CVE-2025-71080 (GCVE-0-2025-71080)

Vulnerability from cvelistv5 – Published: 2026-01-13 15:34 – Updated: 2026-01-13 15:34
VLAI?
Title
ipv6: fix a BUG in rt6_get_pcpu_route() under PREEMPT_RT
Summary
In the Linux kernel, the following vulnerability has been resolved: ipv6: fix a BUG in rt6_get_pcpu_route() under PREEMPT_RT On PREEMPT_RT kernels, after rt6_get_pcpu_route() returns NULL, the current task can be preempted. Another task running on the same CPU may then execute rt6_make_pcpu_route() and successfully install a pcpu_rt entry. When the first task resumes execution, its cmpxchg() in rt6_make_pcpu_route() will fail because rt6i_pcpu is no longer NULL, triggering the BUG_ON(prev). It's easy to reproduce it by adding mdelay() after rt6_get_pcpu_route(). Using preempt_disable/enable is not appropriate here because ip6_rt_pcpu_alloc() may sleep. Fix this by handling the cmpxchg() failure gracefully on PREEMPT_RT: free our allocation and return the existing pcpu_rt installed by another task. The BUG_ON is replaced by WARN_ON_ONCE for non-PREEMPT_RT kernels where such races should not occur.
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: d2d6422f8bd17c6bb205133e290625a564194496 , < 1dc33ad0867325f8d2c6d7b2a6f542d4f3121f66 (git)
Affected: d2d6422f8bd17c6bb205133e290625a564194496 , < 787515ccb2292f82eb0876993129154629a49651 (git)
Affected: d2d6422f8bd17c6bb205133e290625a564194496 , < 1adaea51c61b52e24e7ab38f7d3eba023b2d050d (git)
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    Linux Linux Affected: 6.12
Unaffected: 0 , < 6.12 (semver)
Unaffected: 6.12.64 , ≤ 6.12.* (semver)
Unaffected: 6.18.4 , ≤ 6.18.* (semver)
Unaffected: 6.19-rc4 , ≤ * (original_commit_for_fix)
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{
  "containers": {
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      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/ipv6/route.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
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          "vendor": "Linux",
          "versions": [
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            {
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              "status": "unaffected",
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              "versionType": "semver"
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            {
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              "version": "6.19-rc4",
              "versionType": "original_commit_for_fix"
            }
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      "cpeApplicability": [
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              "negate": false,
              "operator": "OR"
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: fix a BUG in rt6_get_pcpu_route() under PREEMPT_RT\n\nOn PREEMPT_RT kernels, after rt6_get_pcpu_route() returns NULL, the\ncurrent task can be preempted. Another task running on the same CPU\nmay then execute rt6_make_pcpu_route() and successfully install a\npcpu_rt entry. When the first task resumes execution, its cmpxchg()\nin rt6_make_pcpu_route() will fail because rt6i_pcpu is no longer\nNULL, triggering the BUG_ON(prev). It\u0027s easy to reproduce it by adding\nmdelay() after rt6_get_pcpu_route().\n\nUsing preempt_disable/enable is not appropriate here because\nip6_rt_pcpu_alloc() may sleep.\n\nFix this by handling the cmpxchg() failure gracefully on PREEMPT_RT:\nfree our allocation and return the existing pcpu_rt installed by\nanother task. The BUG_ON is replaced by WARN_ON_ONCE for non-PREEMPT_RT\nkernels where such races should not occur."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-01-13T15:34:44.832Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/1dc33ad0867325f8d2c6d7b2a6f542d4f3121f66"
        },
        {
          "url": "https://git.kernel.org/stable/c/787515ccb2292f82eb0876993129154629a49651"
        },
        {
          "url": "https://git.kernel.org/stable/c/1adaea51c61b52e24e7ab38f7d3eba023b2d050d"
        }
      ],
      "title": "ipv6: fix a BUG in rt6_get_pcpu_route() under PREEMPT_RT",
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  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-71080",
    "datePublished": "2026-01-13T15:34:44.832Z",
    "dateReserved": "2026-01-13T15:30:19.648Z",
    "dateUpdated": "2026-01-13T15:34:44.832Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "nvd": "{\"cve\":{\"id\":\"CVE-2025-71080\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-01-13T16:16:07.550\",\"lastModified\":\"2026-01-13T16:16:07.550\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nipv6: fix a BUG in rt6_get_pcpu_route() under PREEMPT_RT\\n\\nOn PREEMPT_RT kernels, after rt6_get_pcpu_route() returns NULL, the\\ncurrent task can be preempted. Another task running on the same CPU\\nmay then execute rt6_make_pcpu_route() and successfully install a\\npcpu_rt entry. When the first task resumes execution, its cmpxchg()\\nin rt6_make_pcpu_route() will fail because rt6i_pcpu is no longer\\nNULL, triggering the BUG_ON(prev). It\u0027s easy to reproduce it by adding\\nmdelay() after rt6_get_pcpu_route().\\n\\nUsing preempt_disable/enable is not appropriate here because\\nip6_rt_pcpu_alloc() may sleep.\\n\\nFix this by handling the cmpxchg() failure gracefully on PREEMPT_RT:\\nfree our allocation and return the existing pcpu_rt installed by\\nanother task. The BUG_ON is replaced by WARN_ON_ONCE for non-PREEMPT_RT\\nkernels where such races should not occur.\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/1adaea51c61b52e24e7ab38f7d3eba023b2d050d\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/1dc33ad0867325f8d2c6d7b2a6f542d4f3121f66\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/787515ccb2292f82eb0876993129154629a49651\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


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