{"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"}}}}