CVE-2026-90359
bpf: Reject >8 byte return values on return-reading trampoline paths
Published Sep 17, 2026
CVSS n/a
EPSS < 1%
KEV · Not listed
Description
In the Linux kernel, the following vulnerability has been resolved:
bpf: Reject >8 byte return values on return-reading trampoline paths
btf_distill_func_proto() builds the function model used for the
fentry/fexit/fmod_ret/fsession trampolines and struct_ops. It has
accepted a 16-byte __int128 return value since the trampoline was
introduced: __get_type_size() returns the integer's type size, and the
return-type check only rejected ret < 0.
But the BPF trampoline preserves only 8 bytes of the return value (RAX on
x86, i.e. R0). For an attach type that reads the target's return value the
second half (RDX / R3) is neither saved nor restored, so a program
attached to a function returning a 16-byte value corrupts the value seen
by the real caller and itself observes only half of it. struct_ops
trampolines have the same limitation.
This affects the attach types that read the target's return value: fexit,
fmod_ret and fsession (plus the _multi variants of fexit and fsession),
and struct_ops. fentry/fentry_multi run before the target returns and are
unaffected.
Reject a >8 byte return value for these attach types in
bpf_check_attach_target() and bpf_check_attach_btf_id_multi(), and for
struct_ops in bpf_struct_ops_desc_init().
bpf: Reject >8 byte return values on return-reading trampoline paths
btf_distill_func_proto() builds the function model used for the
fentry/fexit/fmod_ret/fsession trampolines and struct_ops. It has
accepted a 16-byte __int128 return value since the trampoline was
introduced: __get_type_size() returns the integer's type size, and the
return-type check only rejected ret < 0.
But the BPF trampoline preserves only 8 bytes of the return value (RAX on
x86, i.e. R0). For an attach type that reads the target's return value the
second half (RDX / R3) is neither saved nor restored, so a program
attached to a function returning a 16-byte value corrupts the value seen
by the real caller and itself observes only half of it. struct_ops
trampolines have the same limitation.
This affects the attach types that read the target's return value: fexit,
fmod_ret and fsession (plus the _multi variants of fexit and fsession),
and struct_ops. fentry/fentry_multi run before the target returns and are
unaffected.
Reject a >8 byte return value for these attach types in
bpf_check_attach_target() and bpf_check_attach_btf_id_multi(), and for
struct_ops in bpf_struct_ops_desc_init().
Affected Products
-
CVE record
-
NVD configurations
No data
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Red Hat packages
No data
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OpenCVE enrichment
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | |||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux | unaffected |
|
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| Linux | Linux | affected |
|
No data.
No data.
| Vendor | Product | Versions | ||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux Kernel |
|
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| Linux | Linux Kernel |
|
Remediation
Tracking
Advisories
| Source | ID | Title |
|---|---|---|
 Debian DLA |
DLA-4904-1 | linux-6.12 security update |
 Ubuntu USN |
USN-9019-1 | Linux kernel (Azure) vulnerabilities |
| Ubuntu USN |
USN-9020-1 | Linux kernel vulnerabilities |
Metrics
No CVSS v4.0
No CVSS v3.1
No CVSS v3.0
No CVSS v2
This CVE is not in the KEV list.
Exploit prediction score: < 1% (0.201% probability within 30 days)
Key SSVC decision points have not yet been added.
References
History
Oct 21, 2026 1:15 PM
Added references
View changes
| Type | Values Removed | Values Added |
|---|---|---|
| References |
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Oct 15, 2026 1:30 PM
Added references
View changes
| Type | Values Removed | Values Added |
|---|---|---|
| References |
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Sep 19, 2026 6:00 AM
Weaknesses updated
View changes
| Type | Values Removed | Values Added |
|---|---|---|
| Weaknesses | CWE-681 |
Sep 17, 2026 4:30 PM
Description updated. Title updated. First appearance in the feed. Affected versions updated. Affected vendors updated. Added references
View changes
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: bpf: Reject >8 byte return values on return-reading trampoline paths btf_distill_func_proto() builds the function model used for the fentry/fexit/fmod_ret/fsession trampolines and struct_ops. It has accepted a 16-byte __int128 return value since the trampoline was introduced: __get_type_size() returns the integer's type size, and the return-type check only rejected ret < 0. But the BPF trampoline preserves only 8 bytes of the return value (RAX on x86, i.e. R0). For an attach type that reads the target's return value the second half (RDX / R3) is neither saved nor restored, so a program attached to a function returning a 16-byte value corrupts the value seen by the real caller and itself observes only half of it. struct_ops trampolines have the same limitation. This affects the attach types that read the target's return value: fexit, fmod_ret and fsession (plus the _multi variants of fexit and fsession), and struct_ops. fentry/fentry_multi run before the target returns and are unaffected. Reject a >8 byte return value for these attach types in bpf_check_attach_target() and bpf_check_attach_btf_id_multi(), and for struct_ops in bpf_struct_ops_desc_init(). | |
| Title | bpf: Reject >8 byte return values on return-reading trampoline paths | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
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Subscriptions
Weaknesses
