Linux Kernel up to 6.19.11 net /proc/net/ip6_flowlabel ip6fl_seq_show denial of service

CVSS Meta Temp Score
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CTI Interest Score
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6.7$0-$5k0.00

Summaryinfo

A vulnerability identified as critical has been detected in Linux Kernel up to 6.19.11. The affected element is the function ip6fl_seq_show of the file /proc/net/ip6_flowlabel of the component net. The manipulation leads to denial of service. This vulnerability is referenced as CVE-2026-31680. Remote exploitation of the attack is possible. No exploit is available. You should upgrade the affected component.

Detailsinfo

A vulnerability was found in Linux Kernel up to 6.19.11. It has been rated as critical. This issue affects the function ip6fl_seq_show of the file /proc/net/ip6_flowlabel of the component net. The manipulation with an unknown input leads to a denial of service vulnerability. Using CWE to declare the problem leads to CWE-404. The product does not release or incorrectly releases a resource before it is made available for re-use. Impacted is availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: net: ipv6: flowlabel: defer exclusive option free until RCU teardown `ip6fl_seq_show()` walks the global flowlabel hash under the seq-file RCU read-side lock and prints `fl->opt->opt_nflen` when an option block is present. Exclusive flowlabels currently free `fl->opt` as soon as `fl->users` drops to zero in `fl_release()`. However, the surrounding `struct ip6_flowlabel` remains visible in the global hash table until later garbage collection removes it and `fl_free_rcu()` finally tears it down. A concurrent `/proc/net/ip6_flowlabel` reader can therefore race that early `kfree()` and dereference freed option state, triggering a crash in `ip6fl_seq_show()`. Fix this by keeping `fl->opt` alive until `fl_free_rcu()`. That matches the lifetime already required for the enclosing flowlabel while readers can still reach it under RCU.

The advisory is shared at git.kernel.org. The identification of this vulnerability is CVE-2026-31680 since 03/09/2026. The exploitation is known to be difficult. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details are known, but no exploit is available. MITRE ATT&CK project uses the attack technique T1499 for this issue.

The vulnerability scanner Nessus provides a plugin with the ID 310344 (Linux Distros Unpatched Vulnerability : CVE-2026-31680), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 5.10.253, 5.15.203, 6.1.168, 6.6.134, 6.12.81, 6.18.22 or 6.19.12 eliminates this vulnerability. Applying the patch 4b6798024f7b2d535f3db1002c760143cdbd1bd3/3c54b66c83fb8fcbde8e6a7bf90b65856e39f827/5a6b15f861b7c1304949e3350d23490a5fe429fd/6c7fbdb8ffde6413640de7cfbd7c976c353e89f8/8027964931785cb73d520ac70a342a3dc16c249b/414726b69921fe6355ae453f5b35e68dd078342a/572ce62778519a7d4d1c15f55dd2e45a474133c4/9ca562bb8e66978b53028fa32b1a190708e6a091 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (310344) and EUVD (EUVD-2026-25647). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

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CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 6.8
VulDB Meta Temp Score: 6.7

VulDB Base Score: 5.9
VulDB Temp Score: 5.7
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 7.8
CNA Vector (Linux): 🔒

CVSSv2info

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

Exploitinginfo

Class: Denial of service
CWE: CWE-404
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 310344
Nessus Name: Linux Distros Unpatched Vulnerability : CVE-2026-31680

Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 5.10.253/5.15.203/6.1.168/6.6.134/6.12.81/6.18.22/6.19.12
Patch: 4b6798024f7b2d535f3db1002c760143cdbd1bd3/3c54b66c83fb8fcbde8e6a7bf90b65856e39f827/5a6b15f861b7c1304949e3350d23490a5fe429fd/6c7fbdb8ffde6413640de7cfbd7c976c353e89f8/8027964931785cb73d520ac70a342a3dc16c249b/414726b69921fe6355ae453f5b35e68dd078342a/572ce62778519a7d4d1c15f55dd2e45a474133c4/9ca562bb8e66978b53028fa32b1a190708e6a091

Timelineinfo

03/09/2026 CVE reserved
04/25/2026 +46 days Advisory disclosed
04/25/2026 +0 days VulDB entry created
07/17/2026 +83 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2026-31680 (🔒)
GCVE (CVE): GCVE-0-2026-31680
GCVE (VulDB): GCVE-100-359585
EUVD: 🔒

Entryinfo

Created: 04/25/2026 11:34
Updated: 07/17/2026 10:42
Changes: 04/25/2026 11:34 (60), 04/25/2026 13:02 (1), 04/26/2026 05:51 (2), 07/17/2026 10:42 (11)
Complete: 🔍
Cache ID: 216::103

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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