CVE-2026-98959 : 詳細

CVE-2026-98959

9.8
/
緊急
2026-10-23
13h17 +00:00
Network
2026-10-24
14h16 +00:00
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CVE の説明

In the Linux kernel, the following vulnerability has been resolved: btrfs: fix xattr replace when multiple xattrs are packed in the same item If we have a btrfs_dir_item item that packs multiple xattrs and then we replace the value of one of them (with the setxattr(2) family of syscalls) with another value of a different size, we end up not having a fully initialized btrfs_dir_item, resulting in a corruption that the tree checker will detect at extent buffer writeback time. This is because in btrfs_setxattr() when we find a btrfs_dir_item with multiple xattrs (due to the crc32c hash of their name being the same) we delete one of the xattr items (btrfs_dir_item) and then insert a new one, but the deletion and insertion results in shifting existing data in the leaf and therefore when the new value of a xattr has a different size, the new btrfs_dir_item is placed in a leaf section that was not initialized and we only copy the value's data and set the value's length in the new btrfs_dir_item, without setting the name, the name's length, the key (which must be all zeroes for xattrs), flags (BTRFS_FT_XATTR) and transaction ID. The following script reproduces the issue: $ cat test.sh #!/bin/bash DEV=/dev/sdi MNT=/mnt/sdi mkfs.btrfs -f $DEV mount $DEV $MNT touch $MNT/testfile # Add two xattrs that, on btrfs, have the same hash (crc32c) for their # name and therefore are packed into the same btrfs_dir_item. setfattr -n user.foobar -v 123 $MNT/testfile setfattr -n user.WvG1c1Td -v qwerty $MNT/testfile # Verify the xattrs are present. echo "xattrs before:" getfattr --absolute-names --dump $MNT/testfile # Now replace the value of the foobar xattr with a significantly larger # value. setfattr -n user.foobar -v abcdefghijklmnopqrstuvwxyz $MNT/testfile # Check the xattrs have the expected values. echo "xattrs after:" getfattr --absolute-names --dump $MNT/testfile umount $MNT Running it: $ ./test.sh (...) xattrs before: # file: /mnt/sdi/testfile user.WvG1c1Td="qwerty" user.foobar="123" xattrs after: # file: /mnt/sdi/testfile user.WvG1c1Td="qwerty" So the "user.foobar" xattr is missing and there was a transaction abort when unmounting the fs with the following traces in dmesg: $ dmesg [869800.159271] BTRFS warning (device sdi): access to eb bytenr 30474240 len 16384 out of range start 16015 len 25964 [869800.159293] ------------[ cut here ]------------ [869800.159296] WARNING: fs/btrfs/extent_io.c:4408 at report_eb_range+0x44/0x60 [btrfs], CPU#8: getfattr/2605179 [869800.168961] Modules linked in: btrfs dm_thin_pool (...) [869800.190527] CPU: 8 UID: 0 PID: 2605179 Comm: getfattr Tainted: G W 7.3.0-rc3-btrfs-next-244+ #1 PREEMPT(full) [869800.193726] Tainted: [W]=WARN [869800.194502] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.2-0-gea1b7a073390-prebuilt.qemu.org 04/01/2014 [869800.197576] RIP: 0010:report_eb_range+0x44/0x60 [btrfs] [869800.198985] Code: 48 8b 7b 18 (...) [869800.203531] RSP: 0018:ffffce4541937d58 EFLAGS: 00010246 [869800.204609] RAX: 0000000000000000 RBX: ffff8dde054b8738 RCX: 0000000000000000 [869800.206137] RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffffffffc04c92a0 [869800.207645] RBP: 0000000000003e8f R08: 0000000000000000 R09: 3fffffffffefffff [869800.226175] R10: ffffce4541937a88 R11: 0000000000000003 R12: 000000000000656c [869800.227594] R13: ffff8dde14be800f R14: 000000000000656c R15: 0000000000000069 [869800.229097] FS: 00007f59023bb780(0000) GS:ffff8de5788ed000(0000) knlGS:0000000000000000 [869800.231137] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [869800.232321] CR2: 0000558dc45e6a78 CR3: 0000000765b16004 CR4: 0000000000370ef0 [869800.233783] Call Trace: [869800.234330] [869800.234791] read_extent_buffer+0x4d/0x100 [btrfs] [869800.235898] btrfs_listxattr+0x199/0x240 [btrfs] [869800.236912] vfs_listxattr+0x51/0 ---truncated---

CVE の情報

メトリクス

メトリクス スコア 深刻度 CVSS ベクター 出典
V3.1 9.8 CRITICAL CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Base: Exploitabilty Metrics

The Exploitability metrics reflect the characteristics of the thing that is vulnerable, which we refer to formally as the vulnerable component.

Attack Vector

This metric reflects the context by which vulnerability exploitation is possible.

Network

The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed below, 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

This metric describes the conditions beyond the attacker’s control that must exist in order to exploit the vulnerability.

Low

Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success when attacking the vulnerable component.

Privileges Required

This metric describes the level of privileges an attacker must possess before successfully exploiting the vulnerability.

None

The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.

User Interaction

This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable component.

None

The vulnerable system can be exploited without interaction from any user.

Base: Scope Metrics

The Scope metric captures whether a vulnerability in one vulnerable component impacts resources in components beyond its security scope.

Scope

Formally, a security authority is a mechanism (e.g., an application, an operating system, firmware, a sandbox environment) that defines and enforces access control in terms of how certain subjects/actors (e.g., human users, processes) can access certain restricted objects/resources (e.g., files, CPU, memory) in a controlled manner. All the subjects and objects under the jurisdiction of a single security authority are considered to be under one security scope. If a vulnerability in a vulnerable component can affect a component which is in a different security scope than the vulnerable component, a Scope change occurs. Intuitively, whenever the impact of a vulnerability breaches a security/trust boundary and impacts components outside the security scope in which vulnerable component resides, a Scope change occurs.

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.

Base: Impact Metrics

The Impact metrics capture the effects of a successfully exploited vulnerability on the component that suffers the worst outcome that is most directly and predictably associated with the attack. Analysts should constrain impacts to a reasonable, final outcome which they are confident an attacker is able to achieve.

Confidentiality Impact

This metric measures the impact to the confidentiality of the information resources managed by a software component due to a successfully exploited vulnerability.

High

There is a 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. For example, an attacker steals the administrator's password, or private encryption keys of a web server.

Integrity Impact

This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information.

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 Impact

This metric measures the impact to the availability of the impacted component resulting from a successfully exploited vulnerability.

High

There is a 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).

Temporal Metrics

The Temporal metrics measure the current state of exploit techniques or code availability, the existence of any patches or workarounds, or the confidence in the description of a vulnerability.

Environmental Metrics

These metrics enable the analyst to customize the CVSS score depending on the importance of the affected IT asset to a user’s organization, measured in terms of Confidentiality, Integrity, and Availability.

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参考資料