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NVD / CVE Program· CNA Linux

CVE-2026-31429: net: skb: fix cross-cache free of KFENCE-allocated skb head

Noroxi assessment

Priority: Monitor (action score 22/100)

  • Public proof-of-concept code exists (GitHub); there is no record of exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.25% (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 0f42e3f4fe2a58394e37241d02d9ca6ab7b7d516, 128b03ccb2582a643983a48a37fda58df80edbde, 2d64618ea846d8d033477311f805ca487d6a6696.

Low priority for now. Upgrade to Linux Linux 0f42e3f4fe2a58394e37241d02d9ca6ab7b7d516, 128b03ccb2582a643983a48a37fda58df80edbde, 2d64618ea846d8d033477311f805ca487d6a6696 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: skb: fix cross-cache free of KFENCE-allocated skb head SKB_SMALL_HEAD_CACHE_SIZE is intentionally set to a non-power-of-2 value (e.g. 704 on x86_64) to avoid collisions with generic kmalloc bucket sizes. This ensures that skb_kfree_head() can reliably use skb_end_offset to distinguish skb heads allocated from skb_small_head_cache vs. generic kmalloc caches. However, when KFENCE is enabled, kfence_ksize() returns the exact requested allocation size instead of the slab bucket size. If a caller (e.g. bpf_test_init) allocates skb head data via kzalloc() and the requested size happens to equal SKB_SMALL_HEAD_CACHE_SIZE, then slab_build_skb() -> ksize() returns that exact value. After subtracting skb_shared_info overhead, skb_end_offset ends up matching SKB_SMALL_HEAD_HEADROOM, causing skb_kfree_head() to incorrectly free the object to skb_small_head_cache instead of back to the original kmalloc cache, resulting in a slab cross-cache free: kmem_cache_free(skbuff_small_head): Wrong slab cache. Expected skbuff_small_head but got kmalloc-1k Fix this by always calling kfree(head) in skb_kfree_head(). This keeps the free path generic and avoids allocator-specific misclassification for KFENCE objects.

MediumCVSS 5.5 · v3.1—Proof of concept Fix available
Published
Apr 20, 2026
Updated
Jun 17, 2026
EPSS
0.2% · 17th percentile

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 · 0.2%

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  • 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

Affected versions

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

  • linux linux kernel6.3 and later · before 6.6.136
  • linux linux kernel6.7 and later · before 6.12.82
  • linux linux kernel6.13 and later · before 6.18.23
  • linux linux kernel6.19 and later · before 6.19.13
  • 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

    • 6.3affected
    • bf9f1baa279f0758dc2297080360c5a616843927 and later · before 128b03ccb2582a643983a48a37fda58df80edbdeaffected · git
    • bf9f1baa279f0758dc2297080360c5a616843927 and later · before 60313768a8edc7094435975587c00c2d7b834083affected · git
    • bf9f1baa279f0758dc2297080360c5a616843927 and later · before 2d64618ea846d8d033477311f805ca487d6a6696affected · git
    • bf9f1baa279f0758dc2297080360c5a616843927 and later · before 474e00b935db250cac320d10c1d3cf4e44b46721affected · git
    • bf9f1baa279f0758dc2297080360c5a616843927 and later · before 0f42e3f4fe2a58394e37241d02d9ca6ab7b7d516affected · git
    • before 6.3not affected · semver
    • 6.6.136 and later · up to and including 6.6.*not affected · semver
    • 6.12.82 and later · up to and including 6.12.*not affected · semver
    • 6.18.23 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
Debian:13linuxbefore 6.12.85-16.12.85-1
Debian:14linuxbefore 6.19.13-16.19.13-1
openSUSE:Leap 16.0dtb-aarch64before 6.12.0-160000.36.16.12.0-160000.36.1
openSUSE:Leap 16.0kernel-64kbbefore 6.12.0-160000.36.16.12.0-160000.36.1
openSUSE:Leap 16.0kernel-azurebefore 6.12.0-160000.36.16.12.0-160000.36.1
openSUSE:Leap 16.0kernel-defaultbefore 6.12.0-160000.36.16.12.0-160000.36.1
openSUSE:Leap 16.0kernel-default-basebefore 6.12.0-160000.36.1.160000.2.176.12.0-160000.36.1.160000.2.17
openSUSE:Leap 16.0kernel-docsbefore 6.12.0-160000.36.16.12.0-160000.36.1
openSUSE:Leap 16.0kernel-kvmsmallbefore 6.12.0-160000.36.16.12.0-160000.36.1
openSUSE:Leap 16.0kernel-obs-buildbefore 6.12.0-160000.36.16.12.0-160000.36.1
openSUSE:Leap 16.0kernel-obs-qabefore 6.12.0-160000.36.16.12.0-160000.36.1
openSUSE:Leap 16.0kernel-rtbefore 6.12.0-160000.36.16.12.0-160000.36.1
openSUSE:Leap 16.0kernel-sourcebefore 6.12.0-160000.36.16.12.0-160000.36.1
openSUSE:Leap 16.0kernel-symsbefore 6.12.0-160000.36.16.12.0-160000.36.1
openSUSE:Leap 16.0kernel-zfcpdumpbefore 6.12.0-160000.36.16.12.0-160000.36.1
SUSE:Linux Enterprise Live Patching 15 SP7kernel-livepatch-SLE15-SP7_Update_17before 1-150700.15.3.11-150700.15.3.1
SUSE:Linux Enterprise Live Patching 15 SP7kernel-livepatch-SLE15-SP7-RT_Update_17before 1-150700.1.3.11-150700.1.3.1
SUSE:Linux Enterprise Module for Basesystem 15 SP7kernel-64kbbefore 6.4.0-150700.53.63.16.4.0-150700.53.63.1
SUSE:Linux Enterprise Module for Basesystem 15 SP7kernel-defaultbefore 6.4.0-150700.53.63.16.4.0-150700.53.63.1
SUSE:Linux Enterprise Module for Basesystem 15 SP7kernel-default-basebefore 6.4.0-150700.53.63.1.150700.17.37.16.4.0-150700.53.63.1.150700.17.37.1
SUSE:Linux Enterprise Module for Basesystem 15 SP7kernel-sourcebefore 6.4.0-150700.53.63.16.4.0-150700.53.63.1
SUSE:Linux Enterprise Module for Basesystem 15 SP7kernel-zfcpdumpbefore 6.4.0-150700.53.63.16.4.0-150700.53.63.1
SUSE:Linux Enterprise Module for Development Tools 15 SP7kernel-docsbefore 6.4.0-150700.53.63.16.4.0-150700.53.63.1
SUSE:Linux Enterprise Module for Development Tools 15 SP7kernel-obs-buildbefore 6.4.0-150700.53.63.16.4.0-150700.53.63.1

+23

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-2026-31427Apr 13, 2026 · netfilter: nf_conntrack_sip: fix use of uninitialized rtp_addr in process_sdp
    22Monitor
  • ← EarlierCVE-2026-31428Apr 13, 2026 · netfilter: nfnetlink_log: fix uninitialized padding leak in NFULA_PAYLOAD
    22Monitor
  • Later →CVE-2026-31430Apr 20, 2026 · X.509: Fix out-of-bounds access when parsing extensions
    28Monitor

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 Linux0f42e3f4fe2a58394e37241d02d9ca6ab7b7d516Vendor (CNA)
Linux Linux128b03ccb2582a643983a48a37fda58df80edbdeVendor (CNA)
Linux Linux2d64618ea846d8d033477311f805ca487d6a6696Vendor (CNA)
Linux Linux474e00b935db250cac320d10c1d3cf4e44b46721Vendor (CNA)
Linux Linux60313768a8edc7094435975587c00c2d7b834083Vendor (CNA)
debian:linux6.12.85-1 · Debian:13Package registry (OSV)
opensuse:dtb-aarch646.12.0-160000.36.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-64kb6.12.0-160000.36.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-azure6.12.0-160000.36.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-default6.12.0-160000.36.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-default-base6.12.0-160000.36.1.160000.2.17 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-docs6.12.0-160000.36.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-kvmsmall6.12.0-160000.36.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-obs-build6.12.0-160000.36.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-obs-qa6.12.0-160000.36.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-rt6.12.0-160000.36.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-source6.12.0-160000.36.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-syms6.12.0-160000.36.1 · openSUSE:Leap 16.0Package registry (OSV)
suse:kernel-64kb6.12.0-160000.36.1 · SUSE:Linux Micro 6.2Package registry (OSV)
suse:kernel-azure6.12.0-160000.36.1 · SUSE:Linux Enterprise Server 16.0Package registry (OSV)
suse:kernel-default6.4.0-48.1 · SUSE:Linux Micro 6.0Package registry (OSV)
suse:kernel-default-base6.4.0-48.1.21.25 · SUSE:Linux Micro 6.0Package registry (OSV)
suse:kernel-docs6.12.0-160000.36.1 · SUSE:Linux Enterprise Server 16.0Package registry (OSV)
suse:kernel-kvmsmall6.4.0-48.1 · SUSE:Linux Micro 6.0Package registry (OSV)
suse:kernel-obs-build6.12.0-160000.36.1 · SUSE:Linux Micro Extras 6.2Package registry (OSV)
suse:kernel-obs-qa6.12.0-160000.36.1 · SUSE:Linux Enterprise Server 16.0Package registry (OSV)
suse:kernel-rt6.4.0-48.1 · SUSE:Linux Micro 6.0Package registry (OSV)
suse:kernel-source6.4.0-48.1 · SUSE:Linux Micro 6.0Package registry (OSV)
suse:kernel-source-rt6.4.0-48.1 · SUSE:Linux Micro 6.0Package registry (OSV)
suse:kernel-syms6.12.0-160000.36.1 · SUSE:Linux Micro Extras 6.2Package registry (OSV)

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 ×1

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 GitHubstars:12026-04-24

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. Published
  2. First PoC+4 d
  3. TodayNov 4, 2026+198 d

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)

CWE-401 · Missing Release of Memory after Effective Lifetime

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 (4 more)

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

All records