VulnerabilityPublished 1 May 2026Updated 19 Oct 2026

CVE-2026-31774: Linux kernel · io_uring/net: fix slab-out-of-bounds read in io_bundle_nbufs()

Affects Linux kernelSource CVE Database V5

Not known to be exploited · CVSS 7.1 High · fixed in c314b405dcc4d8b9041124f928f81715d6328bec : patch Linux kernel soon.

Data as of 26 Oct 2026, 15:59 UTC

CVSS 3.1 base score

7.1High

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

EPSS

0.1% chance of exploitation in 30 days – higher than 2% 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 cannot 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 c314b405dcc4d8b9041124f928f81715d6328bec, b948f9d5d3057b01188e36664e7c7604d1c8ecb5, 90ced24c500ad4e129e9e34b7e56fd7849e350b6 +1

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

Attack Vector: Local
Attack Complexity: Low
Privileges Required: Low
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: Local: The vulnerable component is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either: the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or remotely (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., tricking a legitimate user into opening a malicious document).
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: 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 1 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 Linux kernel to c314b405dcc4d8b9041124f928f81715d6328bec, b948f9d5d3057b01188e36664e7c7604d1c8ecb5, 90ced24c500ad4e129e9e34b7e56fd7849e350b6 or 1b655cd311344117d3052f6552cb20d9901c9d7c.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ a05d1f625c7aa681d8816bc0f10089289ad07aad, < c314b405dcc4d8b9041124f928f81715d6328bec	Fixed in c314b405dcc4d8b9041124f928f81715d6328bec
LinuxLinux	Affected ≥ a05d1f625c7aa681d8816bc0f10089289ad07aad, < b948f9d5d3057b01188e36664e7c7604d1c8ecb5	Fixed in b948f9d5d3057b01188e36664e7c7604d1c8ecb5
LinuxLinux	Affected ≥ a05d1f625c7aa681d8816bc0f10089289ad07aad, < 90ced24c500ad4e129e9e34b7e56fd7849e350b6	Fixed in 90ced24c500ad4e129e9e34b7e56fd7849e350b6
LinuxLinux	Affected ≥ a05d1f625c7aa681d8816bc0f10089289ad07aad, < 1b655cd311344117d3052f6552cb20d9901c9d7c	Fixed in 1b655cd311344117d3052f6552cb20d9901c9d7c
LinuxLinux	Affected =6.10	Fixed in–

AI-suggested

A fix is available and has been applied in the Linux kernel. The vulnerability is resolved by rejecting invalid length values early in the io_sendmsg_prep() and io_recvmsg_prep() functions. Users should update to the fixed Linux kernel versions containing the commits identified by hashes c314b405dcc4d8b9041124f928f81715d6328bec, b948f9d5d3057b01188e36664e7c7604d1c8ecb5, 90ced24c500ad4e129e9e34b7e56fd7849e350b6, and 1b655cd311344117d3052f6552cb20d9901c9d7c. No additional mitigations are indicated by the vendor advisory.

Description

CVE-2026-31774 is a high-severity vulnerability in the Linux kernel's io_uring/net subsystem involving a slab-out-of-bounds read in the io_bundle_nbufs() function. The issue arises because a 32-bit unsigned length (sqe->len) is stored in a signed int (sr->len), causing an integer overflow when values exceed INT_MAX. This overflow leads to a negative length that propagates through the code, ultimately causing an infinite loop and out-of-bounds read from kernel memory. The flaw is fixed by rejecting invalid length values early in the send and receive preparation functions.

Impact

This vulnerability allows a local attacker with the ability to submit io_uring requests to trigger a slab-out-of-bounds read in kernel memory. The CVSS score of 7.1 indicates high severity with potential for information disclosure (confidentiality impact is high) and denial of service (availability impact is high). Integrity is not impacted. There is no known exploitation in the wild at this time.

Summary

The vulnerability in Linux kernel io_uring/net occurs due to improper handling of the sqe->len field, which is a __u32 but stored into an int sr->len. When userspace passes a length exceeding INT_MAX (e.g., 0xFFFFFFFF), sr->len overflows to a negative value. This negative value propagates through the io_recv and io_send paths, causing an infinite loop in io_bundle_nbufs() that reads beyond the allocated iovec array, resulting in a slab-out-of-bounds read. The kernel's KASAN detected this out-of-bounds read during execution. The fix involves rejecting sr->len values that overflow early in io_sendmsg_prep() and io_recvmsg_prep(), preventing invalid lengths from causing the overflow and subsequent memory corruption.

CWE-190Integer Overflow or Wraparound (opens in a new tab)
Base weaknessLikelihood of exploit: Medium
The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.
Requirements
Ensure that all protocols are strictly defined, such that all out-of-bounds behavior can be identified simply, and require strict conformance to the protocol.
Requirements · Language Selection
Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Architecture and Design · Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
OWASP Cheat Sheets
XML Security (opens in a new tab)
Mass Assignment (opens in a new tab)
OWASP ASVS 4.0.3
V5.4.3 (opens in a new tab)
V13.3.1 (opens in a new tab)
V5.1.4 (opens in a new tab)
Attack patterns
Forced Integer Overflow (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

Loading reviews…

Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 26 Oct 2026, 15:47 UTC

WeaknessesCWE-190

Technical details

References

Community reviews

Related threats