VulnerabilityPublished 25 Jul 2026

CVE-2026-64324: Linux kernel · udf: validate free block extents against the partition length

Source GCVE Database

Authoritative record:CVE-2026-64324· High 7.8

Not known to be exploited · CVSS 7.8 High · fixed in fdd6229d2ae9914c1f25d1041db0f4f312a4fa76 : patch Linux kernel soon.

Data as of 26 Oct 2026, 14:05 UTC

CVSS 3.1 base score

7.8High

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

EPSS: 0.1% chance of exploitation in 30 days – higher than 5% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in fdd6229d2ae9914c1f25d1041db0f4f312a4fa76, fb49099206c5c57af28a157249fa7bcb5518f99e, be87de7789a82a030a4896bc7683415ec9fa6f2b +12

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

Attack Vector: Local
Attack Complexity: Low
Privileges Required: Low
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: 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: 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 25 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.

ghsa-mpf7-xmx2-frhw

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected >=5.10.224 <5.10.261 >=5.15.165 <5.15.212 >=6.1.105 <6.1.178 >=6.6.46 <6.6.145 >=4.19.320 <4.20 >=5.4.282 <5.5 >=6.10.5 <6.11	Fixed in fdd6229d2ae9914c1f25d1041db0f4f312a4fa76 fb49099206c5c57af28a157249fa7bcb5518f99e be87de7789a82a030a4896bc7683415ec9fa6f2b b54aee5652fcd7c23a0904a4623ec462c3edc70c 335202ab25b01fdd45889ff25eab70864686dea3 9442d75429b0c556292a7454fe888d54259f5240 12af328d2ee8d68e81ba612246d0b54b22d23e1f 6.11 6.6.145 6.1.178 5f0419457f89dce1a3f1c8e62a3adf2f39ab8168 5.15.212 5.10.261 5.5 4.20
LinuxLinux	Affected =6.11	Fixed in–

AI-suggested

A fix has been implemented in the Linux kernel to properly validate free block extents against the partition length and prevent out-of-range bitmap indexing. Users should apply the official kernel updates that include this fix. Systems that require root or CAP_SYS_ADMIN to mount UDF filesystems are less exposed. No additional mitigation is required beyond applying the vendor's patch when available.

Description

In the Linux kernel, the following vulnerability has been resolved: udf: validate free block extents against the partition length udf_free_blocks() checks the logical block number and count against the partition length, but drops the extent offset from that final bound. A crafted extent can pass the guard while logicalBlockNum + offset + count points past the partition, which later indexes past the space bitmap array. A single ftruncate(2) on a file backed by such an extent reliably panics the kernel. This is a local availability issue. On desktop systems where UDisks/polkit allows the active user to mount removable UDF media without CAP_SYS_ADMIN, an unprivileged local user can supply the crafted filesystem and trigger the panic by truncating a writable file on it. Systems that require root or CAP_SYS_ADMIN to mount the image have a higher prerequisite. No confidentiality or integrity impact is claimed: the reproduced primitive is an out-of-bounds read of a bitmap pointer slot followed by a kernel panic. Use the already computed logicalBlockNum + offset + count value for the partition length check. Also make load_block_bitmap() reject an out-of-range block group before indexing s_block_bitmap[], so corrupted callers cannot walk past the flexible array.

Impact

This vulnerability leads to a local denial of service by causing a kernel panic when a specially crafted UDF filesystem extent is accessed and truncated. There is no known impact on confidentiality or integrity. The attack requires local access and the ability to mount or have mounted a crafted UDF filesystem. Systems that restrict mounting to privileged users have a higher barrier to exploitation.

Summary

The Linux kernel's udf_free_blocks() function previously validated logical block numbers and counts against the partition length but omitted the extent offset from this check. This allowed a crafted extent where logicalBlockNum + offset + count exceeded the partition length, leading to an out-of-bounds access of the space bitmap array. Triggering this condition via a file truncation (ftruncate(2)) on a file backed by such an extent causes a kernel panic, resulting in a local denial of service. On systems where unprivileged users can mount UDF media (e.g., desktop systems using UDisks/polkit), this vulnerability can be exploited without elevated privileges. The fix involves using the full sum (logicalBlockNum + offset + count) for boundary validation and adding checks in load_block_bitmap() to reject out-of-range block groups before accessing the bitmap array.

References

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