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NVD / CVE Program· CNA Linux

CVE-2026-31503: udp: Fix wildcard bind conflict check when using hash2

Noroxi assessment

Priority: Monitor (action score 22/100)

  • 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: 0.12% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: Linux Linux 0a360f7f73a06ac88f18917055fbcc79694252d7, 18d84c45def3671d5c89fbdd5d4ab8a3217fe4b4, 2297e38114316b26ae02f2d205c49b5511c5ed55; azl3 kernel 6.6.130.1-3 on Azure Linux 3.0 6.6.134.1-2; cbl2 kernel 5.15.202.1-1 on CBL-Mariner 2.0 Release Notes.

Low priority for now. Upgrade to Linux Linux 0a360f7f73a06ac88f18917055fbcc79694252d7, 18d84c45def3671d5c89fbdd5d4ab8a3217fe4b4, 2297e38114316b26ae02f2d205c49b5511c5ed55; azl3 kernel 6.6.130.1-3 on Azure Linux 3.0 6.6.134.1-2; cbl2 kernel 5.15.202.1-1 on CBL-Mariner 2.0 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: udp: Fix wildcard bind conflict check when using hash2 When binding a udp_sock to a local address and port, UDP uses two hashes (udptable->hash and udptable->hash2) for collision detection. The current code switches to "hash2" when hslot->count > 10. "hash2" is keyed by local address and local port. "hash" is keyed by local port only. The issue can be shown in the following bind sequence (pseudo code): bind(fd1, "[fd00::1]:8888") bind(fd2, "[fd00::2]:8888") bind(fd3, "[fd00::3]:8888") bind(fd4, "[fd00::4]:8888") bind(fd5, "[fd00::5]:8888") bind(fd6, "[fd00::6]:8888") bind(fd7, "[fd00::7]:8888") bind(fd8, "[fd00::8]:8888") bind(fd9, "[fd00::9]:8888") bind(fd10, "[fd00::10]:8888") /* Correctly return -EADDRINUSE because "hash" is used * instead of "hash2". udp_lib_lport_inuse() detects the * conflict. */ bind(fail_fd, "[::]:8888") /* After one more socket is bound to "[fd00::11]:8888", * hslot->count exceeds 10 and "hash2" is used instead. */ bind(fd11, "[fd00::11]:8888") bind(fail_fd, "[::]:8888") /* succeeds unexpectedly */ The same issue applies to the IPv4 wildcard address "0.0.0.0" and the IPv4-mapped wildcard address "::ffff:0.0.0.0". For example, if there are existing sockets bound to "192.168.1.[1-11]:8888", then binding "0.0.0.0:8888" or "[::ffff:0.0.0.0]:8888" can also miss the conflict when hslot->count > 10. TCP inet_csk_get_port() already has the correct check in inet_use_bhash2_on_bind(). Rename it to inet_use_hash2_on_bind() and move it to inet_hashtables.h so udp.c can reuse it in this fix.

MediumCVSS 5.5 · v3.1—No exploit Fix available
Published
Apr 22, 2026
Updated
Oct 15, 2026
EPSS
0.1% · 2th percentile
CWE
—

Report tools

JSON

Action score

22

Monitor

Low priority for now.

CVSS
22 / 40 · 5.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

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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

Affected versions

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

  • linux linux kernel2.6.33.1 and later · before 6.1.168
  • linux linux kernel6.2 and later · before 6.6.131
  • linux linux kernel6.7 and later · before 6.12.80
  • linux linux kernel6.13 and later · before 6.18.21
  • linux linux kernel6.19 and later · before 6.19.11
  • linux linux kernel2.6.33
  • linux linux kernel7.0

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

    • 2.6.33affected
    • 30fff9231fad757c061285e347b33c5149c2c2e4 and later · before d6ace0dbcbb7fd285738bb87b42b71b01858c952affected · git
    • 30fff9231fad757c061285e347b33c5149c2c2e4 and later · before 2297e38114316b26ae02f2d205c49b5511c5ed55affected · git
    • 30fff9231fad757c061285e347b33c5149c2c2e4 and later · before f1bed05a832ae79be5f7a105da56810eaa59a5f1affected · git
    • 30fff9231fad757c061285e347b33c5149c2c2e4 and later · before 18d84c45def3671d5c89fbdd5d4ab8a3217fe4b4affected · git
    • 30fff9231fad757c061285e347b33c5149c2c2e4 and later · before 0a360f7f73a06ac88f18917055fbcc79694252d7affected · git
    • 30fff9231fad757c061285e347b33c5149c2c2e4 and later · before e537dd15d0d4ad989d56a1021290f0c674dd8b28affected · git
    • before 2.6.33not affected · semver
    • 6.1.168 and later · up to and including 6.1.*not affected · semver
    • 6.6.131 and later · up to and including 6.6.*not affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.170-16.1.170-1
Debian:13linuxbefore 6.12.85-16.12.85-1
Debian:14linuxbefore 6.19.11-16.19.11-1
Red Hat:enterprise_linux:10.2kernelbefore 0:6.12.0-211.52.1.el10_20:6.12.0-211.52.1.el10_2
Red Hat:enterprise_linux:10.2kernel-64kbefore 0:6.12.0-211.52.1.el10_20:6.12.0-211.52.1.el10_2
Red Hat:enterprise_linux:10.2kernel-64k-corebefore 0:6.12.0-211.52.1.el10_20:6.12.0-211.52.1.el10_2
Red Hat:enterprise_linux:10.2kernel-64k-debugbefore 0:6.12.0-211.52.1.el10_20:6.12.0-211.52.1.el10_2
Red Hat:enterprise_linux:10.2kernel-64k-debug-corebefore 0:6.12.0-211.52.1.el10_20:6.12.0-211.52.1.el10_2
Red Hat:enterprise_linux:10.2kernel-64k-debug-debuginfobefore 0:6.12.0-211.52.1.el10_20:6.12.0-211.52.1.el10_2
Red Hat:enterprise_linux:10.2kernel-64k-debug-develbefore 0:6.12.0-211.52.1.el10_20:6.12.0-211.52.1.el10_2
Red Hat:enterprise_linux:10.2kernel-64k-debug-devel-matchedbefore 0:6.12.0-211.52.1.el10_20:6.12.0-211.52.1.el10_2
Red Hat:enterprise_linux:10.2kernel-64k-debug-modulesbefore 0:6.12.0-211.52.1.el10_20:6.12.0-211.52.1.el10_2
Red Hat:enterprise_linux:10.2kernel-64k-debug-modules-corebefore 0:6.12.0-211.52.1.el10_20:6.12.0-211.52.1.el10_2
Red Hat:enterprise_linux:10.2kernel-64k-debug-modules-extrabefore 0:6.12.0-211.52.1.el10_20:6.12.0-211.52.1.el10_2
Red Hat:enterprise_linux:10.2kernel-64k-debuginfobefore 0:6.12.0-211.52.1.el10_20:6.12.0-211.52.1.el10_2
Red Hat:enterprise_linux:10.2kernel-64k-develbefore 0:6.12.0-211.52.1.el10_20:6.12.0-211.52.1.el10_2
Red Hat:enterprise_linux:10.2kernel-64k-devel-matchedbefore 0:6.12.0-211.52.1.el10_20:6.12.0-211.52.1.el10_2
Red Hat:enterprise_linux:10.2kernel-64k-modulesbefore 0:6.12.0-211.52.1.el10_20:6.12.0-211.52.1.el10_2
Red Hat:enterprise_linux:10.2kernel-64k-modules-corebefore 0:6.12.0-211.52.1.el10_20:6.12.0-211.52.1.el10_2
Red Hat:enterprise_linux:10.2kernel-64k-modules-extrabefore 0:6.12.0-211.52.1.el10_20:6.12.0-211.52.1.el10_2
Red Hat:enterprise_linux:10.2kernel-abi-stablelistsbefore 0:6.12.0-211.52.1.el10_20:6.12.0-211.52.1.el10_2
Red Hat:enterprise_linux:10.2kernel-corebefore 0:6.12.0-211.52.1.el10_20:6.12.0-211.52.1.el10_2
Red Hat:enterprise_linux:10.2kernel-debugbefore 0:6.12.0-211.52.1.el10_20:6.12.0-211.52.1.el10_2
Red Hat:enterprise_linux:10.2kernel-debug-corebefore 0:6.12.0-211.52.1.el10_20:6.12.0-211.52.1.el10_2

+89

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-2026-31501Apr 22, 2026 · net: ti: icssg-prueth: fix use-after-free of CPPI descriptor in RX path
    39Monitor
  • ← EarlierCVE-2026-31502Apr 22, 2026 · team: fix header_ops type confusion with non-Ethernet ports
    31Monitor
  • Later →CVE-2026-31504Apr 22, 2026 · net: fix fanout UAF in packet_release() via NETDEV_UP race
    31Monitor

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 Linux0a360f7f73a06ac88f18917055fbcc79694252d7Vendor (CNA)
Linux Linux18d84c45def3671d5c89fbdd5d4ab8a3217fe4b4Vendor (CNA)
Linux Linux2297e38114316b26ae02f2d205c49b5511c5ed55Vendor (CNA)
Linux Linuxd6ace0dbcbb7fd285738bb87b42b71b01858c952Vendor (CNA)
Linux Linuxe537dd15d0d4ad989d56a1021290f0c674dd8b28Vendor (CNA)
Linux Linuxf1bed05a832ae79be5f7a105da56810eaa59a5f1Vendor (CNA)
azl3 kernel 6.6.130.1-3 on Azure Linux 3.06.6.134.1-2 · CBL-Mariner ReleasesMicrosoft (MSRC)
cbl2 kernel 5.15.202.1-1 on CBL-Mariner 2.0Release NotesMicrosoft (MSRC)
debian:linux6.1.170-1 · Debian:12Package registry (OSV)
red hat:kernel-64k-debug-debuginfo0:6.12.0-211.52.1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:kernel-64k-debug-devel0:6.12.0-211.52.1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:kernel-64k-debug-devel-matched0:6.12.0-211.52.1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:kernel-64k-debuginfo0:6.12.0-211.52.1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:kernel-64k-devel0:6.12.0-211.52.1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:kernel-64k-devel-matched0:6.12.0-211.52.1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:kernel-debug-debuginfo0:6.12.0-211.52.1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:kernel-debug-devel0:6.12.0-211.52.1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:kernel-debug-devel-matched0:6.12.0-211.52.1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:kernel-debuginfo0:6.12.0-211.52.1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:kernel-debuginfo-common-aarch640:6.12.0-211.52.1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:kernel-debuginfo-common-ppc64le0:6.12.0-211.52.1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
rocky linux:kernel0:6.12.0-211.52.1.el10_2 · Rocky Linux:10Package registry (OSV)
suse:kernel-64kb6.4.0-150700.53.73.2 · SUSE:Linux Enterprise Module for Basesystem 15 SP7Package registry (OSV)
suse:kernel-default6.4.0-50.1 · SUSE:Linux Micro 6.0Package registry (OSV)
suse:kernel-default-base6.4.0-150700.53.73.2.150700.17.41.4 · SUSE:Linux Enterprise Module for Basesystem 15 SP7Package registry (OSV)
suse:kernel-docs6.4.0-150700.53.73.1 · SUSE:Linux Enterprise Module for Development Tools 15 SP7Package registry (OSV)
suse:kernel-kvmsmall6.4.0-50.1 · SUSE:Linux Micro 6.0Package registry (OSV)
suse:kernel-livepatch-SLE15-SP7-RT_Update_181-150700.1.5.1 · SUSE:Linux Enterprise Live Patching 15 SP7Package registry (OSV)
suse:kernel-obs-build6.4.0-150700.53.73.2 · SUSE:Linux Enterprise Module for Development Tools 15 SP7Package registry (OSV)
suse:kernel-rt6.4.0-50.1 · SUSE:Linux Micro 6.0Package registry (OSV)

+4

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.

No history yet (it accumulates with the daily EPSS job).

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.

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.

—

Bug bounty scope

No known public program.

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

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

—

CVSS vector

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

nvd-primary

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. Fix✗ → ✓

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

References

Show all references (8 more)

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

All records