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NVD / CVE Program· CNA Linux

CVE-2026-64523: net/handshake: Take a long-lived file reference at submit

Noroxi assessment

Priority: Monitor (action score 39/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.45% (FIRST EPSS).
  • 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.
  • According to CISA the attack is automatable: targets can be found by mass scanning.
  • Fixed version: Linux Linux 09dba37eee70d0596e26645015f1aa95a9848e9d, 16eaba5aa89c04eea125905bb8f988c1897f4f29, 22e371a93563c30ebebc576db049785e0d7fc617; azl3 kernel 6.6.152.1-1 on Azure Linux 3.0 Release Notes; azl3 kernel 6.6.157.1-1 on Azure Linux 3.0 Release Notes.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 09dba37eee70d0596e26645015f1aa95a9848e9d, 16eaba5aa89c04eea125905bb8f988c1897f4f29, 22e371a93563c30ebebc576db049785e0d7fc617; azl3 kernel 6.6.152.1-1 on Azure Linux 3.0 Release Notes; azl3 kernel 6.6.157.1-1 on Azure Linux 3.0 Release Notes 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: net/handshake: Take a long-lived file reference at submit handshake_nl_accept_doit() needs the file pointer backing req->hr_sk->sk_socket to survive the window between handshake_req_next() and the subsequent FD_PREPARE() and get_file(). The submit-side sock_hold() does not provide that. sk_refcnt keeps struct sock alive, but struct socket is owned by sock->file: when the consumer fputs the last file reference, sock_release() tears the socket down regardless of any sock_hold. Add an hr_file pointer to struct handshake_req and acquire an explicit reference on sock->file during handshake_req_submit(). handshake_complete() and handshake_req_cancel() release the reference on the completion-bit-winning path. The submit error path must also release the file reference, but after rhashtable insertion a concurrent handshake_req_cancel() can discover the request and race the error path. Gate the error-path cleanup -- sk_destruct restoration, fput, and request destruction -- with test_and_set_bit(HANDSHAKE_F_REQ_COMPLETED), the same serialization handshake_complete() and handshake_req_cancel() already use. When cancel has already claimed ownership, the submit error path returns without touching the request; socket teardown handles final destruction. The accept-side dereferences are not yet retargeted; that change comes in the next patch.

CriticalCVSS 9.8 · v3.1—No exploit Fix available
Published
Jul 25, 2026
Updated
Nov 3, 2026
EPSS
0.4% · 39th 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 · 0.4%

CISA SSVC decision

Exploitation
none
Automatable
yes
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

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.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

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When you'll hear from us

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  • when exploit code appears or is weaponized
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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.

—

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

    • 6.4affected
    • 3b3009ea8abb713b022d94fba95ec270cf6e7eae and later · before 22e371a93563c30ebebc576db049785e0d7fc617affected · git
    • 3b3009ea8abb713b022d94fba95ec270cf6e7eae and later · before 685b10dd0e32c7782cead16c8cf055c609678583affected · git
    • 3b3009ea8abb713b022d94fba95ec270cf6e7eae and later · before b913801ad9b9a51437d84d030ec6843e08976bd6affected · git
    • 3b3009ea8abb713b022d94fba95ec270cf6e7eae and later · before 16eaba5aa89c04eea125905bb8f988c1897f4f29affected · git
    • 3b3009ea8abb713b022d94fba95ec270cf6e7eae and later · before 09dba37eee70d0596e26645015f1aa95a9848e9daffected · git
    • before 6.4not affected · semver
    • 6.6.160 and later · up to and including 6.6.*not affected · semver
    • 6.12.93 and later · up to and including 6.12.*not affected · semver
    • 6.18.44 and later · up to and including 6.18.*not affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
AlmaLinux:10kernelbefore 6.12.0-211.69.1.el10_26.12.0-211.69.1.el10_2
AlmaLinux:10kernel-64kbefore 6.12.0-211.69.1.el10_26.12.0-211.69.1.el10_2
AlmaLinux:10kernel-64k-corebefore 6.12.0-211.69.1.el10_26.12.0-211.69.1.el10_2
AlmaLinux:10kernel-64k-debugbefore 6.12.0-211.69.1.el10_26.12.0-211.69.1.el10_2
AlmaLinux:10kernel-64k-debug-corebefore 6.12.0-211.69.1.el10_26.12.0-211.69.1.el10_2
AlmaLinux:10kernel-64k-debug-develbefore 6.12.0-211.69.1.el10_26.12.0-211.69.1.el10_2
AlmaLinux:10kernel-64k-debug-devel-matchedbefore 6.12.0-211.69.1.el10_26.12.0-211.69.1.el10_2
AlmaLinux:10kernel-64k-debug-modulesbefore 6.12.0-211.69.1.el10_26.12.0-211.69.1.el10_2
AlmaLinux:10kernel-64k-debug-modules-corebefore 6.12.0-211.69.1.el10_26.12.0-211.69.1.el10_2
AlmaLinux:10kernel-64k-debug-modules-extrabefore 6.12.0-211.69.1.el10_26.12.0-211.69.1.el10_2
AlmaLinux:10kernel-64k-develbefore 6.12.0-211.69.1.el10_26.12.0-211.69.1.el10_2
AlmaLinux:10kernel-64k-devel-matchedbefore 6.12.0-211.69.1.el10_26.12.0-211.69.1.el10_2
AlmaLinux:10kernel-64k-modulesbefore 6.12.0-211.69.1.el10_26.12.0-211.69.1.el10_2
AlmaLinux:10kernel-64k-modules-corebefore 6.12.0-211.69.1.el10_26.12.0-211.69.1.el10_2
AlmaLinux:10kernel-64k-modules-extrabefore 6.12.0-211.69.1.el10_26.12.0-211.69.1.el10_2
AlmaLinux:10kernel-abi-stablelistsbefore 6.12.0-211.69.1.el10_26.12.0-211.69.1.el10_2
AlmaLinux:10kernel-corebefore 6.12.0-211.69.1.el10_26.12.0-211.69.1.el10_2
AlmaLinux:10kernel-cross-headersbefore 6.12.0-211.69.1.el10_26.12.0-211.69.1.el10_2
AlmaLinux:10kernel-debugbefore 6.12.0-211.69.1.el10_26.12.0-211.69.1.el10_2
AlmaLinux:10kernel-debug-corebefore 6.12.0-211.69.1.el10_26.12.0-211.69.1.el10_2
AlmaLinux:10kernel-debug-develbefore 6.12.0-211.69.1.el10_26.12.0-211.69.1.el10_2
AlmaLinux:10kernel-debug-devel-matchedbefore 6.12.0-211.69.1.el10_26.12.0-211.69.1.el10_2
AlmaLinux:10kernel-debug-modulesbefore 6.12.0-211.69.1.el10_26.12.0-211.69.1.el10_2
AlmaLinux:10kernel-debug-modules-corebefore 6.12.0-211.69.1.el10_26.12.0-211.69.1.el10_2

+96

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

Published before and after this one in the same product

  • ← EarlierCVE-2026-64521Jul 25, 2026 · pinctrl: meson: amlogic-a4: fix deadlock issue
    0Monitor
  • ← EarlierCVE-2026-64522Jul 25, 2026 · net/mlx5e: Fix eswitch mode block underflow on IPsec acquire SA
    35Monitor
  • Later →CVE-2026-64524Jul 25, 2026 · drm/hyperv: validate resolution_count and fix WIN8 fallback
    30Monitor

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 Linux09dba37eee70d0596e26645015f1aa95a9848e9dVendor (CNA)
Linux Linux16eaba5aa89c04eea125905bb8f988c1897f4f29Vendor (CNA)
Linux Linux22e371a93563c30ebebc576db049785e0d7fc617Vendor (CNA)
Linux Linux685b10dd0e32c7782cead16c8cf055c609678583Vendor (CNA)
Linux Linuxb913801ad9b9a51437d84d030ec6843e08976bd6Vendor (CNA)
azl3 kernel 6.6.152.1-1 on Azure Linux 3.0Release NotesMicrosoft (MSRC)
azl3 kernel 6.6.157.1-1 on Azure Linux 3.0Release NotesMicrosoft (MSRC)
almalinux:kernel5.14.0-687.61.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k5.14.0-687.61.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-core5.14.0-687.61.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug5.14.0-687.61.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-core5.14.0-687.61.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-devel5.14.0-687.61.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-devel-matched5.14.0-687.61.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-modules5.14.0-687.61.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-modules-core5.14.0-687.61.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-modules-extra5.14.0-687.61.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-devel5.14.0-687.61.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-devel-matched5.14.0-687.61.1.el9_8 · AlmaLinux:9Package registry (OSV)
debian:linux6.12.94-1 · Debian:13Package registry (OSV)
rocky linux:kernel0:5.14.0-687.61.1.el9_8 · Rocky Linux:9Package 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

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

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.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

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.

  • CVE-2026-645301 days apartnet/sched: cls_api: Handle TC_ACT_CONSUMED in tcf_qevent_handle
    39Monitor
  • CVE-2026-645412 days apartnet/smc: fix UAF in smc_cdc_rx_handler() by pinning the socket
    39Monitor
  • CVE-2026-639796 days apartnet/handshake: hand off the pinned file reference to accept_doit
    39Monitor
  • CVE-2026-6456410 days apartsctp: don't free the ASCONF's own transport in DEL-IP processing
    39Monitor
  • CVE-2026-6811716 days aparttipc: clear sock->sk on the failed-insert path in tipc_sk_create()
    39Monitor
  • CVE-2026-6815616 days apartlibceph: refresh auth->authorizer_buf{,_len} after authorizer update
    39Monitor

Chain candidates

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

—

Bug bounty scope

No known public program.

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

National notice (Türkiye Cybersecurity Directorate / USOM)

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

All national notices →

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. SSVC exploitation— → none
  2. Fix✗ → ✓

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

References

Show all references (4 more)

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

All records