VulnerabilityPublished 3 Nov 2026

CVE-2026-85033: zephyrproject zephyr · Dos

Affects zephyrproject zephyrSource CVE Database V5

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Not known to be exploited · CVSS 4.6 Medium : upgrade to 4.5.0 when convenient.

Data as of 3 Nov 2026, 13:58 UTC

CVSS 3.1 base score

4.6Medium

How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none

CVSS scores by source
CNA (zephyr)	CVSS 3.1	4.6

Patch: Available – fixed in 4.5.0

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

Attack Vector: Adjacent
Attack Complexity: Low
Privileges Required: Low
User Interaction: None
Scope: Unchanged
Confidentiality: Low
Integrity: None
Availability: Low

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Adjacent: The vulnerable component is bound to the network stack, but the attack is limited at the protocol level to a logically adjacent topology. This can mean an attack must be launched from the same shared physical (e.g., Bluetooth or IEEE 802.11) or logical (e.g., local IP subnet) network, or from within a secure or otherwise limited administrative domain (e.g., MPLS, secure VPN to an administrative network zone).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 3 Nov 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 3 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade zephyrproject zephyr to 4.5.0.

Affected software

Product	Affected	Fixed in
zephyrprojectzephyr	Affected >=4.4.0 <4.5.0	Fixed in 4.5.0
GitHubzephyr`pkg:github/zephyr`Other threats	Affected >=4.4.0 <4.5.0	Fixed in 4.5.0

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A fix is available in Zephyr version 4.5.0 that properly cancels the transmit work and releases all queued response buffers during disconnection, preventing stale transmit states. Users should upgrade affected Zephyr versions (>=4.4.0 <4.5.0) to 4.5.0 or later to remediate this vulnerability. No additional mitigation is required as the vulnerability requires a paired and in-range attacker and no user interaction.

Description

CVE-2026-85033 is a medium-severity denial of service vulnerability in the Zephyr project's AVRCP Target role implementation. It occurs when a remote paired AVRCP Controller sends a vendor-dependent command with a fragmented response and then drops the ACL link prematurely. This leaves stale buffers queued and the transmit state stuck, causing persistent loss of AVRCP Target functionality until reboot. The flaw also leaks one response buffer per cycle but does not cause memory corruption or use-after-free.

Impact

An attacker who is a paired AVRCP Controller within radio range can cause a persistent denial of service of the AVRCP Target role by triggering a fragmented vendor-dependent response and dropping the link prematurely. This prevents further vendor-dependent responses from being sent on subsequent connections using the same connection index, effectively disabling AVRCP Target functionality until the device is rebooted. Additionally, each exploit cycle leaks one response buffer from a limited pool, potentially impacting resource availability. There is no memory corruption or use-after-free risk.

Summary

The vulnerability in Zephyr's AVRCP Target role arises from improper cleanup during link teardown. The avrcp_disconnected() handler fails to cancel ongoing transmit work and release queued response buffers when the ACL link drops mid-fragmented response. Because the transmit context is stored in the buffer's user_data, stale buffers with TX_ONGOING flags remain queued. Subsequent connections reusing the same connection index encounter the stale buffer, causing all further vendor-dependent responses to be blocked indefinitely. This results in a denial of service of AVRCP Target functionality and leaks response buffers from a shallow pool. The issue requires a paired peer within radio range and no user interaction. The fix, implemented in Zephyr 4.5.0, cancels the transmit work and unreferences all queued buffers on disconnect, resetting the transmit state machine.

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Affected software

Description

AI analysisMachine-generated, updated 3 Nov 2026, 13:45 UTC

Technical details

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