CVE-2024-53171 Detail

CVE-2024-53171

Score / Severity

7.8

High

CVE Descriptions

ubifs: authentication: Fix use-after-free in ubifs_tnc_end_commit

In the Linux kernel, the following vulnerability has been resolved: ubifs: authentication: Fix use-after-free in ubifs_tnc_end_commit After an insertion in TNC, the tree might split and cause a node to change its `znode->parent`. A further deletion of other nodes in the tree (which also could free the nodes), the aforementioned node's `znode->cparent` could still point to a freed node. This `znode->cparent` may not be updated when getting nodes to commit in `ubifs_tnc_start_commit()`. This could then trigger a use-after-free when accessing the `znode->cparent` in `write_index()` in `ubifs_tnc_end_commit()`. This can be triggered by running rm -f /etc/test-file.bin dd if=/dev/urandom of=/etc/test-file.bin bs=1M count=60 conv=fsync in a loop, and with `CONFIG_UBIFS_FS_AUTHENTICATION`. KASAN then reports: BUG: KASAN: use-after-free in ubifs_tnc_end_commit+0xa5c/0x1950 Write of size 32 at addr ffffff800a3af86c by task ubifs_bgt0_20/153 Call trace: dump_backtrace+0x0/0x340 show_stack+0x18/0x24 dump_stack_lvl+0x9c/0xbc print_address_description.constprop.0+0x74/0x2b0 kasan_report+0x1d8/0x1f0 kasan_check_range+0xf8/0x1a0 memcpy+0x84/0xf4 ubifs_tnc_end_commit+0xa5c/0x1950 do_commit+0x4e0/0x1340 ubifs_bg_thread+0x234/0x2e0 kthread+0x36c/0x410 ret_from_fork+0x10/0x20 Allocated by task 401: kasan_save_stack+0x38/0x70 __kasan_kmalloc+0x8c/0xd0 __kmalloc+0x34c/0x5bc tnc_insert+0x140/0x16a4 ubifs_tnc_add+0x370/0x52c ubifs_jnl_write_data+0x5d8/0x870 do_writepage+0x36c/0x510 ubifs_writepage+0x190/0x4dc __writepage+0x58/0x154 write_cache_pages+0x394/0x830 do_writepages+0x1f0/0x5b0 filemap_fdatawrite_wbc+0x170/0x25c file_write_and_wait_range+0x140/0x190 ubifs_fsync+0xe8/0x290 vfs_fsync_range+0xc0/0x1e4 do_fsync+0x40/0x90 __arm64_sys_fsync+0x34/0x50 invoke_syscall.constprop.0+0xa8/0x260 do_el0_svc+0xc8/0x1f0 el0_svc+0x34/0x70 el0t_64_sync_handler+0x108/0x114 el0t_64_sync+0x1a4/0x1a8 Freed by task 403: kasan_save_stack+0x38/0x70 kasan_set_track+0x28/0x40 kasan_set_free_info+0x28/0x4c __kasan_slab_free+0xd4/0x13c kfree+0xc4/0x3a0 tnc_delete+0x3f4/0xe40 ubifs_tnc_remove_range+0x368/0x73c ubifs_tnc_remove_ino+0x29c/0x2e0 ubifs_jnl_delete_inode+0x150/0x260 ubifs_evict_inode+0x1d4/0x2e4 evict+0x1c8/0x450 iput+0x2a0/0x3c4 do_unlinkat+0x2cc/0x490 __arm64_sys_unlinkat+0x90/0x100 invoke_syscall.constprop.0+0xa8/0x260 do_el0_svc+0xc8/0x1f0 el0_svc+0x34/0x70 el0t_64_sync_handler+0x108/0x114 el0t_64_sync+0x1a4/0x1a8 The offending `memcpy()` in `ubifs_copy_hash()` has a use-after-free when a node becomes root in TNC but still has a `cparent` to an already freed node. More specifically, consider the following TNC: zroot / / zp1 / / zn Inserting a new node `zn_new` with a key smaller then `zn` will trigger a split in `tnc_insert()` if `zp1` is full: zroot / \ / \ zp1 zp2 / \ / \ zn_new zn `zn->parent` has now been moved to `zp2`, *but* `zn->cparent` still points to `zp1`. Now, consider a removal of all the nodes _except_ `zn`. Just when `tnc_delete()` is about to delete `zroot` and `zp2`: zroot \ \ zp2 \ \ zn `zroot` and `zp2` get freed and the tree collapses: zn `zn` now becomes the new `zroot`. `get_znodes_to_commit()` will now only find `zn`, the new `zroot`, and `write_index()` will check its `znode->cparent` that wrongly points to the already freed `zp1`. `ubifs_copy_hash()` thus gets wrongly called with `znode->cparent->zbranch[znode->iip].hash` that triggers the use-after-free! Fix this by explicitly setting `znode->cparent` to `NULL` in `get_znodes_to_commit()` for the root node. The search for the dirty nodes ---truncated---

CVE Informations

Related Weaknesses

CWE-ID	Weakness Name	Source
CWE-416	Use After Free 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.

Metrics

Metrics	Score	Severity	CVSS Vector	Source
V3.1	7.8	HIGH	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H More informations 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. Local The vulnerable component is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. 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. Low The attacker 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 has the ability to access only non-sensitive resources. 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.	[email protected]

EPSS

EPSS is a scoring model that predicts the likelihood of a vulnerability being exploited.

EPSS Score

The EPSS model produces a probability score between 0 and 1 (0 and 100%). The higher the score, the greater the probability that a vulnerability will be exploited.

EPSS Percentile

The percentile is used to rank CVE according to their EPSS score. For example, a CVE in the 95th percentile according to its EPSS score is more likely to be exploited than 95% of other CVE. Thus, the percentile is used to compare the EPSS score of a CVE with that of other CVE.

EPSS First.org