bpf: Fix a UAF issue in bpf_trampoline_link_cgroup_shim
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.
CVE-2026-23319
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-23319
Linux
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Linux
Source reference: /containers/cna/affected/1/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "69fd337a975c7e690dfe49d9cb4fe5ba1e6db44e",
"lessThan": "529e685e522b9d7fb379dbe6929dcdf520e34c8c",
"versionType": "git"
},
{
"status": "affected",
"version": "69fd337a975c7e690dfe49d9cb4fe5ba1e6db44e",
"lessThan": "9b02c5c4147f8af8ed783c8deb5df927a55c3951",
"versionType": "git"
},
{
"status": "affected",
"version": "69fd337a975c7e690dfe49d9cb4fe5ba1e6db44e",
"lessThan": "cfcfa0ca0212162aa472551266038e8fd6768cff",
"versionType": "git"
},
{
"status": "affected",
"version": "69fd337a975c7e690dfe49d9cb4fe5ba1e6db44e",
"lessThan": "3eeddb80191f7626ec1ef742bfff51ec3b0fa5c2",
"versionType": "git"
},
{
"status": "affected",
"version": "69fd337a975c7e690dfe49d9cb4fe5ba1e6db44e",
"lessThan": "4e8a0005d633a4adc98e3b65d5080f93b90d356b",
"versionType": "git"
},
{
"status": "affected",
"version": "69fd337a975c7e690dfe49d9cb4fe5ba1e6db44e",
"lessThan": "56145d237385ca0e7ca9ff7b226aaf2eb8ef368b",
"versionType": "git"
}
],
"programFiles": [
"kernel/bpf/trampoline.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "6.0"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "6.0",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "6.1.167",
"versionType": "semver",
"lessThanOrEqual": "6.1.*"
},
{
"status": "unaffected",
"version": "6.6.130",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.12.77",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.17",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "6.19.7",
"versionType": "semver",
"lessThanOrEqual": "6.19.*"
},
{
"status": "unaffected",
"version": "7.0",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"kernel/bpf/trampoline.c"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2026-23319
Source reference:
/cveMetadata/cveId
Publisher severity
No explicit severity was provided.
- Event
- #27226 · Revision 1
- Added to Heist Feed
- Publisher date