CVE-2026-74576
UnratedPublished 2026-08-15
CVSS
—
Unrated
EPSS
—
exploit probability
Active Exploit
No
not yet listed
What is CVE-2026-74576?
In the Linux kernel, the following vulnerability has been resolved: mm/slab: prevent unbounded recursion in free path with new kmalloc type Commit 280ea9c3154b ("mm/slab: avoid allocating slabobj_ext array from its own slab") avoided recursive allocation of obj_exts from kmalloc caches of the same size, by bumping the obj_exts array's allocation size whenever the array size equals the size of the object being allocated. However, as reported by Danielle Costantino and Shakeel Butt, even slabs from kmalloc caches of different sizes can form a cycle by allocating obj_exts arrays from each other [1]: What happened: a KMALLOC_NORMAL slab's obj_exts array (used by allocation profiling / memcg accounting) is itself kmalloc()'d from a KMALLOC_NORMAL cache, so the "slab holds another slab's obj_exts array" relation can form cycles. With sizeof(struct slabobj_ext) == 16 and the host's geometry: - kmalloc-512 has 64 objects/slab -> array is 64*16 == 1024 bytes, served from kmalloc-1k; - kmalloc-1k has 32 objects/slab -> array is 32*16 == 512 bytes, served from kmalloc-512. A kmalloc-512 slab and a kmalloc-1k slab therefore hold each other's obj_exts array. Discarding one frees the other's array, which empties and discards that slab, which frees the first's array, and so on: __free_slab() -> free_slab_obj_exts() -> kfree() -> discard_slab() -> __free_slab() recurses along the cycle until the stack is exhausted. With memory allocation profiling, this allows unbounded recursion in the free path and led to a stack overflow on a production host in the Meta fleet [1]: BUG: TASK stack guard page was hit Oops: stack guard page RIP: 0010:kfree+0x8/0x5d0 Call Trace: __free_slab+0x66/0xc0 kfree+0x3f0/0x5d0 ... ( ~125x __free_slab <-> kfree ) ... <kernel driver freeing a resource> do_syscall_64 It is proposed [1] to resolve this issue by always serving the obj_exts array allocation from kmalloc caches (or large kmalloc) of sizes larger than the object size. However, as pointed out by Vlastimil Babka [2], this can waste an excessive amount of memory as slabs from large kmalloc sizes (e.g. kmalloc-8k) generally need obj_exts arrays much smaller than the object size. Therefore, rather than bumping the size, let us take a different approach; disallow formation of cycles between kmalloc types when allocating obj_exts arrays. Currently, all obj_exts arrays are served from normal kmalloc caches. Cycles cannot be created if obj_exts arrays of normal kmalloc caches are served from a special kmalloc type that can never have obj_exts arrays. To achieve this, create a new kmalloc type called KMALLOC_NO_OBJ_EXT. KMALLOC_NO_OBJ_EXT caches are created with SLAB_NO_OBJ_EXT flag when either 1) memory allocation profiling is not permanently disabled, or 2) kmalloc types with a priority higher than KMALLOC_CGROUP are aliased with KMALLOC_NORMAL. Sheaf bootstrapping for KMALLOC_NO_OBJ_EXT caches now must be deferred because allocation of a barn can trigger obj_exts array allocation of normal kmalloc caches when the KMALLOC_NO_OBJ_EXT cache for that size is not ready yet. For simplicity, perform bootstrapping of sheaves for all kmalloc caches later. Introduce a new slab alloc flag, SLAB_ALLOC_NO_OBJ_EXT, to prevent allocation of obj_exts arrays, and let kmalloc_slab() override the type to KMALLOC_NO_OBJ_EXT when specified. Note that kmalloc_type() remains unchanged because kmalloc_flags() bypasses the kmalloc fastpath. Do not pass SLAB_ALLOC_NO_RECURSE to kmalloc_flags() in alloc_slab_obj_exts() and instead use SLAB_ALLOC_NO_OBJ_EXT only when the objects are allocated from normal kmalloc caches. While this prevents unbounded recursive allocation of obj_exts, it allows KMALLOC_NO_OBJ_EXT caches to have sheaves. Since sheaf allocations specify SLAB_ALLOC_NO_RECURSE that prevents allocation of both sheaves and obj_exts arrays, the recursion depth is bounded. obj_exts arrays for non- ---truncated---
CVSS Score Explained
No CVSS score available for this CVE yet.
EPSS Exploitation Probability
No EPSS score yet — model needs more data on this CVE.
References & Patches
- ›https://git.kernel.org/stable/c/3e71bfbdd3fd81ee9fefd867fdb2be62bade4140
- ›https://git.kernel.org/stable/c/d01e88d421a6d07f35235600a43fbd0e551cf292
- ›https://git.kernel.org/stable/c/d9e6a7623938968e3752b67e37eaff097e559a54
- ›https://git.kernel.org/stable/c/ebefca49e4c69df24ba9307bfe0806230301d5c6
Track vulnerabilities for your stack
Tell us what tech you run — Node.js, Python, Java, nginx, whatever — and get a weekly email when new CVEs affect it.
Recent CVEs
- CVE-2026-19917A flaw has been found in code-projects Online Food Order System 1.0. The impacted element is an unknown function of the file delete_food_items1.php. Executing a manipulation of the argument checkbox can lead to sql injection. The attack can be executed remotely. The exploit has been published and may be used.2.1
- CVE-2026-73052SiYuan before v3.7.4 stores attribute-view field names without HTML escaping and interpolates them directly into option elements via innerHTML in the sort menu. Attackers can inject markup by renaming a database field to execute arbitrary JavaScript when users open the sort menu, with Node integration enabled in the desktop client enabling code execution.9.4
- CVE-2026-73053SiYuan versions before v3.7.4 contain a cross-site scripting vulnerability in the unicode2Emoji function that fails to sanitize codepoint branch output. Attackers can craft document icons with hex-encoded markup that executes in the renderer with Node integration enabled, achieving arbitrary code execution on the host system.9.4
- CVE-2026-73054SiYuan versions before v3.7.4 contain an authentication bypass vulnerability in the WebSocket endpoint caused by differential parsing of query parameters between authentication exemption and session quarantine checks. Unauthenticated attackers can craft a malicious WebSocket URI with duplicated query parameters to bypass access auth code validation and receive the live kernel event stream including document identifiers, titles, and operation logs.8.7
- CVE-2026-73055Shescape before 2.1.15 (and 3.0.0 before 3.0.2) fails to properly escape tilde (~) characters in assignment contexts on Unix systems where the shell is explicitly configured to "sh" or true and /bin/sh points to BusyBox. Using the escape and escapeAll APIs with untrusted input in an assignment prefixed to a command, an attacker can inject a tilde payload to disclose the user's home directory location and, depending on usage, alter the location on which a command operates.9.3
- CVE-2026-74764Pandora contains a path traversal vulnerability in its TAR archive extraction functionality. When processing a submitted TAR archive, the extractor passed archive member names directly to Python's tarfile.TarFile.extract() without applying an extraction filter.
An attacker able to submit a specially crafted TAR archive containing malicious member paths, such as paths using ../ sequences or absolute paths, could cause extracted files to be written outside the intended extraction directory. This may allow the attacker to overwrite files accessible to the Pandora worker process and could potentially result in application compromise, arbitrary code execution, or denial of service depending on the files targeted and the privileges of the Pandora process.
The vulnerability is corrected by using Python's filter='data' extraction filter, which rejects or sanitizes dangerous TAR members, including paths that escape the destination directory and unsafe link targets.
The weakness corresponds to MITRE's general path traversal category, which includes archive extraction cases where attacker-controlled filenames cause files to be written outside the intended directory.10.0