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CVE-2026-98103· NVD / CVE Program· CNA Linux

igmp: convert struct ip_sf_list to RCU

In the Linux kernel, the following vulnerability has been resolved: igmp: convert struct ip_sf_list to RCU Commit 23d2b94043ca ("igmp: Add ip_mc_list lock in ip_check_mc_rcu") added spin_lock_bh(&im->lock) to ip_check_mc_rcu() to prevent a use-after-free while iterating im->sources during concurrent deletions. However, ip_check_mc_rcu() is called from RCU read-side critical sections in packet receive and route lookup fast paths (e.g. __mkroute_output(), ip_route_input_rcu(), and __udp4_lib_rcv()). When igmpv3_send_cr() or igmpv3_send_report() holds &pmc->lock and calls add_grec() -> igmpv3_newpack() -> ip_route_output_ports(), an XFRM policy matching a multicast destination triggers xfrm_tmpl_resolve_one() -> xfrm4_get_saddr() -> __mkroute_output() -> ip_check_mc_rcu(). This attempts to acquire &im->lock while &pmc->lock is already held on the same CPU, triggering a lockdep recursive locking warning / deadlock. Fix this by converting IPv4 struct ip_sf_list to RCU, mirroring the IPv6 implementation in net/ipv6/mcast.c: 1. Add struct rcu_head to struct ip_sf_list and annotate sf_next, sources, and tomb as __rcu pointers. 2. Use rcu_assign_pointer() and kfree_rcu() for list updates and deletions. 3. Remove spin_lock_bh(&im->lock) from ip_check_mc_rcu() and traverse im->sources locklessly with for_each_psf_rcu(), reading and writing counter fields with READ_ONCE() and WRITE_ONCE(). Note: RCU conversion of /proc/net/mcfilter will be done in a separate patch.

—No exploit Fix available
Published
Sep 25, 2026
Updated
Sep 25, 2026
EPSS
0.2% · 5th percentile
CWE
—
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Action score

0

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Low priority for now.

CVSS
0 / 40 · —
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.2%

Affected systems

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Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • b24065948ae6c48c9e20891f8cfe9850f1d748be, e9924c4204ede999b0515fd31a370a1e27f676bc, 78967749984cf3614de346c90f3e259ff8272735, 4768973dffed4d0126854514335ed4fe87bec1ab, d84708451d9041dff8a81e3718f821f12d2eb6c5, ddd7e8b7b84836c584a284b98ca9bd7a348a0558, 961447ff60291b91e27d5c32fa549c1411ad3b70, d1a3c6d5925a8d00a32c5ef2d674dd9c0ce89c95, 5.15affected
    • 23d2b94043ca8835bd1e67749020e839f396a1c2 and later · before f5182dfad54277267a8cb0c004a9cd4cf35aeebbaffected · git
    • 23d2b94043ca8835bd1e67749020e839f396a1c2 and later · before d3011d1f293478c730aa0870490afa145c37600eaffected · git
    • 23d2b94043ca8835bd1e67749020e839f396a1c2 and later · before e3206419bdb04e2087d8cc6be324df8639b3fac5affected · git
    • 23d2b94043ca8835bd1e67749020e839f396a1c2 and later · before 2987ee196c88dbde0463dc87d5fb209c684e34a2affected · git
    • 4.4.284 and later · before 4.5affected · semver
    • 4.9.283 and later · before 4.10affected · semver
    • 4.14.247 and later · before 4.15affected · semver
    • 4.19.207 and later · before 4.20affected · semver
    • 5.4.145 and later · before 5.5affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxall versions—
Debian:13linuxbefore 6.12.111-16.12.111-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-74705udp: fix potential use-after-free in tunnel segmentation
    40Plan
  • CVE-2026-74612veth: fix skb length accounting after XDP frag adjustment
    40Plan
  • CVE-2026-74475vxlan: use neigh_ha_snapshot() in route_shortcircuit()
    40Plan
  • CVE-2026-74309vdpa/octeon_ep: fix IRQ-to-ring mapping in interrupt handler
    40Plan
  • CVE-2026-74280crypto: marvell/octeontx - fix DMA cleanup using wrong loop index
    40Plan
  • CVE-2026-74279crypto: cavium/cpt - fix DMA cleanup using wrong loop index
    40Plan

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux2987ee196c88dbde0463dc87d5fb209c684e34a2Vendor (CNA)
Linux Linux4.10Vendor (CNA)
Linux Linux4.15Vendor (CNA)
Linux Linux4.20Vendor (CNA)
Linux Linux4.5Vendor (CNA)
Linux Linux5.11Vendor (CNA)
Linux Linux5.14Vendor (CNA)
Linux Linux5.15Vendor (CNA)
Linux Linux5.5Vendor (CNA)
Linux Linuxd3011d1f293478c730aa0870490afa145c37600eVendor (CNA)
Linux Linuxe3206419bdb04e2087d8cc6be324df8639b3fac5Vendor (CNA)
Linux Linuxf5182dfad54277267a8cb0c004a9cd4cf35aeebbVendor (CNA)
azl3 kernel 6.6.157.1-1 on Azure Linux 3.0Release NotesMicrosoft (MSRC)
debian:linux6.12.111-1 · Debian:13Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

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No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

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No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

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Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

No CVSS vector for this record, so attack conditions can't be derived.

Weakness class (CWE)

—

Attack context

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Change log

  1. Fix✗ → ✓

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References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

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