{"id":"CVE-2025-39888","state":"PUBLISHED","title":"fuse: Block access to folio overlimit","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nfuse: Block access to folio overlimit\n\nsyz reported a slab-out-of-bounds Write in fuse_dev_do_write.\n\nWhen the number of bytes to be retrieved is truncated to the upper limit\nby fc->max_pages and there is an offset, the oob is triggered.\n\nAdd a loop termination condition to prevent overruns.","publishedAt":"2025-09-23T06:00:54.156Z","updatedAt":"2026-08-05T12:05:54.198Z","severity":{"score":7.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"3568a956932621cafadafc8b75fcf6dc06555105","status":"affected","lessThan":"623719227b114d73a2cee45f1b343ced63ce09ec","versionType":"git"},{"version":"3568a956932621cafadafc8b75fcf6dc06555105","status":"affected","lessThan":"9d81ba6d49a7457784f0b6a71046818b86ec7e44","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/fuse/dev.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.16","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.16","versionType":"semver"},{"version":"6.16.8","status":"unaffected","lessThanOrEqual":"6.16.*","versionType":"semver"},{"version":"6.17","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/fuse/dev.c"]}],"references":["https://git.kernel.org/stable/c/623719227b114d73a2cee45f1b343ced63ce09ec","https://git.kernel.org/stable/c/9d81ba6d49a7457784f0b6a71046818b86ec7e44"],"weaknesses":["CWE-787"],"ingestedAt":"2026-10-29T20:09:09.358Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2025/39xxx/CVE-2025-39888.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2025-39888","state":"PUBLISHED","datePublished":"2025-09-23T06:00:54.156Z","dateUpdated":"2026-08-05T12:05:54.198Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2025-04-16T07:20:57.145Z"},"containers":{"cna":{"title":"fuse: Block access to folio overlimit","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nfuse: Block access to folio overlimit\n\nsyz reported a slab-out-of-bounds Write in fuse_dev_do_write.\n\nWhen the number of bytes to be retrieved is truncated to the upper limit\nby fc->max_pages and there is an offset, the oob is triggered.\n\nAdd a loop termination condition to prevent overruns."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"3568a956932621cafadafc8b75fcf6dc06555105","status":"affected","lessThan":"623719227b114d73a2cee45f1b343ced63ce09ec","versionType":"git"},{"version":"3568a956932621cafadafc8b75fcf6dc06555105","status":"affected","lessThan":"9d81ba6d49a7457784f0b6a71046818b86ec7e44","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/fuse/dev.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.16","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.16","versionType":"semver"},{"version":"6.16.8","status":"unaffected","lessThanOrEqual":"6.16.*","versionType":"semver"},{"version":"6.17","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/fuse/dev.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/623719227b114d73a2cee45f1b343ced63ce09ec"},{"url":"https://git.kernel.org/stable/c/9d81ba6d49a7457784f0b6a71046818b86ec7e44"}],"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 reached by a local process writing a FUSE_NOTIFY_RETRIEVE message to an open /dev/fuse file descriptor; no network or physical access is involved.\nAC:L - Every parameter that determines the overflow is attacker-controlled — max_pages and max_write via the FUSE_INIT reply, file size via attribute replies, page-cache residency via FUSE_NOTIFY_STORE, and the intra-page offset via the notify message — making the overflow deterministic and repeatable.\nPR:L - An unprivileged local user suffices: FUSE is flagged FS_USERNS_MOUNT so a mount can be created inside an unprivileged user namespace (unshare -Ur), and the setuid fusermount helper offers the same on typical distros; the notify path itself has no capability check.\nUI:N - The attacker acts as both the FUSE server and the client, populating the page cache from the server side via FUSE_NOTIFY_STORE and issuing the malicious retrieve notification itself, so no victim action is needed.\nS:U - The heap corruption occurs in kernel memory belonging to the same security authority as the attacking process; this is standard kernel privilege escalation with no crossing of a hypervisor or IOMMU boundary.\nC:H - Overwriting descs[0] with a folio pointer yields a ~0xffffea00 byte offset passed to kmap_local_folio(), causing a large out-of-bounds kernel read whose contents are copied straight into the attacker's userspace read() buffer on /dev/fuse.\nI:H - This is a slab out-of-bounds write of 8 attacker-influenced bytes past the kzalloc'd allocation, and because the attacker tunes max_pages to land the allocation exactly on a kmalloc bucket boundary the write corrupts an adjacent slab object — a classic heap-corruption primitive for privilege escalation.\nA:H - The out-of-bounds write plus the resulting wild-pointer read from a bogus folio offset reliably produce memory corruption and an oops/panic, as demonstrated by the KASAN-detected slab-out-of-bounds write in the syzbot reproducer."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T12:05:54.198Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.16","versionEndExcluding":"6.16.8"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.16","versionEndExcluding":"6.17"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"cvssV3_1":{"scope":"UNCHANGED","version":"3.1","baseScore":7.8,"attackVector":"LOCAL","baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","integrityImpact":"HIGH","userInteraction":"NONE","attackComplexity":"LOW","availabilityImpact":"HIGH","privilegesRequired":"LOW","confidentialityImpact":"HIGH"}},{"other":{"type":"ssvc","content":{"id":"CVE-2025-39888","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"version":"2.0.3","timestamp":"2026-01-14T19:26:55.986332Z"}}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-787","lang":"en","type":"CWE","description":"CWE-787 Out-of-bounds Write"}]}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-01-14T19:33:13.183Z"}}]}}}