{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-23225", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-01-13T15:37:45.987Z", "datePublished": "2026-02-18T14:53:28.387Z", "dateUpdated": "2026-08-05T12:20:43.404Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T12:20:43.404Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsched/mmcid: Don't assume CID is CPU owned on mode switch\n\nShinichiro reported a KASAN UAF, which is actually an out of bounds access\nin the MMCID management code.\n\n CPU0\t\t\t\t\t\tCPU1\n \t\t\t\t\t\tT1 runs in userspace\n T0: fork(T4) -> Switch to per CPU CID mode\n fixup() set MM_CID_TRANSIT on T1/CPU1\n T4 exit()\n T3 exit()\n T2 exit()\n\t\t\t\t\t\tT1 exit() switch to per task mode\n\t\t\t\t\t\t ---> Out of bounds access.\n\nAs T1 has not scheduled after T0 set the TRANSIT bit, it exits with the\nTRANSIT bit set. sched_mm_cid_remove_user() clears the TRANSIT bit in\nthe task and drops the CID, but it does not touch the per CPU storage.\nThat's functionally correct because a CID is only owned by the CPU when\nthe ONCPU bit is set, which is mutually exclusive with the TRANSIT flag.\n\nNow sched_mm_cid_exit() assumes that the CID is CPU owned because the\nprior mode was per CPU. It invokes mm_drop_cid_on_cpu() which clears the\nnot set ONCPU bit and then invokes clear_bit() with an insanely large\nbit number because TRANSIT is set (bit 29).\n\nPrevent that by actually validating that the CID is CPU owned in\nmm_drop_cid_on_cpu()." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - The vulnerability is triggered through fork() and exit() syscalls, requiring local access to the system. There is no network or adjacent vector to reach this code path.\nAC:L - The attacker controls both sides of the race - they create and exit threads in their own process. By spawning multiple threads and controlling fork/exit timing, the race condition between mode transition and exit with the TRANSIT bit set is reliably triggerable.\nPR:L - Any unprivileged local user can trigger this by creating a multi-threaded process and having threads fork and exit in specific patterns. No special privileges or capabilities are required.\nUI:N - No user interaction is needed. The attacker can trigger the vulnerability entirely through their own process's fork/exit operations.\nS:U - The vulnerability causes kernel memory corruption within the same security scope. There is no evidence of crossing a security boundary such as VM escape or sandbox escape.\nC:H - The out-of-bounds write (clear_bit at ~64MB offset past the cidmask bitmap) corrupts kernel heap memory. Such kernel memory corruption can be leveraged to create read primitives through corrupted kernel data structures.\nI:H - The bug performs an out-of-bounds clear_bit() at a massive offset (~64MB) into kernel memory, directly corrupting kernel data structures. This arbitrary kernel memory write can be leveraged for control flow hijacking.\nA:H - The out-of-bounds memory access was detected by KASAN as a UAF/OOB, causing a kernel crash. Even without KASAN, writing to arbitrary kernel memory at such a large offset will likely cause a kernel panic or oops." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "kernel/sched/core.c", "kernel/sched/sched.h" ], "versions": [ { "version": "007d84287c7466ca68a5809b616338214dc5b77b", "lessThan": "81f29975631db8a78651b3140ecd0f88ffafc476", "status": "affected", "versionType": "git" }, { "version": "007d84287c7466ca68a5809b616338214dc5b77b", "lessThan": "1e83ccd5921a610ef409a7d4e56db27822b4ea39", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "kernel/sched/core.c", "kernel/sched/sched.h" ], "versions": [ { "version": "6.19", "status": "affected" }, { "version": "0", "lessThan": "6.19", "status": "unaffected", "versionType": "semver" }, { "version": "6.19.1", "lessThanOrEqual": "6.19.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.0", "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": "6.19", "versionEndExcluding": "6.19.1" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "7.0" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/81f29975631db8a78651b3140ecd0f88ffafc476" }, { "url": "https://git.kernel.org/stable/c/1e83ccd5921a610ef409a7d4e56db27822b4ea39" } ], "title": "sched/mmcid: Don't assume CID is CPU owned on mode switch", "x_generator": { "engine": "bippy-1.2.0" } } } }