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NVD / CVE Program· CNA Linux

CVE-2026-43233: netfilter: nf_conntrack_h323: fix OOB read in decode_choice()

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: 0.46% (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 2a3aac4205e7d2f1aca2e3827de8cdd517d36c4a, 35f1943d242e1b9f0b6e91c0c93bfb293a9f8224, 53d32735d77ab56cc3fc7bd53a7d099418f19be1.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 2a3aac4205e7d2f1aca2e3827de8cdd517d36c4a, 35f1943d242e1b9f0b6e91c0c93bfb293a9f8224, 53d32735d77ab56cc3fc7bd53a7d099418f19be1 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_choice() In decode_choice(), the boundary check before get_len() uses the variable `len`, which is still 0 from its initialization at the top of the function: unsigned int type, ext, len = 0; ... if (ext || (son->attr & OPEN)) { BYTE_ALIGN(bs); if (nf_h323_error_boundary(bs, len, 0)) /* len is 0 here */ return H323_ERROR_BOUND; len = get_len(bs); /* OOB read */ When the bitstream is exactly consumed (bs->cur == bs->end), the check nf_h323_error_boundary(bs, 0, 0) evaluates to (bs->cur + 0 > bs->end), which is false. The subsequent get_len() call then dereferences *bs->cur++, reading 1 byte past the end of the buffer. If that byte has bit 7 set, get_len() reads a second byte as well. This can be triggered remotely by sending a crafted Q.931 SETUP message with a User-User Information Element containing exactly 2 bytes of PER-encoded data ({0x08, 0x00}) to port 1720 through a firewall with the nf_conntrack_h323 helper active. The decoder fully consumes the PER buffer before reaching this code path, resulting in a 1-2 byte heap-buffer-overflow read confirmed by AddressSanitizer. Fix this by checking for 2 bytes (the maximum that get_len() may read) instead of the uninitialized `len`. This matches the pattern used at every other get_len() call site in the same file, where the caller checks for 2 bytes of available data before calling get_len().

HighCVSS 8.2 · v3.1—No exploit Fix available
Published
May 6, 2026
Updated
Oct 19, 2026
EPSS
0.4% · 40th 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 · 0.4%

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.

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  • 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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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 kernel4.15.1 and later · before 5.10.252
  • linux linux kernel5.11 and later · before 5.15.202
  • linux linux kernel5.16 and later · before 6.1.165
  • linux linux kernel6.2 and later · before 6.6.128
  • linux linux kernel6.7 and later · before 6.12.75
  • linux linux kernel6.13 and later · before 6.18.16
  • linux linux kernel6.19 and later · before 6.19.6
  • linux linux kernel4.15
  • 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

    • 4.15affected
    • ec8a8f3c31ddef0a7d9626c4b8a4baa30f3b80aa and later · before bcb50aa0b8f2b74a9fe5a1c7bee6f2657a288041affected · git
    • ec8a8f3c31ddef0a7d9626c4b8a4baa30f3b80aa and later · before 2a3aac4205e7d2f1aca2e3827de8cdd517d36c4aaffected · git
    • ec8a8f3c31ddef0a7d9626c4b8a4baa30f3b80aa and later · before 81f2fc5b0d0cf4696146f00f837596d10b92deadaffected · git
    • ec8a8f3c31ddef0a7d9626c4b8a4baa30f3b80aa and later · before 7ef82863d42261817a6394c6c881bd6757a70f16affected · git
    • ec8a8f3c31ddef0a7d9626c4b8a4baa30f3b80aa and later · before 53d32735d77ab56cc3fc7bd53a7d099418f19be1affected · git
    • ec8a8f3c31ddef0a7d9626c4b8a4baa30f3b80aa and later · before f0a83d0a4b7c127d32ac06d607a9214937716129affected · git
    • ec8a8f3c31ddef0a7d9626c4b8a4baa30f3b80aa and later · before 35f1943d242e1b9f0b6e91c0c93bfb293a9f8224affected · git
    • ec8a8f3c31ddef0a7d9626c4b8a4baa30f3b80aa and later · before baed0d9ba91d4f390da12d5039128ee897253d60affected · git
    • before 4.15not affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
AlmaLinux:8bpftoolbefore 4.18.0-553.164.1.el8_104.18.0-553.164.1.el8_10
AlmaLinux:8kernelbefore 4.18.0-553.164.1.el8_104.18.0-553.164.1.el8_10
AlmaLinux:8kernel-abi-stablelistsbefore 4.18.0-553.164.1.el8_104.18.0-553.164.1.el8_10
AlmaLinux:8kernel-corebefore 4.18.0-553.164.1.el8_104.18.0-553.164.1.el8_10
AlmaLinux:8kernel-cross-headersbefore 4.18.0-553.164.1.el8_104.18.0-553.164.1.el8_10
AlmaLinux:8kernel-debugbefore 4.18.0-553.164.1.el8_104.18.0-553.164.1.el8_10
AlmaLinux:8kernel-debug-corebefore 4.18.0-553.164.1.el8_104.18.0-553.164.1.el8_10
AlmaLinux:8kernel-debug-develbefore 4.18.0-553.164.1.el8_104.18.0-553.164.1.el8_10
AlmaLinux:8kernel-debug-modulesbefore 4.18.0-553.164.1.el8_104.18.0-553.164.1.el8_10
AlmaLinux:8kernel-debug-modules-extrabefore 4.18.0-553.164.1.el8_104.18.0-553.164.1.el8_10
AlmaLinux:8kernel-develbefore 4.18.0-553.164.1.el8_104.18.0-553.164.1.el8_10
AlmaLinux:8kernel-docbefore 4.18.0-553.164.1.el8_104.18.0-553.164.1.el8_10
AlmaLinux:8kernel-headersbefore 4.18.0-553.164.1.el8_104.18.0-553.164.1.el8_10
AlmaLinux:8kernel-modulesbefore 4.18.0-553.164.1.el8_104.18.0-553.164.1.el8_10
AlmaLinux:8kernel-modules-extrabefore 4.18.0-553.164.1.el8_104.18.0-553.164.1.el8_10
AlmaLinux:8kernel-rtbefore 4.18.0-553.164.1.rt7.505.el8_104.18.0-553.164.1.rt7.505.el8_10
AlmaLinux:8kernel-rt-corebefore 4.18.0-553.164.1.rt7.505.el8_104.18.0-553.164.1.rt7.505.el8_10
AlmaLinux:8kernel-rt-debugbefore 4.18.0-553.164.1.rt7.505.el8_104.18.0-553.164.1.rt7.505.el8_10
AlmaLinux:8kernel-rt-debug-corebefore 4.18.0-553.164.1.rt7.505.el8_104.18.0-553.164.1.rt7.505.el8_10
AlmaLinux:8kernel-rt-debug-develbefore 4.18.0-553.164.1.rt7.505.el8_104.18.0-553.164.1.rt7.505.el8_10
AlmaLinux:8kernel-rt-debug-modulesbefore 4.18.0-553.164.1.rt7.505.el8_104.18.0-553.164.1.rt7.505.el8_10
AlmaLinux:8kernel-rt-debug-modules-extrabefore 4.18.0-553.164.1.rt7.505.el8_104.18.0-553.164.1.rt7.505.el8_10
AlmaLinux:8kernel-rt-develbefore 4.18.0-553.164.1.rt7.505.el8_104.18.0-553.164.1.rt7.505.el8_10
AlmaLinux:8kernel-rt-modulesbefore 4.18.0-553.164.1.rt7.505.el8_104.18.0-553.164.1.rt7.505.el8_10

+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-2026-43223May 6, 2026 · media: pvrusb2: fix URB leak in pvr2_send_request_ex
    22Monitor
  • ← EarlierCVE-2026-43228May 6, 2026 · hfs: Replace BUG_ON with error handling for CNID count checks
    22Monitor
  • Later →CVE-2026-43234May 6, 2026 · team: avoid NETDEV_CHANGEMTU event when unregistering slave
    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 Linux2a3aac4205e7d2f1aca2e3827de8cdd517d36c4aVendor (CNA)
Linux Linux35f1943d242e1b9f0b6e91c0c93bfb293a9f8224Vendor (CNA)
Linux Linux53d32735d77ab56cc3fc7bd53a7d099418f19be1Vendor (CNA)
Linux Linux7ef82863d42261817a6394c6c881bd6757a70f16Vendor (CNA)
Linux Linux81f2fc5b0d0cf4696146f00f837596d10b92deadVendor (CNA)
Linux Linuxbaed0d9ba91d4f390da12d5039128ee897253d60Vendor (CNA)
Linux Linuxbcb50aa0b8f2b74a9fe5a1c7bee6f2657a288041Vendor (CNA)
Linux Linuxf0a83d0a4b7c127d32ac06d607a9214937716129Vendor (CNA)
almalinux:kernel5.14.0-687.41.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k5.14.0-687.41.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-core5.14.0-687.41.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug5.14.0-687.41.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-core5.14.0-687.41.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-devel5.14.0-687.41.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-devel-matched5.14.0-687.41.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-modules5.14.0-687.41.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-modules-core5.14.0-687.41.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-modules-extra5.14.0-687.41.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-devel5.14.0-687.41.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-devel-matched5.14.0-687.41.1.el9_8 · AlmaLinux:9Package registry (OSV)
debian:linux6.1.170-1 · Debian:12Package registry (OSV)
red hat:kernel-64k-debug-debuginfo0:5.14.0-687.41.1.el9_8 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-64k-debug-devel0:5.14.0-687.41.1.el9_8 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-64k-debug-devel-matched0:5.14.0-687.41.1.el9_8 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-64k-debuginfo0:5.14.0-687.41.1.el9_8 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-64k-devel0:5.14.0-687.41.1.el9_8 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-64k-devel-matched0:5.14.0-687.41.1.el9_8 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-debug-debuginfo0:5.14.0-687.41.1.el9_8 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-debug-devel0:5.14.0-687.41.1.el9_8 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-debug-devel-matched0:5.14.0-687.41.1.el9_8 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)

+5

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).

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
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 (7 more)

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

All records