VulnerabilityPublished 20 Jul 2026Updated 9 Oct 2026

CVE-2026-63952: Linux kernel · memfd: deny writeable mappings when implying SEAL_WRITE

Affects Linux kernelSource GCVE Database

Authoritative record:CVE-2026-63952· High 8.4

Not known to be exploited · CVSS 8.4 High · fixed in 6.8.0-1066.69~22.04.1 : patch Linux kernel soon.

Data as of 26 Oct 2026, 14:05 UTC

CVSS 3.1 base score

8.4High

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.
Patch: Available – fixed in 6.8.0-1066.69~22.04.1, 6.8.0-1070.78~22.04.1, 6.8.0-1068.75~22.04.1 +37

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

Attack Vector: Local
Attack Complexity: Low
Privileges Required: Low
User Interaction: None
Scope: Changed
Confidentiality: High
Integrity: High
Availability: None

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: Changed: An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.
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: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 19 Jul 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
Ubuntu 26.04 LTSlinux`pkg:deb/ubuntu/linux?arch=source&distro=resolute`Other threats	Affected <7.0.0-28.28	Fixed in 7.0.0-28.28
Ubuntu 26.04 LTSlinux-aws`pkg:deb/ubuntu/linux-aws?arch=source&distro=resolute`Other threats	Affected <7.0.0-1009.9	Fixed in 7.0.0-1009.9
Ubuntu 26.04 LTSlinux-azure`pkg:deb/ubuntu/linux-azure?arch=source&distro=resolute`Other threats	Affected <7.0.0-1010.10	Fixed in 7.0.0-1010.10
Ubuntu 26.04 LTSlinux-azure-fde`pkg:deb/ubuntu/linux-azure-fde?arch=source&distro=resolute`Other threats	Affected <7.0.0-1009.9	Fixed in 7.0.0-1009.9
Ubuntu 26.04 LTSlinux-gcp`pkg:deb/ubuntu/linux-gcp?arch=source&distro=resolute`Other threats	Affected <7.0.0-1008.8	Fixed in 7.0.0-1008.8
Ubuntu 26.04 LTSlinux-gke`pkg:deb/ubuntu/linux-gke?arch=source&distro=resolute`Other threats	Affected <7.0.0-1003.4	Fixed in 7.0.0-1003.4

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

AI-suggested

An official patch is available and should be applied to affected Linux kernel versions to resolve this vulnerability. The fix ensures that implied seals are applied before denying writable mappings, restoring the intended security guarantees of memfd seals. Users should update their systems to the patched kernel versions as provided by their distribution vendors. No additional mitigation steps are indicated by the vendor advisory.

Description

A vulnerability in the Linux kernel's memfd subsystem allowed bypassing the write sealing (SEAL_WRITE) when the execute seal (SEAL_EXEC) was applied. This flaw meant that a memfd could appear write-sealed but still be modified, breaking the intended security contract. The issue was fixed by adjusting the order of applying seals to ensure writeable mappings are properly denied. The vulnerability affects multiple Linux kernel versions prior to 7.0.0-28.28 and several specific older versions. A patch is available, and no known exploits are reported in the wild.

Impact

An attacker with local privileges could exploit this vulnerability to bypass the write sealing on memfd objects, potentially modifying memory regions that should be write-protected. This could lead to privilege escalation or compromise of system integrity. The CVSS score of 8.4 indicates a high impact on confidentiality and integrity, with no impact on availability. No known exploits in the wild have been reported.

Summary

The Linux kernel memfd subsystem had a vulnerability where adding SEAL_EXEC implied SEAL_WRITE, but the implied seal was set after the check that denies writable mappings. This allowed an attacker to use SEAL_EXEC to apply SEAL_WRITE while still having writable mappings, violating the write seal contract. The fix involved adding the implied seals before the writable mapping denial check. This vulnerability affects various Linux kernel versions including multiple 4.15.x, 5.0.x, 5.3.x, and versions prior to 7.0.0-28.28. The issue is tracked as CVE-2026-63952 with a CVSS 3.1 score of 8.4 (high severity).

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 25 Oct 2026, 12:59 UTC

Technical details

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