VulnerabilityPublished 17 Sep 2026Updated 21 Oct 2026

CVE-2026-90359: Linux kernel · bpf: Reject >8 byte return values on return-reading trampoline paths

Affects Linux kernelSource CVE Database V5

Not known to be exploited · fixed in de54ba33690d2dd3c4aa686c9693505644285b0b : update Linux kernel when convenient.

Data as of 26 Oct 2026, 13:07 UTC

Severity

Unrated

Rated by Threat Radar · CVSS not yet scored by NVD

EPSS: 0.2% chance of exploitation in 30 days – higher than 10% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in de54ba33690d2dd3c4aa686c9693505644285b0b, d36ac53fc83baf843c51b7afd6d2471f36b713d8, c48796aa6c392cde93946e5d5a9a1f1b1cf72feb +1

Exploitation evidence

Disclosed: evidence found.
CVE published 17 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade Linux kernel to de54ba33690d2dd3c4aa686c9693505644285b0b, d36ac53fc83baf843c51b7afd6d2471f36b713d8, c48796aa6c392cde93946e5d5a9a1f1b1cf72feb or 9a9e902bd0556052534641f7d5f868c6dc4b84ae.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ fec56f5890d93fc2ed74166c397dc186b1c25951, < de54ba33690d2dd3c4aa686c9693505644285b0b	Fixed in de54ba33690d2dd3c4aa686c9693505644285b0b
LinuxLinux	Affected ≥ fec56f5890d93fc2ed74166c397dc186b1c25951, < d36ac53fc83baf843c51b7afd6d2471f36b713d8	Fixed in d36ac53fc83baf843c51b7afd6d2471f36b713d8
LinuxLinux	Affected ≥ fec56f5890d93fc2ed74166c397dc186b1c25951, < c48796aa6c392cde93946e5d5a9a1f1b1cf72feb	Fixed in c48796aa6c392cde93946e5d5a9a1f1b1cf72feb
LinuxLinux	Affected ≥ fec56f5890d93fc2ed74166c397dc186b1c25951, < 9a9e902bd0556052534641f7d5f868c6dc4b84ae	Fixed in 9a9e902bd0556052534641f7d5f868c6dc4b84ae
LinuxLinux	Affected =5.5	Fixed in–

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().

References

Community reviews

Loading reviews…