GHSA-65X4-MV56-GF8M
Vulnerability from github – Published: 2026-03-25 12:30 – Updated: 2026-07-14 15:31In 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.
{
"affected": [],
"aliases": [
"CVE-2026-23319"
],
"database_specific": {
"cwe_ids": [
"CWE-416"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-03-25T11:16:28Z",
"severity": "HIGH"
},
"details": "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.",
"id": "GHSA-65x4-mv56-gf8m",
"modified": "2026-07-14T15:31:41Z",
"published": "2026-03-25T12:30:22Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-23319"
},
{
"type": "WEB",
"url": "https://cert-portal.siemens.com/productcert/html/ssa-019113.html"
},
{
"type": "WEB",
"url": "https://cert-portal.siemens.com/productcert/html/ssa-082556.html"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/3eeddb80191f7626ec1ef742bfff51ec3b0fa5c2"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/4e8a0005d633a4adc98e3b65d5080f93b90d356b"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/529e685e522b9d7fb379dbe6929dcdf520e34c8c"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/56145d237385ca0e7ca9ff7b226aaf2eb8ef368b"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9b02c5c4147f8af8ed783c8deb5df927a55c3951"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/cfcfa0ca0212162aa472551266038e8fd6768cff"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- 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.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.