does kmalloc(len + 1) with len == 0),\nso msg[-1] is a 1-byte read before the slab object. On a\nKASAN-enabled kernel this trips an out-of-bounds report and\npanics; on stock kernels it silently reads adjacent slab data\nand, if that byte happens to be '\\n', the following count--\nwraps ssize_t 0 to -1 and is then passed to kmemdup_nul().\n\nlinedisp_display() is reached from the message_store() sysfs\ncallback (drivers/auxdisplay/line-display.c message attribute,\nmode 0644) and from the in-tree initial-message setup with\ncount == -1, so the OOB path is only userspace-triggerable via\nzero-byte writes; vfs_write() does not short-circuit on\ncount == 0 and kernfs_fop_write_iter() dispatches the store\ncallback regardless.\n\nGuard the trailing-newline trim with a count check. The\nexisting if (!count) block then takes the clear-display path\nunchanged.\n\nAffects every auxdisplay driver that registers via\nlinedisp_register() / linedisp_attach(): ht16k33, max6959,\nimg-ascii-lcd, seg-led-gpio.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-07-19 16:17:13","updated_at":"2026-07-19 16:17:13"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/197476b126010bac1b3199833c6966cd6f54c2a9","name":"https://git.kernel.org/stable/c/197476b126010bac1b3199833c6966cd6f54c2a9","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/6ad4f75ef9f3372fce8cad494e789ac6a5507bef","name":"https://git.kernel.org/stable/c/6ad4f75ef9f3372fce8cad494e789ac6a5507bef","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/a7511dcd9dd4bc55d123f9b800c8a4ed2662e5c6","name":"https://git.kernel.org/stable/c/a7511dcd9dd4bc55d123f9b800c8a4ed2662e5c6","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/ca5b0781946d5083ceafa752141f47f085853620","name":"https://git.kernel.org/stable/c/ca5b0781946d5083ceafa752141f47f085853620","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/8776032fe989a9b5fc77f2de5e03e4adb44c630e","name":"https://git.kernel.org/stable/c/8776032fe989a9b5fc77f2de5e03e4adb44c630e","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/3859960daeb9b7b39b9847b5b0113bc6081eb735","name":"https://git.kernel.org/stable/c/3859960daeb9b7b39b9847b5b0113bc6081eb735","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-63949","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-63949","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 7e76aece6f036cb7ada4858d6aa73825bfe22983 ca5b0781946d5083ceafa752141f47f085853620 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 7e76aece6f036cb7ada4858d6aa73825bfe22983 8776032fe989a9b5fc77f2de5e03e4adb44c630e git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 7e76aece6f036cb7ada4858d6aa73825bfe22983 3859960daeb9b7b39b9847b5b0113bc6081eb735 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 7e76aece6f036cb7ada4858d6aa73825bfe22983 197476b126010bac1b3199833c6966cd6f54c2a9 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 7e76aece6f036cb7ada4858d6aa73825bfe22983 6ad4f75ef9f3372fce8cad494e789ac6a5507bef git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 7e76aece6f036cb7ada4858d6aa73825bfe22983 a7511dcd9dd4bc55d123f9b800c8a4ed2662e5c6 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 5.16","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 5.16 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.1.176 6.1.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.6.143 6.6.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.12.93 6.12.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.35 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.0.12 7.0.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.1 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["drivers/auxdisplay/line-display.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"ca5b0781946d5083ceafa752141f47f085853620","status":"affected","version":"7e76aece6f036cb7ada4858d6aa73825bfe22983","versionType":"git"},{"lessThan":"8776032fe989a9b5fc77f2de5e03e4adb44c630e","status":"affected","version":"7e76aece6f036cb7ada4858d6aa73825bfe22983","versionType":"git"},{"lessThan":"3859960daeb9b7b39b9847b5b0113bc6081eb735","status":"affected","version":"7e76aece6f036cb7ada4858d6aa73825bfe22983","versionType":"git"},{"lessThan":"197476b126010bac1b3199833c6966cd6f54c2a9","status":"affected","version":"7e76aece6f036cb7ada4858d6aa73825bfe22983","versionType":"git"},{"lessThan":"6ad4f75ef9f3372fce8cad494e789ac6a5507bef","status":"affected","version":"7e76aece6f036cb7ada4858d6aa73825bfe22983","versionType":"git"},{"lessThan":"a7511dcd9dd4bc55d123f9b800c8a4ed2662e5c6","status":"affected","version":"7e76aece6f036cb7ada4858d6aa73825bfe22983","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["drivers/auxdisplay/line-display.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"5.16"},{"lessThan":"5.16","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"6.1.*","status":"unaffected","version":"6.1.176","versionType":"semver"},{"lessThanOrEqual":"6.6.*","status":"unaffected","version":"6.6.143","versionType":"semver"},{"lessThanOrEqual":"6.12.*","status":"unaffected","version":"6.12.93","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.35","versionType":"semver"},{"lessThanOrEqual":"7.0.*","status":"unaffected","version":"7.0.12","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.1","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.1.176","versionStartIncluding":"5.16","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.6.143","versionStartIncluding":"5.16","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.12.93","versionStartIncluding":"5.16","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.35","versionStartIncluding":"5.16","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.0.12","versionStartIncluding":"5.16","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.1","versionStartIncluding":"5.16","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nauxdisplay: line-display: fix OOB read on zero-length message_store()\n\nlinedisp_display() unconditionally reads msg[count - 1] before\nchecking whether count is zero, so a write of zero bytes to the\nmessage sysfs attribute hits msg[-1]:\n\n\twrite(fd, \"\", 0);\n\n\t-> message_store(..., buf, count=0)\n\t   -> linedisp_display(linedisp, buf, count=0)\n\t      -> msg[count - 1] == '\\n'  ; OOB read\n\nThe kernfs write buffer for that store is a 1-byte allocation\n(kernfs_fop_write_iter() does kmalloc(len + 1) with len == 0),\nso msg[-1] is a 1-byte read before the slab object. On a\nKASAN-enabled kernel this trips an out-of-bounds report and\npanics; on stock kernels it silently reads adjacent slab data\nand, if that byte happens to be '\\n', the following count--\nwraps ssize_t 0 to -1 and is then passed to kmemdup_nul().\n\nlinedisp_display() is reached from the message_store() sysfs\ncallback (drivers/auxdisplay/line-display.c message attribute,\nmode 0644) and from the in-tree initial-message setup with\ncount == -1, so the OOB path is only userspace-triggerable via\nzero-byte writes; vfs_write() does not short-circuit on\ncount == 0 and kernfs_fop_write_iter() dispatches the store\ncallback regardless.\n\nGuard the trailing-newline trim with a count check. The\nexisting if (!count) block then takes the clear-display path\nunchanged.\n\nAffects every auxdisplay driver that registers via\nlinedisp_register() / linedisp_attach(): ht16k33, max6959,\nimg-ascii-lcd, seg-led-gpio."}],"providerMetadata":{"dateUpdated":"2026-07-19T14:55:42.679Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/ca5b0781946d5083ceafa752141f47f085853620"},{"url":"https://git.kernel.org/stable/c/8776032fe989a9b5fc77f2de5e03e4adb44c630e"},{"url":"https://git.kernel.org/stable/c/3859960daeb9b7b39b9847b5b0113bc6081eb735"},{"url":"https://git.kernel.org/stable/c/197476b126010bac1b3199833c6966cd6f54c2a9"},{"url":"https://git.kernel.org/stable/c/6ad4f75ef9f3372fce8cad494e789ac6a5507bef"},{"url":"https://git.kernel.org/stable/c/a7511dcd9dd4bc55d123f9b800c8a4ed2662e5c6"}],"title":"auxdisplay: line-display: fix OOB read on zero-length message_store()","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-63949","datePublished":"2026-07-19T14:55:42.679Z","dateReserved":"2026-07-19T07:54:57.023Z","dateUpdated":"2026-07-19T14:55:42.679Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-07-19 16:17:13","lastModifiedDate":"2026-07-19 16:17:13","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"63949","Ordinal":"1","Title":"auxdisplay: line-display: fix OOB read on zero-length message_st","CVE":"CVE-2026-63949","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"63949","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\nauxdisplay: line-display: fix OOB read on zero-length message_store()\n\nlinedisp_display() unconditionally reads msg[count - 1] before\nchecking whether count is zero, so a write of zero bytes to the\nmessage sysfs attribute hits msg[-1]:\n\n\twrite(fd, \"\", 0);\n\n\t-> message_store(..., buf, count=0)\n\t   -> linedisp_display(linedisp, buf, count=0)\n\t      -> msg[count - 1] == '\\n'  ; OOB read\n\nThe kernfs write buffer for that store is a 1-byte allocation\n(kernfs_fop_write_iter() does kmalloc(len + 1) with len == 0),\nso msg[-1] is a 1-byte read before the slab object. On a\nKASAN-enabled kernel this trips an out-of-bounds report and\npanics; on stock kernels it silently reads adjacent slab data\nand, if that byte happens to be '\\n', the following count--\nwraps ssize_t 0 to -1 and is then passed to kmemdup_nul().\n\nlinedisp_display() is reached from the message_store() sysfs\ncallback (drivers/auxdisplay/line-display.c message attribute,\nmode 0644) and from the in-tree initial-message setup with\ncount == -1, so the OOB path is only userspace-triggerable via\nzero-byte writes; vfs_write() does not short-circuit on\ncount == 0 and kernfs_fop_write_iter() dispatches the store\ncallback regardless.\n\nGuard the trailing-newline trim with a count check. The\nexisting if (!count) block then takes the clear-display path\nunchanged.\n\nAffects every auxdisplay driver that registers via\nlinedisp_register() / linedisp_attach(): ht16k33, max6959,\nimg-ascii-lcd, seg-led-gpio.","Type":"Description","Title":"auxdisplay: line-display: fix OOB read on zero-length message_st"}]}}}