VulnerabilityPublished 8 May 2026Updated 19 Oct 2026

CVE-2026-43406: Linux kernel · libceph: prevent potential out-of-bounds reads in process_message_header()

Affects Linux kernelSource CVE Database V5

Not known to be exploited · CVSS 9.1 Critical · fixed in dbd857a9e1e33ea71eaf3e211877027e533770d1 : patch Linux kernel as a priority.

Data as of 26 Oct 2026, 14:01 UTC

CVSS 3.1 base score

9.1Critical

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

EPSS

0.6% chance of exploitation in 30 days – higher than 49% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

Exploitation: No evidence of active exploitation and no public proof of concept
Automatable: Attackers can reliably automate steps 1–4 of the kill chain
Technical impact: Limited control over the software or limited information exposure

CISA SSVC assessment, 2026-10-16.

Patch

Available – fixed in dbd857a9e1e33ea71eaf3e211877027e533770d1, 50156622eb0888e62541d715a98584480a1bc7cb, 75582aaa580c11aed4c7731cad6b068b700e7efb +4

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

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

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

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
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: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 8 May 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: 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 26 Oct 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.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, 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 to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ cd1a677cad994021b19665ed476aea63f5d54f31, < dbd857a9e1e33ea71eaf3e211877027e533770d1	Fixed in dbd857a9e1e33ea71eaf3e211877027e533770d1
LinuxLinux	Affected ≥ cd1a677cad994021b19665ed476aea63f5d54f31, < 50156622eb0888e62541d715a98584480a1bc7cb	Fixed in 50156622eb0888e62541d715a98584480a1bc7cb
LinuxLinux	Affected ≥ cd1a677cad994021b19665ed476aea63f5d54f31, < 75582aaa580c11aed4c7731cad6b068b700e7efb	Fixed in 75582aaa580c11aed4c7731cad6b068b700e7efb
LinuxLinux	Affected ≥ cd1a677cad994021b19665ed476aea63f5d54f31, < 035867ae6f18df0aeedb2a57a5b74091bd4e3fe8	Fixed in 035867ae6f18df0aeedb2a57a5b74091bd4e3fe8
LinuxLinux	Affected ≥ cd1a677cad994021b19665ed476aea63f5d54f31, < 76ccf21a12c5f6d6790bc32c7da82446d877b2f4	Fixed in 76ccf21a12c5f6d6790bc32c7da82446d877b2f4
LinuxLinux	Affected ≥ cd1a677cad994021b19665ed476aea63f5d54f31, < 69fe5af33fa3806f398d21c081d73c66e5523bc2	Fixed in 69fe5af33fa3806f398d21c081d73c66e5523bc2

AI-suggested

A fix is available and has been applied in the Linux kernel. Users and administrators should update affected Linux kernel versions to incorporate the patches identified by the fixed commit hashes. Since this is not a cloud service, manual patching is required. There are no indications of known exploits in the wild at this time.

Description

CVE-2026-43406 is a critical vulnerability in the Linux kernel's libceph component. It involves potential out-of-bounds reads in the process_message_header() function when message frames are corrupted or manipulated. This flaw can lead to memory safety issues by reading beyond intended buffer boundaries. The vulnerability has been fixed by adding explicit bounds checks before decoding message headers.

Impact

Successful exploitation of this vulnerability can lead to out-of-bounds memory reads, potentially exposing sensitive kernel memory contents and causing denial of service due to kernel crashes. The vulnerability does not impact integrity but has high confidentiality and availability impacts. It can be exploited remotely without privileges or user interaction.

Summary

This vulnerability affects the Linux kernel's libceph module, specifically in the process_message_header() function. If a message frame is maliciously corrupted such that the control segment length is less than the message header size, or if a non-message frame is crafted to appear as a message frame, out-of-bounds reads can occur. This is a memory safety issue classified under CWE-125 (Out-of-bounds Read). The fix involves performing explicit bounds checking before decoding the message header to prevent such reads. The vulnerability is rated critical with a CVSS 3.1 score of 9.1, reflecting network attack vector, low attack complexity, no privileges required, no user interaction, unchanged scope, high confidentiality impact, no integrity impact, and high availability impact.

CWE-125Out-of-bounds Read (opens in a new tab)
Base weaknessCWE Top 25 (2025): #8
The product reads data past the end, or before the beginning, of the intended buffer.
Implementation · Input Validation
Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
Architecture and Design · Language Selection
Use a language that provides appropriate memory abstractions.
OWASP Cheat Sheets
XML Security (opens in a new tab)
Mass Assignment (opens in a new tab)
OWASP ASVS 4.0.3
V13.3.1 (opens in a new tab)
V5.1.4 (opens in a new tab)
V5.1.3 (opens in a new tab)
Attack patterns
Overread Buffers (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 26 Oct 2026, 14:01 UTC

WeaknessesCWE-125

Technical details

References

Community reviews

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