VulnerabilityPublished 22 Aug 2026Updated 6 Nov 2026

CVE-2026-74657: Linux kernel · ipv4: Fix fib_nlmsg_size() for RTA_VIA nexthops

Affects Linux kernelSource CVE Database V5

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Not known to be exploited · fixed in a59edda6eda1252340354322d8ab318b2e9052fb : patch Linux kernel soon.

Data as of 6 Nov 2026, 17:48 UTC

Severity

High

Rated High by Threat Radar's AI analysis · CVSS not yet scored by NVD

Thin evidence

One scorer or none

Exploitation: No evidence of active exploitation and no public proof of concept
Automatable: Attackers cannot reliably automate steps 1–4 of the kill chain
Technical impact: Limited control over the software or limited information exposure

CISA SSVC assessment, 2026-11-06.

Patch

Available – fixed in a59edda6eda1252340354322d8ab318b2e9052fb, 57195f0ab5cfbb5ee0864e5aff15ceb48f5a5e28, 5307a53599fa762c06e475ee4a375252074fd324 +5

Exploitation evidence

Disclosed: evidence found.
CVE published 22 Aug 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: 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 6 Nov 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.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), 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 ≥ d15662682db232da77136cd348f4c9df312ca6f9, < a59edda6eda1252340354322d8ab318b2e9052fb	Fixed in a59edda6eda1252340354322d8ab318b2e9052fb
LinuxLinux	Affected ≥ d15662682db232da77136cd348f4c9df312ca6f9, < 57195f0ab5cfbb5ee0864e5aff15ceb48f5a5e28	Fixed in 57195f0ab5cfbb5ee0864e5aff15ceb48f5a5e28
LinuxLinux	Affected ≥ d15662682db232da77136cd348f4c9df312ca6f9, < 5307a53599fa762c06e475ee4a375252074fd324	Fixed in 5307a53599fa762c06e475ee4a375252074fd324
LinuxLinux	Affected ≥ d15662682db232da77136cd348f4c9df312ca6f9, < 9b22f13524fa0de0d963bbd3002df6c28bae3395	Fixed in 9b22f13524fa0de0d963bbd3002df6c28bae3395
LinuxLinux	Affected ≥ d15662682db232da77136cd348f4c9df312ca6f9, < 7f80ad373ce4a7af5367ff273cea0f16e91387f3	Fixed in 7f80ad373ce4a7af5367ff273cea0f16e91387f3
LinuxLinux	Affected ≥ d15662682db232da77136cd348f4c9df312ca6f9, < 4ff9548d84945d2cbf9e4c207288063a200ea397	Fixed in 4ff9548d84945d2cbf9e4c207288063a200ea397

AI-suggested

A fix is available in the Linux kernel as identified by the fixed commit versions. Users should update to a kernel version that includes these fixes to prevent kernel panics related to this issue.

Description

A vulnerability in the Linux kernel's IPv4 routing code was fixed to correctly calculate message sizes for route notifications involving IPv6 gateways. The flaw caused route notifications to allocate buffers that were too small, leading to failures and potentially kernel panics when panic_on_warn is enabled.

Impact

The vulnerability can cause kernel panics on systems with panic_on_warn enabled due to incorrect buffer size allocation for route notifications involving IPv6 gateways in IPv4 routes. This can lead to system instability or denial of service.

Summary

The Linux kernel's fib_nlmsg_size() function incorrectly estimated the size needed for route notification messages by assuming all gateways were IPv4 RTA_GATEWAY attributes. However, IPv4 routes can include IPv6 gateways encoded as RTA_VIA attributes. This mismatch caused the kernel to allocate insufficient buffer space, resulting in fib_dump_info() failing with -EMSGSIZE and triggering WARN_ON() in rtmsg_fib(). If panic_on_warn is set, this leads to a kernel panic. The fix updates fib_nlmsg_size() to accurately reflect the actual nexthop dump layout, accounting for IPv6 nexthop gateways, the no-header rtnexthop layout inside RTA_MULTIPATH, and conditional presence of RTA_FLOW.

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 6 Nov 2026, 17:48 UTC

Technical details

References

Community reviews

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