VulnerabilityPublished 25 Sep 2026Updated 21 Oct 2026

CVE-2026-98049: Linux kernel · bpf: zero extend the result of an arena 32-bit cmpxchg

Affects Linux kernelSource CVE Database V5

Not known to be exploited · fixed in 4814ed6406f3493bd554ad046da5f7fc04833571 : update Linux kernel when convenient.

Data as of 26 Oct 2026, 14:18 UTC

Severity

Unrated

Rated by Threat Radar · CVSS not yet scored by NVD

EPSS: 0.1% chance of exploitation in 30 days – higher than 4% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 4814ed6406f3493bd554ad046da5f7fc04833571, 6bb6ae5ab1beffda51dabf41612f501d07f10fc6, 1c1b476d43a8b6c9bc04600369dd8cc39950d98e +1

Exploitation evidence

Disclosed: evidence found.
CVE published 25 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 4814ed6406f3493bd554ad046da5f7fc04833571, 6bb6ae5ab1beffda51dabf41612f501d07f10fc6, 1c1b476d43a8b6c9bc04600369dd8cc39950d98e or 1bb1be18263995b159cf5afad3a05500ba6d2a7b.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ d503a04f8bc0c75dc9db9452d8cc79d748afb752, < 4814ed6406f3493bd554ad046da5f7fc04833571	Fixed in 4814ed6406f3493bd554ad046da5f7fc04833571
LinuxLinux	Affected ≥ d503a04f8bc0c75dc9db9452d8cc79d748afb752, < 6bb6ae5ab1beffda51dabf41612f501d07f10fc6	Fixed in 6bb6ae5ab1beffda51dabf41612f501d07f10fc6
LinuxLinux	Affected ≥ d503a04f8bc0c75dc9db9452d8cc79d748afb752, < 1c1b476d43a8b6c9bc04600369dd8cc39950d98e	Fixed in 1c1b476d43a8b6c9bc04600369dd8cc39950d98e
LinuxLinux	Affected ≥ d503a04f8bc0c75dc9db9452d8cc79d748afb752, < 1bb1be18263995b159cf5afad3a05500ba6d2a7b	Fixed in 1bb1be18263995b159cf5afad3a05500ba6d2a7b
LinuxLinux	Affected =6.10	Fixed in–

Description

In the Linux kernel, the following vulnerability has been resolved: bpf: zero extend the result of an arena 32-bit cmpxchg bpf_convert_ctx_accesses() rewrites an atomic on an arena pointer from BPF_STX | BPF_ATOMIC to BPF_STX | BPF_PROBE_ATOMIC, and it runs before bpf_opt_subreg_zext_lo32_rnd_hi32(). That pass emits an explicit zero extension for a 32-bit cmpxchg even when bpf_jit_needs_zext() is false. This is done because on some architectures 32-bit cmpxchg requires explicit zero extension for the dst register. E.g. on x86-64 'lock cmpxchg' does not change the %eax if comparison is successful, while BPF semantics declare that each operation on a 32-bit register zero extends it's upper half. is_cmpxchg_insn() matches BPF_MODE == BPF_ATOMIC only, so an arena cmpxchg misses said zero extension adjustment. This patch adjusts is_cmpxchg_insn() to match BPF_PROBE_ATOMIC alongside BPF_ATOMIC.

References

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