{"id":"CVE-2026-23319","title":"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 'bpf_link_put' reduces the\nrefcount of 'shim_link->link.link' to zero, …","summary":"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 'bpf_link_put' reduces the\nrefcount of 'shim_link->link.link' to zero, …","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","cwe":["CWE-416"],"vendor":"linux","product":"linux_kernel","affected":["linux_kernel >= 6.0.1, < 6.1.167","linux_kernel >= 6.2, < 6.6.130","linux_kernel >= 6.7, < 6.12.77","linux_kernel >= 6.13, < 6.18.17","linux_kernel >= 6.19, < 6.19.7","linux_kernel = 6.0","linux_kernel = 7.0"],"patched":["linux_kernel 6.19.7"],"published":"2026-03-25","updated":"2026-10-15","sourceUpdated":"2026-10-15T02:18:49.593","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-23319","references":[{"url":"https://git.kernel.org/stable/c/3eeddb80191f7626ec1ef742bfff51ec3b0fa5c2","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/4e8a0005d633a4adc98e3b65d5080f93b90d356b","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/529e685e522b9d7fb379dbe6929dcdf520e34c8c","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/56145d237385ca0e7ca9ff7b226aaf2eb8ef368b","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/9b02c5c4147f8af8ed783c8deb5df927a55c3951","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/cfcfa0ca0212162aa472551266038e8fd6768cff","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-019113.html","label":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-082556.html","label":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-457936.html","label":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-784472.html","label":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"}],"tags":["nvd","cve.org"],"epss":0.00136,"epssPercentile":0.0304,"ingestedAt":"2026-09-08T15:33:26.993Z","slug":"CVE-2026-23319","body":"## Overview\n\nIn 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 'bpf_link_put' reduces the\nrefcount of 'shim_link->link.link' to zero, the resource is considered\nreleased but may still be referenced via 'tr->progs_hlist' in\n'cgroup_shim_find'. The actual cleanup of 'tr->progs_hlist' in\n'bpf_shim_tramp_link_release' is deferred. During this window, another\nprocess can cause a use-after-free via 'bpf_trampoline_link_cgroup_shim'.\n\nBased on Martin KaFai Lau's suggestions, I have created a simple patch.\n\nTo fix this:\n   Add an atomic non-zero check in 'bpf_trampoline_link_cgroup_shim'.\n   Only increment the refcount if it is not already zero.\n\nTesting:\n   I verified the fix by adding a delay in\n   'bpf_shim_tramp_link_release' 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->trampoline)\n\t\treturn;\n\n+\tmsleep(100);\n\tWARN_ON_ONCE(bpf_trampoline_unlink_prog(&shim_link->link,\n\t\tshim_link->trampoline, NULL));\n\tbpf_trampoline_put(shim_link->trampoline);\n}\n\nBefore the patch, running a PoC easily reproduced the crash(almost 100%)\nwith a call trace similar to KaiyanM's report.\nAfter the patch, the bug no longer occurs even after millions of\niterations.\n\n## Affected\n\n- `linux_kernel >= 6.0.1, < 6.1.167`\n- `linux_kernel >= 6.2, < 6.6.130`\n- `linux_kernel >= 6.7, < 6.12.77`\n- `linux_kernel >= 6.13, < 6.18.17`\n- `linux_kernel >= 6.19, < 6.19.7`\n- `linux_kernel = 6.0`\n- `linux_kernel = 7.0`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `linux_kernel 6.19.7`","depth":"twilight","depthScore":43,"depthScoreParts":{"impact":42.9,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[{"seq":221657,"id":"CVE-2026-23319","ts":1792035308568,"field":"cvss","old":null,"new":"7.8"},{"seq":221656,"id":"CVE-2026-23319","ts":1792035308568,"field":"severity","old":"none","new":"high"}]}