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NVD / CVE Program· CNA zephyr

CVE-2026-5590: net: ip/tcp: Null pointer dereference can be triggered by a race condition

Noroxi assessment

Priority: Monitor (action score 21/100)

  • 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: 0.19% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. A low-privileged account is enough. No user action is required. Special conditions such as timing or configuration are required.
  • Fixed version: zephyrproject-rtos Zephyr 4.3.1.

Low priority for now. Upgrade to zephyrproject-rtos Zephyr 4.3.1 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

A race condition during TCP connection teardown can cause tcp_recv() to operate on a connection that has already been released. If tcp_conn_search() returns NULL while processing a SYN packet, a NULL pointer derived from stale context data is passed to tcp_backlog_is_full() and dereferenced without validation, leading to a crash.

MediumCVSS 5.3 · v3.1—No exploit Fix available
Published
Apr 5, 2026
Updated
Oct 15, 2026
EPSS
0.1% · 9th percentile

Report tools

JSON

Action score

21

Monitor

Low priority for now.

CVSS
21 / 40 · 5.3 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
5.3
CNA · zephyr
6.4
1.1 point gap

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

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.

Follow CVE-2026-5590

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
zephyrprojectzephyr

Affected versions

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

  • zephyrproject zephyrup to 4.3.0 inclusive

Versions reported by the vendor

Affected version ranges reported by the assigning authority (zephyr). Independent of NVD's CPE analysis and usually ahead of it.

  • zephyrproject-rtos Zephyr

    • before 4.3.1affected · git

Same product

zephyrproject: all records

Other highest-scoring records for the same primary product.

  • CVE-2023-4260Potential off-by-one buffer overflow vulnerability in the Zephyr FS subsystem
    40Plan
  • CVE-2021-3625Buffer overflow in Zephyr USB DFU DNLOAD
    40Plan
  • CVE-2020-10071Insufficient publish message length validation in MQTT
    40Plan

Published before and after this one in the same product

  • ← EarlierCVE-2026-4179Mar 16, 2026 · stm32: usb: Infinite while loop in Interrupt Handler
    24Monitor
  • ← EarlierCVE-2026-1679Mar 28, 2026 · net: eswifi socket send payload length not bounded
    31Monitor
  • Later →CVE-2026-1677May 11, 2026 · net: TLS 1.2 connections allowed on TLS 1.3 sockets
    21Monitor

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
zephyrproject-rtos Zephyr4.3.1Vendor (CNA)

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-2026-10678107 days apartNULL-pointer / out-of-bounds write in Zephyr MCTP I2C+GPIO target binding driven by an unauthenticated I2C controller
    32Monitor
  • CVE-2026-11810127 days apartNULL-pointer dereference in UpdateHub OTA agent on empty inner metadata array (remote DoS)
    30Monitor
  • CVE-2026-15891161 days apartNULL pointer dereference in Zephyr MQTT-SN client when removing a non-responsive gateway
    30Monitor
  • CVE-2026-79976199 days apartNULL pointer dereference in the MCTP I2C+GPIO target binding triggerable by a peer I2C controller
    28Monitor
  • CVE-2026-1059384 days apartRemotely triggerable NULL-pointer dereference in Bluetooth LE Audio BAP unicast client QoS-state handling
    26Monitor
  • CVE-2026-82389204 days apartBluetooth Classic HFP AG wipes an object still linked in the SDP request list on connect failure, causing a NULL dereference
    26Monitor

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.
  • A low-privileged account is enough.
  • No user action is required.
  • Special conditions such as timing or configuration are required.

If successful

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

Weakness class (CWE)

CWE-476 · NULL Pointer Dereference

CVSS vector

CVSS:3.1/AV:N/AC:H/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✗ → ✓

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