{
  "cveId": "CVE-2026-23077",
  "url": "https://patchblox.com/security/cve/CVE-2026-23077",
  "summary": "CVE-2026-23077 is fixed in linux on 1 platform by DEBIAN-CVE-2026-23077 (version 6.18.8-1), released February 4, 2026. It is not reported as exploited. Patch Radar priority: High.",
  "title": "linux: In the Linux kernel, the following vulnerability has been resolved:  mm/vma: fix anon_vma UAF on mremap() faulted, un...",
  "description": "In the Linux kernel, the following vulnerability has been resolved:  mm/vma: fix anon_vma UAF on mremap() faulted, unfaulted merge  Patch series \u0022mm/vma: fix anon_vma UAF on mremap() faulted, unfaulted merge\u0022, v2.  Commit 879bca0a2c4f (\u0022mm/vma: fix incorrectly disallowed anonymous VMA merges\u0022) introduced the ability to merge previously unavailable VMA merge scenarios.  However, it is handling merges incorrectly when it comes to mremap() of a faulted VMA adjacent to an unfaulted VMA.  The issues arise in three cases:  1. Previous VMA unfaulted:                copied -----|                           v \t|-----------|.............| \t| unfaulted |(faulted VMA)| \t|-----------|.............| \t     prev  2. Next VMA unfaulted:                copied -----|                           v \t            |.............|-----------| \t            |(faulted VMA)| unfaulted |                     |.............|-----------| \t\t                      next  3. Both adjacent VMAs unfaulted:                copied -----|                           v \t|-----------|.............|-----------| \t| unfaulted |(faulted VMA)| unfaulted | \t|-----------|.............|-----------| \t     prev                      next  This series fixes each of these cases, and introduces self tests to assert that the issues are corrected.  I also test a further case which was already handled, to assert that my changes continues to correctly handle it:  4. prev unfaulted, next faulted:                copied -----|                           v \t|-----------|.............|-----------| \t| unfaulted |(faulted VMA)|  faulted  | \t|-----------|.............|-----------| \t     prev                      next  This bug was discovered via a syzbot report, linked to in the first patch in the series, I confirmed that this series fixes the bug.  I also discovered that we are failing to check that the faulted VMA was not forked when merging a copied VMA in cases 1-3 above, an issue this series also addresses.  I also added self tests to assert that this is resolved (and confirmed that the tests failed prior to this).  I also cleaned up vma_expand() as part of this work, renamed vma_had_uncowed_parents() to vma_is_fork_child() as the previous name was unduly confusing, and simplified the comments around this function.   This patch (of 4):  Commit 879bca0a2c4f (\u0022mm/vma: fix incorrectly disallowed anonymous VMA merges\u0022) introduced the ability to merge previously unavailable VMA merge scenarios.  The key piece of logic introduced was the ability to merge a faulted VMA immediately next to an unfaulted VMA, which relies upon dup_anon_vma() to correctly handle anon_vma state.  In the case of the merge of an existing VMA (that is changing properties of a VMA and then merging if those properties are shared by adjacent VMAs), dup_anon_vma() is invoked correctly.  However in the case of the merge of a new VMA, a corner case peculiar to mremap() was missed.  The issue is that vma_expand() only performs dup_anon_vma() if the target (the VMA that will ultimately become the merged VMA): is not the next VMA, i.e.  the one that appears after the range in which the new VMA is to be established.  A key insight here is that in all other cases other than mremap(), a new VMA merge either expands an existing VMA, meaning that the target VMA will be that VMA, or would have anon_vma be NULL.  Specifically:  * __mmap_region() - no anon_vma in place, initial mapping. * do_brk_flags() - expanding an existing VMA. * vma_merge_extend() - expanding an existing VMA. * relocate_vma_down() - no anon_vma in place, initial mapping.  In addition, we are in the unique situation of needing to duplicate anon_vma state from a VMA that is neither the previous or next VMA being merged with.  dup_anon_vma() deals exclusively with the target=unfaulted, src=faulted case.  This leaves four possibilities, in each case where the copied VMA is faulted:  1. Previous VMA unfaulted:                copied -----|                         ---truncated---",
  "published": "2026-02-04T17:16:18Z",
  "severity": "high",
  "cvss": 7.8,
  "cvssVector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
  "epss": 0.0016,
  "epssPercentile": 0.05232,
  "priority": "High",
  "priorityTier": 3,
  "exploited": false,
  "vendorExploited": false,
  "disclosed": false,
  "fixes": [
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 14",
      "fixedVersion": "6.18.8-1",
      "fix": "DEBIAN-CVE-2026-23077",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-23077",
      "released": "2026-02-04T17:16:18Z"
    }
  ],
  "noFixYet": [],
  "dataAsOf": "2026-11-08T19:12:23Z",
  "attribution": {
    "text": "Data: Patchblox Patch Radar",
    "url": "https://patchblox.com/security/patch-radar",
    "terms": "https://patchblox.com/security/patch-radar/use-the-data"
  }
}