{
  "threat_severity" : "Moderate",
  "public_date" : "2026-07-31T00:00:00Z",
  "bugzilla" : {
    "description" : "tar: tar: --one-top-level hardlink targets not confined to top-level directory enabling arbitrary file overwrite",
    "id" : "2509843",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=2509843"
  },
  "cvss3" : {
    "cvss3_base_score" : "4.4",
    "cvss3_scoring_vector" : "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N",
    "status" : "verified"
  },
  "cwe" : "CWE-59",
  "details" : [ "A flaw was found in GNU tar. When extracting an archive with the --one-top-level option, hardlink targets are not confined to the designated top-level directory and may resolve relative to the extraction working directory. A crafted archive can create hardlinks that escape the intended boundary and, when combined with a preexisting symbolic link under the working directory, may allow writing outside that boundary during a single extraction.", "A flaw was found in GNU tar. When extracting an archive with the --one-top-level option, hardlink targets are not confined to the designated top-level directory and may resolve relative to the extraction working directory. A crafted archive can create hardlinks that escape the intended boundary and, when combined with a preexisting symbolic link under the working directory, may allow writing outside that boundary during a single extraction." ],
  "statement" : "Red Hat Enterprise Linux is affected. This issue only applies when the --one-top-level option is used to extract an untrusted archive. Default tar extraction without --one-top-level is not impacted by this specific boundary failure. Users should avoid using --one-top-level as the sole confinement mechanism for untrusted archives until fixed packages are available.",
  "acknowledgement" : "This issue was discovered by Pavel Cahyna (Red Hat).",
  "affected_release" : [ {
    "product_name" : "Red Hat Hardened Images",
    "release_date" : "2026-08-05T00:00:00Z",
    "advisory" : "RHSA-2026:50807",
    "cpe" : "cpe:/a:redhat:hummingbird:1",
    "package" : "tar-main-1.35-9.2.hum1"
  } ],
  "package_state" : [ {
    "product_name" : "Red Hat Enterprise Linux 10",
    "fix_state" : "Affected",
    "package_name" : "tar",
    "cpe" : "cpe:/o:redhat:enterprise_linux:10"
  }, {
    "product_name" : "Red Hat Enterprise Linux 6",
    "fix_state" : "Out of support scope",
    "package_name" : "tar",
    "cpe" : "cpe:/o:redhat:enterprise_linux:6"
  }, {
    "product_name" : "Red Hat Enterprise Linux 7",
    "fix_state" : "Out of support scope",
    "package_name" : "tar",
    "cpe" : "cpe:/o:redhat:enterprise_linux:7"
  }, {
    "product_name" : "Red Hat Enterprise Linux 8",
    "fix_state" : "Fix deferred",
    "package_name" : "tar",
    "cpe" : "cpe:/o:redhat:enterprise_linux:8"
  }, {
    "product_name" : "Red Hat Enterprise Linux 9",
    "fix_state" : "Fix deferred",
    "package_name" : "tar",
    "cpe" : "cpe:/o:redhat:enterprise_linux:9"
  }, {
    "product_name" : "Red Hat Hardened Images",
    "fix_state" : "Not affected",
    "package_name" : "aardvark-dns",
    "cpe" : "cpe:/a:redhat:hummingbird:1"
  }, {
    "product_name" : "Red Hat Hardened Images",
    "fix_state" : "Not affected",
    "package_name" : "chunkah",
    "cpe" : "cpe:/a:redhat:hummingbird:1"
  }, {
    "product_name" : "Red Hat Hardened Images",
    "fix_state" : "Not affected",
    "package_name" : "grafana12.4",
    "cpe" : "cpe:/a:redhat:hummingbird:1"
  }, {
    "product_name" : "Red Hat Hardened Images",
    "fix_state" : "Not affected",
    "package_name" : "grafana13.1",
    "cpe" : "cpe:/a:redhat:hummingbird:1"
  }, {
    "product_name" : "Red Hat Hardened Images",
    "fix_state" : "Not affected",
    "package_name" : "netavark",
    "cpe" : "cpe:/a:redhat:hummingbird:1"
  }, {
    "product_name" : "Red Hat Hardened Images",
    "fix_state" : "Not affected",
    "package_name" : "nodejs26",
    "cpe" : "cpe:/a:redhat:hummingbird:1"
  }, {
    "product_name" : "Red Hat Hardened Images",
    "fix_state" : "Not affected",
    "package_name" : "python-cryptography",
    "cpe" : "cpe:/a:redhat:hummingbird:1"
  }, {
    "product_name" : "Red Hat Hardened Images",
    "fix_state" : "Not affected",
    "package_name" : "rust",
    "cpe" : "cpe:/a:redhat:hummingbird:1"
  }, {
    "product_name" : "Red Hat Hardened Images",
    "fix_state" : "Not affected",
    "package_name" : "rust-rpm-sequoia",
    "cpe" : "cpe:/a:redhat:hummingbird:1"
  }, {
    "product_name" : "Red Hat Hardened Images",
    "fix_state" : "Not affected",
    "package_name" : "yarnpkg",
    "cpe" : "cpe:/a:redhat:hummingbird:1"
  }, {
    "product_name" : "Red Hat OpenShift Container Platform 4",
    "fix_state" : "Fix deferred",
    "package_name" : "rhcos",
    "cpe" : "cpe:/a:redhat:openshift:4"
  } ],
  "references" : [ "https://www.cve.org/CVERecord?id=CVE-2026-18508\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-18508" ],
  "name" : "CVE-2026-18508",
  "mitigation" : {
    "value" : "Do not use --one-top-level as the sole confinement mechanism when extracting untrusted archives. Prefer extracting as an unprivileged user into a freshly created empty directory after changing into that directory (mkdir and cd), avoid extracting as root from sensitive working directories such as /, and follow the GNU tar security guidance for untrusted archives.",
    "lang" : "en:us"
  },
  "csaw" : false
}