VulnerabilityPublished 18 Oct 2026Updated 21 Oct 2026

CVE-2026-98851: Linux kernel · netfilter: nft_flow_offload: drop flowtable reference on init error path

Affects Linux kernelSource CVE Database V5

Not known to be exploited · fixed in c5f91098edee98c015f78488460a0609e62582a5 : 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: 0.1% chance of exploitation in 30 days – higher than 5% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in c5f91098edee98c015f78488460a0609e62582a5, 747928b5d4ff8c8de55138a54c13980e4bb88578, 64ac0cb574c740bf723affb79b646eeba920db6b +2

Exploitation evidence

Disclosed: evidence found.
CVE published 18 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.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ a3c90f7a2323b331ae816d5b0633e68148e25d04, < c5f91098edee98c015f78488460a0609e62582a5	Fixed in c5f91098edee98c015f78488460a0609e62582a5
LinuxLinux	Affected ≥ a3c90f7a2323b331ae816d5b0633e68148e25d04, < 747928b5d4ff8c8de55138a54c13980e4bb88578	Fixed in 747928b5d4ff8c8de55138a54c13980e4bb88578
LinuxLinux	Affected ≥ a3c90f7a2323b331ae816d5b0633e68148e25d04, < 64ac0cb574c740bf723affb79b646eeba920db6b	Fixed in 64ac0cb574c740bf723affb79b646eeba920db6b
LinuxLinux	Affected ≥ a3c90f7a2323b331ae816d5b0633e68148e25d04, < 4cd378423a33194a773c267fc58606d28fce95cf	Fixed in 4cd378423a33194a773c267fc58606d28fce95cf
LinuxLinux	Affected ≥ a3c90f7a2323b331ae816d5b0633e68148e25d04, < 1d27214fd9a4d2c0c6d998fc9d4fb61448a3438e	Fixed in 1d27214fd9a4d2c0c6d998fc9d4fb61448a3438e
LinuxLinux	Affected =4.16	Fixed in–

Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: nft_flow_offload: drop flowtable reference on init error path nft_flow_offload_init() bumps the flowtable use count with nft_use_inc() before calling nf_ct_netns_get(). When the latter fails, the error is returned as-is and the reference is leaked. The upper layers do not balance it either: nf_tables_newexpr() clears expr->ops when the expression init callback fails, so the nft_expr_more() iteration in nft_rule_expr_deactivate() and nf_tables_rule_destroy() stops right before the failed expression and its ->destroy callback, which would drop the reference, never runs. Each failed rule addition therefore leaks one flowtable reference and the flowtable can no longer be removed: NFT_MSG_DELFLOWTABLE keeps reporting -EBUSY even though no rule references it. Save the nf_ct_netns_get() return value and undo the nft_use_inc() when it fails, restoring the inc/dec pairing within nft_flow_offload_init() itself.

References

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