{
  "threat_severity" : "Important",
  "public_date" : "2026-04-03T00:00:00Z",
  "bugzilla" : {
    "description" : "kernel: nfsd: fix heap overflow in NFSv4.0 LOCK replay cache",
    "id" : "2454844",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=2454844"
  },
  "cvss3" : {
    "cvss3_base_score" : "7.8",
    "cvss3_scoring_vector" : "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
    "status" : "verified"
  },
  "cwe" : "CWE-787",
  "details" : [ "In the Linux kernel, the following vulnerability has been resolved:\nnfsd: fix heap overflow in NFSv4.0 LOCK replay cache\nThe NFSv4.0 replay cache uses a fixed 112-byte inline buffer\n(rp_ibuf[NFSD4_REPLAY_ISIZE]) to store encoded operation responses.\nThis size was calculated based on OPEN responses and does not account\nfor LOCK denied responses, which include the conflicting lock owner as\na variable-length field up to 1024 bytes (NFS4_OPAQUE_LIMIT).\nWhen a LOCK operation is denied due to a conflict with an existing lock\nthat has a large owner, nfsd4_encode_operation() copies the full encoded\nresponse into the undersized replay buffer via read_bytes_from_xdr_buf()\nwith no bounds check. This results in a slab-out-of-bounds write of up\nto 944 bytes past the end of the buffer, corrupting adjacent heap memory.\nThis can be triggered remotely by an unauthenticated attacker with two\ncooperating NFSv4.0 clients: one sets a lock with a large owner string,\nthen the other requests a conflicting lock to provoke the denial.\nWe could fix this by increasing NFSD4_REPLAY_ISIZE to allow for a full\nopaque, but that would increase the size of every stateowner, when most\nlockowners are not that large.\nInstead, fix this by checking the encoded response length against\nNFSD4_REPLAY_ISIZE before copying into the replay buffer. If the\nresponse is too large, set rp_buflen to 0 to skip caching the replay\npayload. The status is still cached, and the client already received the\ncorrect response on the original request.", "A flaw was found in the Linux kernel's NFSv4.0 server (nfsd). A remote, unauthenticated attacker can exploit this heap overflow vulnerability in the NFSv4.0 LOCK replay cache. By using two cooperating NFSv4.0 clients, where one sets a lock with a large owner string and another requests a conflicting lock, the attacker can trigger a slab-out-of-bounds write. This corruption of adjacent heap memory could lead to arbitrary code execution or a denial of service." ],
  "statement" : "This Important flaw in the Linux kernel's NFSv4.0 server (nfsd) allows a heap overflow. In this flaw a local attacker can trigger this by orchestrating two NFSv4.0 clients to create a conflicting lock with an oversized owner string.",
  "affected_release" : [ {
    "product_name" : "Red Hat Enterprise Linux 9.4 Extended Update Support",
    "release_date" : "2026-04-23T00:00:00Z",
    "advisory" : "RHSA-2026:10108",
    "cpe" : "cpe:/a:redhat:rhel_eus:9.4",
    "package" : "kernel-0:5.14.0-427.121.1.el9_4"
  }, {
    "product_name" : "Red Hat Enterprise Linux 9.6 Extended Update Support",
    "release_date" : "2026-04-28T00:00:00Z",
    "advisory" : "RHSA-2026:11313",
    "cpe" : "cpe:/a:redhat:rhel_eus:9.6",
    "package" : "kernel-0:5.14.0-570.110.1.el9_6"
  } ],
  "package_state" : [ {
    "product_name" : "Red Hat Enterprise Linux 10",
    "fix_state" : "Affected",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:10"
  }, {
    "product_name" : "Red Hat Enterprise Linux 6",
    "fix_state" : "Affected",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:6"
  }, {
    "product_name" : "Red Hat Enterprise Linux 7",
    "fix_state" : "Affected",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:7"
  }, {
    "product_name" : "Red Hat Enterprise Linux 7",
    "fix_state" : "Affected",
    "package_name" : "kernel-rt",
    "cpe" : "cpe:/o:redhat:enterprise_linux:7"
  }, {
    "product_name" : "Red Hat Enterprise Linux 8",
    "fix_state" : "Affected",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:8"
  }, {
    "product_name" : "Red Hat Enterprise Linux 8",
    "fix_state" : "Affected",
    "package_name" : "kernel-rt",
    "cpe" : "cpe:/o:redhat:enterprise_linux:8"
  }, {
    "product_name" : "Red Hat Enterprise Linux 9",
    "fix_state" : "Affected",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:9"
  }, {
    "product_name" : "Red Hat Enterprise Linux 9",
    "fix_state" : "Affected",
    "package_name" : "kernel-rt",
    "cpe" : "cpe:/o:redhat:enterprise_linux:9"
  } ],
  "references" : [ "https://www.cve.org/CVERecord?id=CVE-2026-31402\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-31402\nhttps://lore.kernel.org/linux-cve-announce/2026040327-CVE-2026-31402-3e6a@gregkh/T" ],
  "name" : "CVE-2026-31402",
  "mitigation" : {
    "value" : "Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.",
    "lang" : "en:us"
  },
  "csaw" : false
}