{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-23077", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-01-13T15:37:45.959Z", "datePublished": "2026-02-04T16:08:02.274Z", "dateUpdated": "2026-08-05T12:20:13.107Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T12:20:13.107Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm/vma: fix anon_vma UAF on mremap() faulted, unfaulted merge\n\nPatch series \"mm/vma: fix anon_vma UAF on mremap() faulted, unfaulted\nmerge\", v2.\n\nCommit 879bca0a2c4f (\"mm/vma: fix incorrectly disallowed anonymous VMA\nmerges\") introduced the ability to merge previously unavailable VMA merge\nscenarios.\n\nHowever, it is handling merges incorrectly when it comes to mremap() of a\nfaulted VMA adjacent to an unfaulted VMA. The issues arise in three\ncases:\n\n1. Previous VMA unfaulted:\n\n copied -----|\n v\n\t|-----------|.............|\n\t| unfaulted |(faulted VMA)|\n\t|-----------|.............|\n\t prev\n\n2. Next VMA unfaulted:\n\n copied -----|\n v\n\t |.............|-----------|\n\t |(faulted VMA)| unfaulted |\n |.............|-----------|\n\t\t next\n\n3. Both adjacent VMAs unfaulted:\n\n copied -----|\n v\n\t|-----------|.............|-----------|\n\t| unfaulted |(faulted VMA)| unfaulted |\n\t|-----------|.............|-----------|\n\t prev next\n\nThis series fixes each of these cases, and introduces self tests to assert\nthat the issues are corrected.\n\nI also test a further case which was already handled, to assert that my\nchanges continues to correctly handle it:\n\n4. prev unfaulted, next faulted:\n\n copied -----|\n v\n\t|-----------|.............|-----------|\n\t| unfaulted |(faulted VMA)| faulted |\n\t|-----------|.............|-----------|\n\t prev next\n\nThis bug was discovered via a syzbot report, linked to in the first patch\nin the series, I confirmed that this series fixes the bug.\n\nI also discovered that we are failing to check that the faulted VMA was\nnot forked when merging a copied VMA in cases 1-3 above, an issue this\nseries also addresses.\n\nI also added self tests to assert that this is resolved (and confirmed\nthat the tests failed prior to this).\n\nI also cleaned up vma_expand() as part of this work, renamed\nvma_had_uncowed_parents() to vma_is_fork_child() as the previous name was\nunduly confusing, and simplified the comments around this function.\n\n\nThis patch (of 4):\n\nCommit 879bca0a2c4f (\"mm/vma: fix incorrectly disallowed anonymous VMA\nmerges\") introduced the ability to merge previously unavailable VMA merge\nscenarios.\n\nThe key piece of logic introduced was the ability to merge a faulted VMA\nimmediately next to an unfaulted VMA, which relies upon dup_anon_vma() to\ncorrectly handle anon_vma state.\n\nIn the case of the merge of an existing VMA (that is changing properties\nof a VMA and then merging if those properties are shared by adjacent\nVMAs), dup_anon_vma() is invoked correctly.\n\nHowever in the case of the merge of a new VMA, a corner case peculiar to\nmremap() was missed.\n\nThe issue is that vma_expand() only performs dup_anon_vma() if the target\n(the VMA that will ultimately become the merged VMA): is not the next VMA,\ni.e. the one that appears after the range in which the new VMA is to be\nestablished.\n\nA key insight here is that in all other cases other than mremap(), a new\nVMA merge either expands an existing VMA, meaning that the target VMA will\nbe that VMA, or would have anon_vma be NULL.\n\nSpecifically:\n\n* __mmap_region() - no anon_vma in place, initial mapping.\n* do_brk_flags() - expanding an existing VMA.\n* vma_merge_extend() - expanding an existing VMA.\n* relocate_vma_down() - no anon_vma in place, initial mapping.\n\nIn addition, we are in the unique situation of needing to duplicate\nanon_vma state from a VMA that is neither the previous or next VMA being\nmerged with.\n\ndup_anon_vma() deals exclusively with the target=unfaulted, src=faulted\ncase. This leaves four possibilities, in each case where the copied VMA\nis faulted:\n\n1. Previous VMA unfaulted:\n\n copied -----|\n \n---truncated---" } ], "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 via the mremap() syscall, which requires local access to the system. There is no network or adjacent network path to reach this code.\nAC:L - The attacker can deterministically set up the required VMA layout (faulted VMA adjacent to unfaulted VMA) and trigger the bug with mremap(MREMAP_DONTUNMAP). Syzbot found this automatically, confirming reliable reproducibility.\nPR:L - The mremap() syscall is available to any unprivileged local user. No special capabilities or root privileges are required to trigger this vulnerability.\nUI:N - No user interaction is required. The attacker can trigger the vulnerability entirely through their own syscall sequence.\nS:U - This is a standard kernel memory corruption vulnerability. It does not cross security boundaries like VM escape or IOMMU bypass.\nC:H - The use-after-free on anon_vma gives the attacker control over freed object contents via heap spraying, enabling arbitrary kernel memory reads through the dangling folio references.\nI:H - The use-after-free enables heap spraying where attacker-controlled data replaces the freed anon_vma, providing arbitrary write primitives and potential control flow hijacking through corrupted kernel structures.\nA:H - The use-after-free causes kernel crashes when the dangling anon_vma pointers are accessed, leading to kernel oops or panic. Syzbot confirmed crashes from this bug." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "mm/vma.c", "mm/vma.h" ], "versions": [ { "version": "879bca0a2c4f40b08d09a95a2a0c3c6513060b5c", "lessThan": "a4d9dbfc1bab16e25fefd34b5e537a46bed8fc96", "status": "affected", "versionType": "git" }, { "version": "879bca0a2c4f40b08d09a95a2a0c3c6513060b5c", "lessThan": "61f67c230a5e7c741c352349ea80147fbe65bfae", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "mm/vma.c", "mm/vma.h" ], "versions": [ { "version": "6.16", "status": "affected" }, { "version": "0", "lessThan": "6.16", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.8", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.19", "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": "6.16", "versionEndExcluding": "6.18.8" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.16", "versionEndExcluding": "6.19" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/a4d9dbfc1bab16e25fefd34b5e537a46bed8fc96" }, { "url": "https://git.kernel.org/stable/c/61f67c230a5e7c741c352349ea80147fbe65bfae" } ], "title": "mm/vma: fix anon_vma UAF on mremap() faulted, unfaulted merge", "x_generator": { "engine": "bippy-1.2.0" } } } }