CVE-2026-23319 (GCVE-0-2026-23319)

Vulnerability from cvelistv5 – Published: 2026-03-25 10:27 – Updated: 2026-03-25 10:27
VLAI?
Title
bpf: Fix a UAF issue in bpf_trampoline_link_cgroup_shim
Summary
In the Linux kernel, the following vulnerability has been resolved: bpf: Fix a UAF issue in bpf_trampoline_link_cgroup_shim The root cause of this bug is that when 'bpf_link_put' reduces the refcount of 'shim_link->link.link' to zero, the resource is considered released but may still be referenced via 'tr->progs_hlist' in 'cgroup_shim_find'. The actual cleanup of 'tr->progs_hlist' in 'bpf_shim_tramp_link_release' is deferred. During this window, another process can cause a use-after-free via 'bpf_trampoline_link_cgroup_shim'. Based on Martin KaFai Lau's suggestions, I have created a simple patch. To fix this: Add an atomic non-zero check in 'bpf_trampoline_link_cgroup_shim'. Only increment the refcount if it is not already zero. Testing: I verified the fix by adding a delay in 'bpf_shim_tramp_link_release' to make the bug easier to trigger: static void bpf_shim_tramp_link_release(struct bpf_link *link) { /* ... */ if (!shim_link->trampoline) return; + msleep(100); WARN_ON_ONCE(bpf_trampoline_unlink_prog(&shim_link->link, shim_link->trampoline, NULL)); bpf_trampoline_put(shim_link->trampoline); } Before the patch, running a PoC easily reproduced the crash(almost 100%) with a call trace similar to KaiyanM's report. After the patch, the bug no longer occurs even after millions of iterations.
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 69fd337a975c7e690dfe49d9cb4fe5ba1e6db44e , < 529e685e522b9d7fb379dbe6929dcdf520e34c8c (git)
Affected: 69fd337a975c7e690dfe49d9cb4fe5ba1e6db44e , < 9b02c5c4147f8af8ed783c8deb5df927a55c3951 (git)
Affected: 69fd337a975c7e690dfe49d9cb4fe5ba1e6db44e , < cfcfa0ca0212162aa472551266038e8fd6768cff (git)
Affected: 69fd337a975c7e690dfe49d9cb4fe5ba1e6db44e , < 3eeddb80191f7626ec1ef742bfff51ec3b0fa5c2 (git)
Affected: 69fd337a975c7e690dfe49d9cb4fe5ba1e6db44e , < 4e8a0005d633a4adc98e3b65d5080f93b90d356b (git)
Affected: 69fd337a975c7e690dfe49d9cb4fe5ba1e6db44e , < 56145d237385ca0e7ca9ff7b226aaf2eb8ef368b (git)
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    Linux Linux Affected: 6.0
Unaffected: 0 , < 6.0 (semver)
Unaffected: 6.1.167 , ≤ 6.1.* (semver)
Unaffected: 6.6.130 , ≤ 6.6.* (semver)
Unaffected: 6.12.77 , ≤ 6.12.* (semver)
Unaffected: 6.18.17 , ≤ 6.18.* (semver)
Unaffected: 6.19.7 , ≤ 6.19.* (semver)
Unaffected: 7.0-rc3 , ≤ * (original_commit_for_fix)
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{
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          "programFiles": [
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Fix a UAF issue in bpf_trampoline_link_cgroup_shim\n\nThe root cause of this bug is that when \u0027bpf_link_put\u0027 reduces the\nrefcount of \u0027shim_link-\u003elink.link\u0027 to zero, the resource is considered\nreleased but may still be referenced via \u0027tr-\u003eprogs_hlist\u0027 in\n\u0027cgroup_shim_find\u0027. The actual cleanup of \u0027tr-\u003eprogs_hlist\u0027 in\n\u0027bpf_shim_tramp_link_release\u0027 is deferred. During this window, another\nprocess can cause a use-after-free via \u0027bpf_trampoline_link_cgroup_shim\u0027.\n\nBased on Martin KaFai Lau\u0027s suggestions, I have created a simple patch.\n\nTo fix this:\n   Add an atomic non-zero check in \u0027bpf_trampoline_link_cgroup_shim\u0027.\n   Only increment the refcount if it is not already zero.\n\nTesting:\n   I verified the fix by adding a delay in\n   \u0027bpf_shim_tramp_link_release\u0027 to make the bug easier to trigger:\n\nstatic void bpf_shim_tramp_link_release(struct bpf_link *link)\n{\n\t/* ... */\n\tif (!shim_link-\u003etrampoline)\n\t\treturn;\n\n+\tmsleep(100);\n\tWARN_ON_ONCE(bpf_trampoline_unlink_prog(\u0026shim_link-\u003elink,\n\t\tshim_link-\u003etrampoline, NULL));\n\tbpf_trampoline_put(shim_link-\u003etrampoline);\n}\n\nBefore the patch, running a PoC easily reproduced the crash(almost 100%)\nwith a call trace similar to KaiyanM\u0027s report.\nAfter the patch, the bug no longer occurs even after millions of\niterations."
        }
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      "providerMetadata": {
        "dateUpdated": "2026-03-25T10:27:13.678Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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    "cveId": "CVE-2026-23319",
    "datePublished": "2026-03-25T10:27:13.678Z",
    "dateReserved": "2026-01-13T15:37:45.995Z",
    "dateUpdated": "2026-03-25T10:27:13.678Z",
    "state": "PUBLISHED"
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    "nvd": "{\"cve\":{\"id\":\"CVE-2026-23319\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-03-25T11:16:28.570\",\"lastModified\":\"2026-03-25T15:41:33.977\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nbpf: Fix a UAF issue in bpf_trampoline_link_cgroup_shim\\n\\nThe root cause of this bug is that when \u0027bpf_link_put\u0027 reduces the\\nrefcount of \u0027shim_link-\u003elink.link\u0027 to zero, the resource is considered\\nreleased but may still be referenced via \u0027tr-\u003eprogs_hlist\u0027 in\\n\u0027cgroup_shim_find\u0027. The actual cleanup of \u0027tr-\u003eprogs_hlist\u0027 in\\n\u0027bpf_shim_tramp_link_release\u0027 is deferred. During this window, another\\nprocess can cause a use-after-free via \u0027bpf_trampoline_link_cgroup_shim\u0027.\\n\\nBased on Martin KaFai Lau\u0027s suggestions, I have created a simple patch.\\n\\nTo fix this:\\n   Add an atomic non-zero check in \u0027bpf_trampoline_link_cgroup_shim\u0027.\\n   Only increment the refcount if it is not already zero.\\n\\nTesting:\\n   I verified the fix by adding a delay in\\n   \u0027bpf_shim_tramp_link_release\u0027 to make the bug easier to trigger:\\n\\nstatic void bpf_shim_tramp_link_release(struct bpf_link *link)\\n{\\n\\t/* ... */\\n\\tif (!shim_link-\u003etrampoline)\\n\\t\\treturn;\\n\\n+\\tmsleep(100);\\n\\tWARN_ON_ONCE(bpf_trampoline_unlink_prog(\u0026shim_link-\u003elink,\\n\\t\\tshim_link-\u003etrampoline, NULL));\\n\\tbpf_trampoline_put(shim_link-\u003etrampoline);\\n}\\n\\nBefore the patch, running a PoC easily reproduced the crash(almost 100%)\\nwith a call trace similar to KaiyanM\u0027s report.\\nAfter the patch, the bug no longer occurs even after millions of\\niterations.\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/3eeddb80191f7626ec1ef742bfff51ec3b0fa5c2\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/4e8a0005d633a4adc98e3b65d5080f93b90d356b\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/529e685e522b9d7fb379dbe6929dcdf520e34c8c\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/56145d237385ca0e7ca9ff7b226aaf2eb8ef368b\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/9b02c5c4147f8af8ed783c8deb5df927a55c3951\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/cfcfa0ca0212162aa472551266038e8fd6768cff\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


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  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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