CVE-2025-38012 in Linux
Summary
by MITRE • 06/18/2025
In the Linux kernel, the following vulnerability has been resolved:
sched_ext: bpf_iter_scx_dsq_new() should always initialize iterator
BPF programs may call next() and destroy() on BPF iterators even after new() returns an error value (e.g. bpf_for_each() macro ignores error returns from new()). bpf_iter_scx_dsq_new() could leave the iterator in an uninitialized state after an error return causing bpf_iter_scx_dsq_next() to dereference garbage data. Make bpf_iter_scx_dsq_new() always clear $kit->dsq so that next() and destroy() become noops.
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Analysis
by VulDB Data Team • 02/02/2026
The vulnerability identified as CVE-2025-38012 resides within the Linux kernel's scheduler extension subsystem, specifically affecting the BPF (Berkeley Packet Filter) iterator implementation for the scheduler. This flaw manifests in the bpf_iter_scx_dsq_new() function which is responsible for initializing BPF iterators used in scheduler contexts. The issue stems from improper error handling and state management within the iterator creation process, creating a scenario where iterator state becomes inconsistent when error conditions occur during the new() operation. The vulnerability is particularly concerning because it affects the core scheduler functionality that manages process execution and resource allocation across the system.
The technical implementation flaw occurs when BPF programs invoke the bpf_for_each() macro or similar iteration constructs that may ignore error returns from the new() function call. When bpf_iter_scx_dsq_new() encounters an error condition, it fails to properly initialize the iterator structure, leaving the iterator in an uninitialized state. This condition creates a dangerous scenario where subsequent calls to bpf_iter_scx_dsq_next() or bpf_iter_scx_dsq_destroy() attempt to operate on a partially initialized or corrupted iterator structure. The iterator's dsq member field remains in an undefined state, causing the next() function to dereference garbage data and potentially leading to memory corruption or system instability. This type of vulnerability aligns with CWE-457: Use of Uninitialized Variable and represents a classic case of improper state management in kernel code.
The operational impact of this vulnerability extends beyond simple memory corruption, potentially enabling privilege escalation or system instability in environments where BPF programs are actively used for scheduler monitoring or modification. Attackers could exploit this weakness by crafting malicious BPF programs that trigger the error path in bpf_iter_scx_dsq_new(), causing the system to execute code with elevated privileges or crash critical scheduler components. The vulnerability affects systems running Linux kernels that implement the scheduler extension framework and utilize BPF iterators for process scheduling operations. Given that BPF programs are increasingly used for system monitoring, performance analysis, and security enforcement, this flaw could be leveraged to compromise system integrity and availability. The ATT&CK framework categorizes this vulnerability under T1059.007: Command and Scripting Interpreter: Python, as malicious BPF programs could be used to exploit this weakness, and T1543.003: Create or Modify System Process: Systemd, since the compromised scheduler could affect system service management.
Mitigation strategies for CVE-2025-38012 require immediate kernel updates from vendors that address the specific iterator initialization issue in the scheduler extension subsystem. System administrators should prioritize patching affected kernels, particularly those running BPF programs or scheduler monitoring tools that interact with the affected code paths. The fix implemented in the kernel ensures that bpf_iter_scx_dsq_new() always clears the kit->dsq field regardless of error conditions, effectively making subsequent next() and destroy() operations no-ops when the iterator is in an invalid state. Additional defensive measures include implementing strict BPF program validation and monitoring for suspicious iterator usage patterns, as well as limiting the privileges of BPF programs that operate in scheduler contexts. Organizations should also consider implementing runtime monitoring to detect anomalous behavior in scheduler components that could indicate exploitation attempts. The vulnerability highlights the importance of proper error handling and state management in kernel code, particularly in high-privilege subsystems where memory corruption can lead to complete system compromise.