Linux Kernel up to 7.1.8 ipv4 fib_nlmsg_size/fib_nexthop_info buffer size

CVSS Meta Temp Score
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CTI Interest Score
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7.2$0-$5k0.00

Summaryinfo

A vulnerability has been found in Linux Kernel up to 7.1.8 and classified as critical. Affected by this issue is the function fib_nlmsg_size/fib_nexthop_info of the component ipv4. The manipulation leads to buffer size. This vulnerability is traded as CVE-2026-74657. It is possible to initiate the attack remotely. There is no exploit available. The affected component should be upgraded.

Detailsinfo

A vulnerability was found in Linux Kernel up to 7.1.8 and classified as critical. This issue affects the function fib_nlmsg_size/fib_nexthop_info of the component ipv4. The manipulation with an unknown input leads to a buffer size vulnerability. Using CWE to declare the problem leads to CWE-131. The product does not correctly calculate the size to be used when allocating a buffer, which could lead to a buffer overflow. Impacted is availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: ipv4: Fix fib_nlmsg_size() for RTA_VIA nexthops fib_nlmsg_size() still estimates nexthop space as if every gateway is encoded as an IPv4 RTA_GATEWAY attribute. IPv4 routes can also carry an IPv6 gateway, which fib_nexthop_info() dumps as RTA_VIA. As a result, route notifications can allocate an skb that is too small. fib_dump_info() then fails with -EMSGSIZE and rtmsg_fib() hits the WARN_ON() that marks such failures as a fib_nlmsg_size() bug. With panic_on_warn set, this becomes a kernel panic. Mirror the actual nexthop dump layout in fib_nlmsg_size(): account for IPv6 nexthop gateways dumped as RTA_VIA, for the no-header rtnexthop layout used inside RTA_MULTIPATH, and for RTA_FLOW only when it is actually present.

It is possible to read the advisory at git.kernel.org. The identification of this vulnerability is CVE-2026-74657 since 08/15/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 09/07/2026).

The vulnerability scanner Nessus provides a plugin with the ID 343049 (Oracle Linux 10 / 9 : Unbreakable Enterprise kernel (ELSA-2026-500248)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 5.15.216, 6.1.183, 6.6.152, 6.12.104, 6.18.45 or 7.1.9 eliminates this vulnerability. Applying the patch 0f0ca602941d0a81ae9514943ca06c55159c6385/5307a53599fa762c06e475ee4a375252074fd324/7f80ad373ce4a7af5367ff273cea0f16e91387f3/4a5dfbae5179f6574695012a980476254df2d295/a59edda6eda1252340354322d8ab318b2e9052fb/9b22f13524fa0de0d963bbd3002df6c28bae3395/4ff9548d84945d2cbf9e4c207288063a200ea397 is able to eliminate this problem. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at Tenable (343049). Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

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CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 7.5
VulDB Meta Temp Score: 7.2

VulDB Base Score: 7.5
VulDB Temp Score: 7.2
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AVACAuCIA
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Buffer size
CWE: CWE-131 / CWE-120 / CWE-119
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 343049
Nessus Name: Oracle Linux 10 / 9 : Unbreakable Enterprise kernel (ELSA-2026-500248)

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 5.15.216/6.1.183/6.6.152/6.12.104/6.18.45/7.1.9
Patch: 0f0ca602941d0a81ae9514943ca06c55159c6385/5307a53599fa762c06e475ee4a375252074fd324/7f80ad373ce4a7af5367ff273cea0f16e91387f3/4a5dfbae5179f6574695012a980476254df2d295/a59edda6eda1252340354322d8ab318b2e9052fb/9b22f13524fa0de0d963bbd3002df6c28bae3395/4ff9548d84945d2cbf9e4c207288063a200ea397

Timelineinfo

08/15/2026 CVE reserved
08/22/2026 +7 days Advisory disclosed
08/22/2026 +0 days VulDB entry created
09/07/2026 +16 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2026-74657 (🔒)
GCVE (CVE): GCVE-0-2026-74657
GCVE (VulDB): GCVE-100-394439

Entryinfo

Created: 08/22/2026 18:41
Updated: 09/07/2026 06:35
Changes: 08/22/2026 18:41 (59), 09/07/2026 06:35 (2)
Complete: 🔍
Cache ID: 216::103

Be aware that VulDB is the high quality source for vulnerability data.

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