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CVE.org (no NVD analysis yet)· CNA Linux

CVE-2026-98432: ipv4: free inet_opt and ireq_opt after an RCU grace period

CriticalCVSS 9.8 · v3.1—Proof of concept Fix available

Noroxi assessment

Priority: Monitor (action score 39/100)

  • Public proof-of-concept code exists (GitHub); there is no record of exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.76% (FIRST EPSS); higher than 55.7% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: Linux Linux 11a03ce3c4a62d84c10ccdfe47f8075006498568, 26d4c36d318cffbbd160884a0e4cec0da4da4936, 742f73df544e03744f2981c467d6542fe8172a2a; azl3 kernel 6.6.157.1-1 on Azure Linux 3.0 6.6.159.1-1.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 11a03ce3c4a62d84c10ccdfe47f8075006498568, 26d4c36d318cffbbd160884a0e4cec0da4da4936, 742f73df544e03744f2981c467d6542fe8172a2a; azl3 kernel 6.6.157.1-1 on Azure Linux 3.0 6.6.159.1-1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

In the Linux kernel, the following vulnerability has been resolved: ipv4: free inet_opt and ireq_opt after an RCU grace period tcp_v4_syn_recv_sock() transfers ownership of ireq->ireq_opt to the child socket (newinet->inet_opt) without copying it. Another cpu can concurrently process a retransmitted SYN for the same request socket, and send a SYNACK from tcp_check_req(). tcp_v4_send_synack() and inet_csk_route_req() read ireq->ireq_opt under rcu_read_lock() only, and ip_build_and_send_pkt() and ip_options_build() then read opt->optlen twice. Note that the SYNACK timer itself is not an issue: it holds a reference on its request socket, and inet_csk_reqsk_queue_drop() calls timer_delete_sync() before the child can be freed. Since commit 079096f103fa ("tcp/dccp: install syn_recv requests into ehash table"), request sockets are processed without holding the listener lock, so nothing prevents the child socket from being freed while the SYNACK is still being built. TCP child sockets do not have SOCK_RCU_FREE, and inet_sock_destruct() frees inet_opt with a plain kfree(), leading to a use-after-free in ip_options_build(). A similar issue exists with request socket migration (net.ipv4.tcp_migrate_req=1, or a BPF_SK_REUSEPORT_SELECT_OR_MIGRATE program). reqsk_timer_handler() clones the request socket with inet_reqsk_clone(), so that the old request socket and its clone share the same ireq_opt, then reqsk_migrate_reset() clears the pointer in the old one. Another cpu holding a reference on the old request socket can still be using these options (sending a SYNACK, or creating a child in tcp_v4_syn_recv_sock()) when the clone is freed, and tcp_v4_reqsk_destructor() also uses a plain kfree(). Readers already use RCU, and other paths replacing inet_opt (do_ip_setsockopt(), cipso_v4_sock_setattr()...) already use kfree_rcu(). Use kfree_rcu() in inet_sock_destruct() and tcp_v4_reqsk_destructor() as well. IPv6 is not affected by the first issue, because tcp_v6_syn_recv_sock() duplicates the options. tcp_v6_reqsk_destructor() has the same migration issue with ipv6_opt, which is only set by CALIPSO. This will be addressed in a separate patch.

Published
Oct 15, 2026
Updated
Nov 12, 2026
EPSS
0.7% · 55th percentile

Report tools

JSON

Action score

39

Monitor

Low priority for now.

CVSS
39 / 40 · 9.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.7%

CNA vs NVD score

NVD
—
CNA · Linux
9.8
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

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  • Not in KEV: no record of exploitation in the wild
  • Proof of concept exists, no weaponized module
  • A fix has been released

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
linuxlinux kernel

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

    • 4.4affected
    • 079096f103faca2dd87342cca6f23d4b34da8871 and later · before b3b027ef0cd322bfa839b9aaf5b27551eea54cf6affected · git
    • 079096f103faca2dd87342cca6f23d4b34da8871 and later · before 95a8c8fa9f27dce64c40c41c062de7728bf34ab5affected · git
    • 079096f103faca2dd87342cca6f23d4b34da8871 and later · before 89b5b1eb7d633c33832b7ff2c02e19a144705036affected · git
    • 079096f103faca2dd87342cca6f23d4b34da8871 and later · before 742f73df544e03744f2981c467d6542fe8172a2aaffected · git
    • 079096f103faca2dd87342cca6f23d4b34da8871 and later · before 11a03ce3c4a62d84c10ccdfe47f8075006498568affected · git
    • 079096f103faca2dd87342cca6f23d4b34da8871 and later · before a47406c769f72c070386985488f1c4d057df86b2affected · git
    • 079096f103faca2dd87342cca6f23d4b34da8871 and later · before 26d4c36d318cffbbd160884a0e4cec0da4da4936affected · git
    • 079096f103faca2dd87342cca6f23d4b34da8871 and later · before e3f33b0a1d89d738e2b913dab519226eaf76e15baffected · git
    • before 4.4not affected · semver
Affected versions · NVD (8)

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • linux linux kernel4.4 and later · before 5.10.272
  • linux linux kernel5.11 and later · before 5.15.223
  • linux linux kernel5.16 and later · before 6.1.190
  • linux linux kernel6.2 and later · before 6.6.159
  • linux linux kernel6.7 and later · before 6.12.113
  • linux linux kernel6.13 and later · before 6.18.56
  • linux linux kernel6.19 and later · before 7.2.10
  • linux linux kernel7.3

Package-level exposure

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

EcosystemPackageAffected rangeFix
AlmaLinux:10kernelbefore 6.12.0-211.72.1.el10_26.12.0-211.72.1.el10_2
AlmaLinux:10kernel-64kbefore 6.12.0-211.72.1.el10_26.12.0-211.72.1.el10_2
AlmaLinux:10kernel-64k-corebefore 6.12.0-211.72.1.el10_26.12.0-211.72.1.el10_2
AlmaLinux:10kernel-64k-debugbefore 6.12.0-211.72.1.el10_26.12.0-211.72.1.el10_2
AlmaLinux:10kernel-64k-debug-corebefore 6.12.0-211.72.1.el10_26.12.0-211.72.1.el10_2
AlmaLinux:10kernel-64k-debug-develbefore 6.12.0-211.72.1.el10_26.12.0-211.72.1.el10_2
AlmaLinux:10kernel-64k-debug-devel-matchedbefore 6.12.0-211.72.1.el10_26.12.0-211.72.1.el10_2
AlmaLinux:10kernel-64k-debug-modulesbefore 6.12.0-211.72.1.el10_26.12.0-211.72.1.el10_2
AlmaLinux:10kernel-64k-debug-modules-corebefore 6.12.0-211.72.1.el10_26.12.0-211.72.1.el10_2
AlmaLinux:10kernel-64k-debug-modules-extrabefore 6.12.0-211.72.1.el10_26.12.0-211.72.1.el10_2
AlmaLinux:10kernel-64k-develbefore 6.12.0-211.72.1.el10_26.12.0-211.72.1.el10_2
AlmaLinux:10kernel-64k-devel-matchedbefore 6.12.0-211.72.1.el10_26.12.0-211.72.1.el10_2
AlmaLinux:10kernel-64k-modulesbefore 6.12.0-211.72.1.el10_26.12.0-211.72.1.el10_2
AlmaLinux:10kernel-64k-modules-corebefore 6.12.0-211.72.1.el10_26.12.0-211.72.1.el10_2
AlmaLinux:10kernel-64k-modules-extrabefore 6.12.0-211.72.1.el10_26.12.0-211.72.1.el10_2
AlmaLinux:10kernel-abi-stablelistsbefore 6.12.0-211.72.1.el10_26.12.0-211.72.1.el10_2
AlmaLinux:10kernel-corebefore 6.12.0-211.72.1.el10_26.12.0-211.72.1.el10_2
AlmaLinux:10kernel-cross-headersbefore 6.12.0-211.72.1.el10_26.12.0-211.72.1.el10_2
AlmaLinux:10kernel-debugbefore 6.12.0-211.72.1.el10_26.12.0-211.72.1.el10_2
AlmaLinux:10kernel-debug-corebefore 6.12.0-211.72.1.el10_26.12.0-211.72.1.el10_2
AlmaLinux:10kernel-debug-develbefore 6.12.0-211.72.1.el10_26.12.0-211.72.1.el10_2
AlmaLinux:10kernel-debug-devel-matchedbefore 6.12.0-211.72.1.el10_26.12.0-211.72.1.el10_2
AlmaLinux:10kernel-debug-modulesbefore 6.12.0-211.72.1.el10_26.12.0-211.72.1.el10_2
AlmaLinux:10kernel-debug-modules-corebefore 6.12.0-211.72.1.el10_26.12.0-211.72.1.el10_2

+96

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV
    90Now
  • CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe…KEV
    89Now
  • CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV
    85Now

Published before and after this one in the same product

  • ← EarlierCVE-2026-98162Sep 25, 2026 · smb/server: fix tree connection leak in smb2_tree_connect()
    22Monitor
  • ← EarlierCVE-2026-98163Sep 26, 2026 · cgroup: Avoid iteration of dying tasks with zero refcount
    28Monitor
  • ← EarlierCVE-2026-98164Sep 29, 2026 · KVM: x86/mmu: Check write tracking in all address spaces
    22Monitor

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 Linux11a03ce3c4a62d84c10ccdfe47f8075006498568Vendor (CNA)
Linux Linux26d4c36d318cffbbd160884a0e4cec0da4da4936Vendor (CNA)
Linux Linux742f73df544e03744f2981c467d6542fe8172a2aVendor (CNA)
Linux Linux89b5b1eb7d633c33832b7ff2c02e19a144705036Vendor (CNA)
Linux Linux95a8c8fa9f27dce64c40c41c062de7728bf34ab5Vendor (CNA)
Linux Linuxa47406c769f72c070386985488f1c4d057df86b2Vendor (CNA)
Linux Linuxb3b027ef0cd322bfa839b9aaf5b27551eea54cf6Vendor (CNA)
Linux Linuxe3f33b0a1d89d738e2b913dab519226eaf76e15bVendor (CNA)
azl3 kernel 6.6.157.1-1 on Azure Linux 3.06.6.159.1-1 · Release NotesMicrosoft (MSRC)
almalinux:bpftool4.18.0-553.182.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel4.18.0-553.182.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel5.14.0-687.64.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k5.14.0-687.64.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-core5.14.0-687.64.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug5.14.0-687.64.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-core5.14.0-687.64.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-devel5.14.0-687.64.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-devel-matched5.14.0-687.64.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-modules5.14.0-687.64.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-modules-core5.14.0-687.64.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-modules-extra5.14.0-687.64.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-devel5.14.0-687.64.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-devel-matched5.14.0-687.64.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-abi-stablelists4.18.0-553.182.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-core4.18.0-553.182.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-cross-headers4.18.0-553.182.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug4.18.0-553.182.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug-core4.18.0-553.182.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug-devel4.18.0-553.182.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug-modules4.18.0-553.182.1.el8_10 · AlmaLinux:8Package registry (OSV)

+34

Exploit status

Proof of concept available

A public proof of concept or detection signature exists. Exploit knowledge is out there; don't delay patching.

Evidence

  • Proof-of-concept repository on GitHub ×50

Noroxi does not host or link to exploit code. Metasploit module names and Nuclei template ids are shown (names, not code); Exploit-DB entries and PoC repositories are given as counts only.

Public exploit evidence
SourceKindDate
Proof-of-concept repository on GitHub50 repositories2026-09-26 → 2026-11-02

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

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

  1. First PoC-20 d
  2. Published
  3. Fix recordedsame day
  4. TodayNov 13, 2026+29 d
EPSS, last 120 days+1% in 7 days

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

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Not on record for this CVE: patch commit or PR link · researcher credit · variant or chain candidate · public bounty program.

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

CWE-416 · Use After Free

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

nvd-secondary

Root cause

After a memory region is freed, another reference pointing to it is still used. By then, the same region may have been allocated for different data.

The bug in code

The whole CWE-416 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

c
free(dev->buf);/* ... another thread is still running ... */process(dev->buf);

Fixed

c
lock(&dev->lock);free(dev->buf);dev->buf = NULL;unlock(&dev->lock);

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Exploit maturitynone → poc
  2. CVSS— → 9.8
  3. Severity— → critical
  4. Exploit maturity— → none
  5. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (11 more)

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

All records