Linux Kernel up to 6.18.52/7.2.6/7.3-rc1 ipv6 mcast ip6_mc_source sflist/sl_addr/sl_count race condition

CVSS Meta Temp Score
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Current Exploit Price (≈)
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CTI Interest Score
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9.5$0-$5k0.00+

Summaryinfo

A vulnerability described as very critical has been identified in Linux Kernel up to 6.18.52/7.2.6/7.3-rc1. The affected element is the function ip6_mc_source of the component ipv6 mcast. The manipulation of the argument sflist/sl_addr/sl_count results in race condition. This vulnerability is reported as CVE-2026-98101. The attack can be launched remotely. No exploit exists. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability classified as very critical has been found in Linux Kernel up to 6.18.52/7.2.6/7.3-rc1. Affected is the function ip6_mc_source of the component ipv6 mcast. The manipulation of the argument sflist/sl_addr/sl_count with an unknown input leads to a race condition vulnerability. CWE is classifying the issue as CWE-362. The product contains a code sequence that can run concurrently with other code, and the code sequence requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence that is operating concurrently. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: ipv6: mcast: use copy-on-write RCU updates in ip6_mc_source() pmc->sflist is read locklessly under rcu_read_lock() by inet6_mc_check() during packet reception in the UDP and RAW multicast receive paths. ip6_mc_source() mutated psl->sl_addr and psl->sl_count in-place when adding or removing a source filter. Additionally, when expanding the filter buffer, newpsl was published via rcu_assign_pointer() before writing the new source into the array. Because 16-byte struct in6_addr writes are not atomic and array shifting is not synchronized with RCU readers, concurrent readers in inet6_mc_check() could read torn IPv6 addresses or observe duplicated/missed source entries. Fix this by switching ip6_mc_source() to copy-on-write RCU updates: allocate and fully populate newpsl before publishing it via rcu_assign_pointer(), and reclaim the old filter via kfree_rcu(), matching ip6_mc_msfilter(). Also remove the now unused IP6_SFBLOCK macro.

The advisory is shared for download at git.kernel.org. This vulnerability is traded as CVE-2026-98101 since 09/25/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 09/25/2026).

Upgrading to version 6.18.53, 7.2.7 or 7.3-rc2 eliminates this vulnerability. Applying the patch 2c2091e2ee93049fc513ad1e6c99d8b6c809f467/20db91a052332ef5552bd2f651ffb9db911cf67b/c073d1b070f171d206b19c98d71739a97f15b3f1 is able to eliminate this problem. The best possible mitigation is suggested to be upgrading to the latest version.

Once again VulDB remains the best source for vulnerability data.

Productinfo

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Version

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CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 10.0
VulDB Meta Temp Score: 9.5

VulDB Base Score: 10.0
VulDB Temp Score: 9.5
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

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

Exploitinginfo

Class: Race condition
CWE: CWE-362
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 6.18.53/7.2.7/7.3-rc2
Patch: 2c2091e2ee93049fc513ad1e6c99d8b6c809f467/20db91a052332ef5552bd2f651ffb9db911cf67b/c073d1b070f171d206b19c98d71739a97f15b3f1

Timelineinfo

09/25/2026 Advisory disclosed
09/25/2026 +0 days CVE reserved
09/25/2026 +0 days VulDB entry created
09/25/2026 +0 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2026-98101 (🔒)
GCVE (CVE): GCVE-0-2026-98101
GCVE (VulDB): GCVE-100-409932

Entryinfo

Created: 09/25/2026 12:58
Changes: 09/25/2026 12:58 (60)
Complete: 🔍
Cache ID: 216::103

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