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NVD / CVE Program· CNA Linux

CVE-2026-23456: netfilter: nf_conntrack_h323: fix OOB read in decode_int() CONS case

Noroxi assessment

Priority: Monitor (action score 32/100)

  • 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: 0.54% (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 1e3a3593162c96e8a8de48b1e14f60c3b57fca8a, 41b417ff73a24b2c68134992cc44c88db27f482d, 52235bf88159a1ef16434ab49e47e99c8a09ab20.

Low priority for now. Upgrade to Linux Linux 1e3a3593162c96e8a8de48b1e14f60c3b57fca8a, 41b417ff73a24b2c68134992cc44c88db27f482d, 52235bf88159a1ef16434ab49e47e99c8a09ab20 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: netfilter: nf_conntrack_h323: fix OOB read in decode_int() CONS case In decode_int(), the CONS case calls get_bits(bs, 2) to read a length value, then calls get_uint(bs, len) without checking that len bytes remain in the buffer. The existing boundary check only validates the 2 bits for get_bits(), not the subsequent 1-4 bytes that get_uint() reads. This allows a malformed H.323/RAS packet to cause a 1-4 byte slab-out-of-bounds read. Add a boundary check for len bytes after get_bits() and before get_uint().

HighCVSS 8.2 · v3.1—No exploit Fix available
Published
Apr 3, 2026
Updated
Oct 19, 2026
EPSS
0.5% · 45th percentile

Report tools

JSON

Action score

32

Monitor

Low priority for now.

CVSS
32 / 40 · 8.2 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.5%

CISA SSVC decision

Exploitation
none
Automatable
yes
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · Linux
8.2
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

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Follow CVE-2026-23456

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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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 kernel2.6.17 and later · before 5.10.253
  • linux linux kernel5.11 and later · before 5.15.203
  • linux linux kernel5.16 and later · before 6.1.167
  • linux linux kernel6.2 and later · before 6.6.130
  • linux linux kernel6.7 and later · before 6.12.78
  • linux linux kernel6.13 and later · before 6.18.20
  • linux linux kernel6.19 and later · before 6.19.10
  • 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

    • 2.6.17affected
    • 5e35941d990123f155b02d5663e51a24f816b6f3 and later · before a2cd54b9348e485d338b3c132338a4410c99afafaffected · git
    • 5e35941d990123f155b02d5663e51a24f816b6f3 and later · before c95dc674ebf01ecfb40388b6facfc89b81fed3b7affected · git
    • 5e35941d990123f155b02d5663e51a24f816b6f3 and later · before 41b417ff73a24b2c68134992cc44c88db27f482daffected · git
    • 5e35941d990123f155b02d5663e51a24f816b6f3 and later · before 52235bf88159a1ef16434ab49e47e99c8a09ab20affected · git
    • 5e35941d990123f155b02d5663e51a24f816b6f3 and later · before 774a434f8c9c8602a976b2536f65d0172a07f4d2affected · git
    • 5e35941d990123f155b02d5663e51a24f816b6f3 and later · before 6bce72daeccca9aa1746e92d6c3d4784e71f2ebbaffected · git
    • 5e35941d990123f155b02d5663e51a24f816b6f3 and later · before fb6c3596823ec5dd09c2123340330d7448f51a59affected · git
    • 5e35941d990123f155b02d5663e51a24f816b6f3 and later · before 1e3a3593162c96e8a8de48b1e14f60c3b57fca8aaffected · git
    • before 2.6.17not 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 6.19.10-16.19.10-1

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-2026-23454Apr 3, 2026 · net: mana: fix use-after-free in mana_hwc_destroy_channel() by reordering teardown
    28Monitor
  • ← EarlierCVE-2026-23455Apr 3, 2026 · netfilter: nf_conntrack_h323: check for zero length in DecodeQ931()
    36Monitor
  • Later →CVE-2026-23457Apr 3, 2026 · netfilter: nf_conntrack_sip: fix Content-Length u32 truncation in sip_help_tcp()
    34Monitor

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 Linux1e3a3593162c96e8a8de48b1e14f60c3b57fca8aVendor (CNA)
Linux Linux41b417ff73a24b2c68134992cc44c88db27f482dVendor (CNA)
Linux Linux52235bf88159a1ef16434ab49e47e99c8a09ab20Vendor (CNA)
Linux Linux6bce72daeccca9aa1746e92d6c3d4784e71f2ebbVendor (CNA)
Linux Linux774a434f8c9c8602a976b2536f65d0172a07f4d2Vendor (CNA)
Linux Linuxa2cd54b9348e485d338b3c132338a4410c99afafVendor (CNA)
Linux Linuxc95dc674ebf01ecfb40388b6facfc89b81fed3b7Vendor (CNA)
Linux Linuxfb6c3596823ec5dd09c2123340330d7448f51a59Vendor (CNA)
debian:linux6.1.170-1 · Debian:12Package 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.

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

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

Weakness class (CWE)

CWE-125 · Out-of-bounds Read

CVSS vector

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

nvd-secondary

Attack context

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

ATT&CK techniques

—

Change log

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

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

References

Show all references (10 more)

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

All records