CVE-2023-54145 in Linux
Summary
by MITRE • 12/24/2025
In the Linux kernel, the following vulnerability has been resolved:
bpf: drop unnecessary user-triggerable WARN_ONCE in verifierl log
It's trivial for user to trigger "verifier log line truncated" warning, as verifier has a fixed-sized buffer of 1024 bytes (as of now), and there are at least two pieces of user-provided information that can be output through this buffer, and both can be arbitrarily sized by user: - BTF names; - BTF.ext source code lines strings.
Verifier log buffer should be properly sized for typical verifier state output. But it's sort-of expected that this buffer won't be long enough in some circumstances. So let's drop the check. In any case code will work correctly, at worst truncating a part of a single line output.
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Analysis
by VulDB Data Team • 01/03/2026
The vulnerability identified as CVE-2023-54145 resides within the Linux kernel's eBPF (extended Berkeley Packet Filter) subsystem, specifically addressing an unnecessary user-triggerable warning mechanism in the verifier component. This flaw manifests as a WARN_ONCE message that appears when the verifier log line gets truncated, occurring due to a fixed-size buffer limitation of 1024 bytes. The issue stems from the verifier's inability to properly handle the dynamic sizing requirements of user-provided data elements, particularly when processing BTF (BPF Type Format) names and BTF.ext source code line strings that can be arbitrarily sized by malicious actors.
The technical implementation of this vulnerability exploits the fundamental design limitation of the verifier's logging mechanism where user-controllable inputs can easily overwhelm the fixed 1024-byte buffer. BTF names and BTF.ext source code line strings represent two primary vectors through which attackers can manipulate the verifier output, creating conditions where the warning message becomes truncated. The kernel's verifier component, designed to validate eBPF programs before execution, maintains this fixed buffer size despite the potentially unlimited growth of user-provided data elements. This design choice creates a scenario where legitimate system operations can be disrupted by crafted inputs that trigger the warning mechanism, effectively allowing users to induce kernel warnings through controlled input manipulation.
The operational impact of this vulnerability extends beyond simple warning generation, as it represents a potential denial-of-service vector within the kernel's security framework. While the immediate consequence appears to be a warning message truncation rather than system compromise, the underlying issue demonstrates poor resource management and buffer handling practices that could potentially be leveraged in more sophisticated attack scenarios. The vulnerability aligns with CWE-129, which addresses improper validation of length of input buffers, and could be categorized under ATT&CK technique T1059.007 for execution through kernel modules or eBPF programs. The fact that this warning can be triggered trivially by users indicates a design flaw in the kernel's input validation and resource allocation mechanisms, particularly within the eBPF verifier subsystem.
The resolution implemented for CVE-2023-54145 involves removing the unnecessary user-triggerable warning check, acknowledging that the buffer size limitation is expected to occur in certain circumstances and that the code functions correctly even when truncation happens. This approach follows the principle of defensive programming by accepting that buffer truncation is a legitimate operational condition rather than an error state. The mitigation strategy recognizes that while the truncation may result in loss of information from a single line output, the overall system functionality remains intact. This solution aligns with security best practices by eliminating the potential for resource exhaustion through user-triggered warnings while maintaining the core functionality of the verifier. The fix essentially transforms a potentially exploitable condition into a controlled operational behavior, reducing the attack surface while preserving the integrity of the eBPF verification process.
The broader implications of this vulnerability highlight the challenges in managing user-controllable inputs within kernel space, particularly in security-critical components like the eBPF verifier. The issue demonstrates the importance of considering edge cases and potential abuse scenarios during kernel development, especially when dealing with systems that process potentially untrusted user data. The resolution approach of removing the warning check rather than implementing complex buffer management solutions reflects a pragmatic approach to kernel security where simplicity and reliability take precedence over overly cautious error detection mechanisms. This vulnerability serves as a reminder of the delicate balance between providing useful diagnostic information and maintaining system stability under adversarial conditions, particularly within the Linux kernel's security architecture where eBPF programs play an increasingly critical role in network filtering, monitoring, and system observability.