VulnerabilityPublished 23 Apr 2026Updated 19 Oct 2026

CVE-2026-31533: Linux kernel · Use After Free

Affects Linux kernelSource CVE Database V5

Not known to be exploited · CVSS 9.8 Critical · fixed in aa9facde6c5005205874c37db3fd25799d741baf : patch Linux kernel as a priority.

Data as of 26 Oct 2026, 17:30 UTC

CVSS 3.1 base score

9.8Critical

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

EPSS

0.3% chance of exploitation in 30 days – higher than 33% 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: Total control over the software or total information disclosure

CISA SSVC assessment, 2026-10-16.

Patch

Available – fixed in aa9facde6c5005205874c37db3fd25799d741baf, a9b8b18364fffce4c451e6f6fd218fa4ab646705, 2694d408b0e595024e0fc1d64ff9db0358580f74 +8

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: High
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: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to 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 23 Apr 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 >=5.15.160 <5.15.203 >=6.1.84 <6.1.169 >=6.6.18 <6.6.135 >=6.7.6 <6.8	Fixed in aa9facde6c5005205874c37db3fd25799d741baf a9b8b18364fffce4c451e6f6fd218fa4ab646705 2694d408b0e595024e0fc1d64ff9db0358580f74 414fc5e5a5aff776c150f1b86770e0a25a35df3a 6.8 6.6.135 6.1.169 5d70eb25b41e9b010828cd12818b06a0c3b04412 5.15.203 02f3ecadb23558bbe068e6504118f1b712d4ece0 0e43e0a3c94044acc74b8e0927c27972eb5a59e8
LinuxLinux	Affected =6.8	Fixed in–

AI-suggested

A fix for this vulnerability has been released in Linux kernel versions 5.15.203, 6.1.169, 6.6.135, 6.8, and corresponding commit hashes. Users and administrators should upgrade to these fixed versions or later to remediate the issue. No additional mitigation steps are required beyond applying the official patch.

Description

CVE-2026-31533 is a critical use-after-free vulnerability in the Linux kernel's TLS encryption code. It occurs due to a double cleanup of internal structures when handling the -EBUSY error path in tls_do_encryption(), leading to memory corruption and potential use-after-free conditions. This flaw can cause kernel memory corruption and potentially allow attackers to execute arbitrary code or cause denial of service. The issue affects multiple Linux kernel versions prior to the fixed releases. A patch has been released to correct the error handling and prevent double cleanup.

Impact

The vulnerability allows kernel memory corruption through a use-after-free condition in the TLS encryption path. This can lead to arbitrary code execution in kernel context or denial of service by crashing the kernel. The CVSS score of 9.8 reflects the critical severity and the potential for complete system compromise without requiring privileges or user interaction.

Summary

This vulnerability in the Linux kernel's net/tls subsystem arises from improper handling of the -EBUSY error path in the tls_do_encryption() function. Specifically, when crypto_aead_encrypt() returns -EBUSY, the encryption request is enqueued for asynchronous processing. The asynchronous callback tls_encrypt_done() performs cleanup by restoring the scatterlist entry and decrementing encrypt_pending. However, if tls_encrypt_async_wait() returns an error synchronously, tls_do_encryption() performs the same cleanup again, causing a double decrement of encrypt_pending and double restoration of the scatterlist. This corrupts the encrypt_pending sentinel, causing tls_encrypt_async_wait() to skip waiting for pending callbacks. Consequently, a subsequent sendmsg can free the tls_rec structure while a cryptd callback is still pending, leading to a use-after-free when the callback executes on freed memory. The fix involves skipping the synchronous cleanup when the async wait returns an error, ensuring cleanup is only done once.

CWE-416Use After Free (opens in a new tab)
Variant weaknessLikelihood of exploit: HighCWE Top 25 (2025): #7
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.
Architecture and Design · Language Selection
Choose a language that provides automatic memory management.
Implementation · Attack Surface Reduction
When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.
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)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 26 Oct 2026, 13:58 UTC

WeaknessesCWE-416

Technical details

References

Community reviews

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