VulnerabilityPublished 23 Oct 2026

CVE-2026-98950: Linux kernel · flow_dissector: avoid u16 truncation of hlen in bpf_flow_dissect()

Source GCVE Database

Authoritative record:CVE-2026-98950· Medium

Not known to be exploited · fixed in f202578efc738b883cfa04889eb97328914265a7 : update Linux kernel when convenient.

Data as of 26 Oct 2026, 17:16 UTC

Severity

Medium

Rated by Threat Radar · CVSS not yet scored by NVD

EPSS: 0.1% chance of exploitation in 30 days – higher than 7% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in f202578efc738b883cfa04889eb97328914265a7, cc18eb0e9941162c03f03f411ed7f6c339d91fa0, c44c02c930c6583b235a1937c69ff716c4bb4514 +2

Exploitation evidence

Disclosed: evidence found.
CVE published 23 Oct 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.

ghsa-4jwg-g8h6-9gv7

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ d58e468b1112dcd1d5193c0a89ff9f98b5a3e8b9, < f202578efc738b883cfa04889eb97328914265a7	Fixed in f202578efc738b883cfa04889eb97328914265a7
LinuxLinux	Affected ≥ d58e468b1112dcd1d5193c0a89ff9f98b5a3e8b9, < cc18eb0e9941162c03f03f411ed7f6c339d91fa0	Fixed in cc18eb0e9941162c03f03f411ed7f6c339d91fa0
LinuxLinux	Affected ≥ d58e468b1112dcd1d5193c0a89ff9f98b5a3e8b9, < c44c02c930c6583b235a1937c69ff716c4bb4514	Fixed in c44c02c930c6583b235a1937c69ff716c4bb4514
LinuxLinux	Affected ≥ d58e468b1112dcd1d5193c0a89ff9f98b5a3e8b9, < 61b43a51a55929ec040bee3ea51af2121b956d05	Fixed in 61b43a51a55929ec040bee3ea51af2121b956d05
LinuxLinux	Affected ≥ d58e468b1112dcd1d5193c0a89ff9f98b5a3e8b9, < 3fb5ad2951a6df92c98f4f06cd70f20c50a2eb2a	Fixed in 3fb5ad2951a6df92c98f4f06cd70f20c50a2eb2a
LinuxLinux	Affected =4.20	Fixed in–

Description

In the Linux kernel, the following vulnerability has been resolved: flow_dissector: avoid u16 truncation of hlen in bpf_flow_dissect() bpf_flow_dissect() sanitizes the offsets returned by the BPF program with clamp_t(u16, ..., hlen). If hlen is bigger than 65535, the upper bound is truncated before the comparison. For instance, with hlen == 65536, both nhoff and thoff are forced to zero, even if the program returned sane values. This is the same class of bug as the one fixed in commit 99bda1ecbd56 ("flow_dissector: avoid u16 truncation of skb->len when computing thoff"). That fix does not cover the BPF path, because __skb_flow_dissect() returns early when a BPF flow dissector handles the packet. struct bpf_flow_keys stores nhoff and thoff as u16, so cap hlen to U16_MAX before clamping. Found by sashiko while reviewing the commit above.

References

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