CVE-2026-80675 in Linux
Summary
by MITRE • 08/28/2026
In the Linux kernel, the following vulnerability has been resolved:
libbpf: Reject non-exclusive metadata maps in the signed loader
The loader verifies map->sha against the metadata hash in its instructions. map->sha is calculated when BPF_OBJ_GET_INFO_BY_FD is called on the frozen map.
While the map is frozen, the /signed loader/ must also ensure the map is exclusive, as, without exclusivity (which a hostile host could just omit when loading the loader), another BPF program with map access can mutate the contents afterwards, so the check passes on stale data.
With the extra check as part of the signed loader, it now refuses to move on with map->sha validation if the host set it up wrongly.
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Analysis
by VulDB Data Team • 08/28/2026
The Linux kernel's eBPF subsystem has addressed a critical security flaw within its signed BPF program loader mechanism, specifically targeting the integrity verification process for metadata maps. This vulnerability stems from an insufficient check during the loading phase of restricted or signed BPF programs. The core issue lies in how the verifier handles map exclusivity when validating cryptographic hashes against frozen map data structures. In a properly secured environment, the eBPF infrastructure relies on strict isolation and immutability guarantees to ensure that code execution remains within trusted boundaries. However, prior to this fix, the signed loader failed to enforce exclusive access rights for metadata maps during the hash validation step. This oversight created a scenario where the integrity checks could be bypassed or rendered ineffective due to race conditions or state manipulation by other components in the kernel.
The technical root of the vulnerability involves the interaction between the BPF object file descriptor operations and the loader's verification logic. When a signed BPF program is loaded, it typically includes metadata maps that store critical information such as hashes for further validation. The system calculates map->sha using the BPF_OBJ_GET_INFO_BY_FD ioctl call on these frozen maps to ensure they have not been tampered with after compilation. However, without enforcing exclusivity, another BPF program or kernel component could potentially gain access to modify the contents of this metadata map even while it is technically marked as frozen for the purpose of hash calculation. A hostile host environment or a compromised user-space process that loads the loader might omit setting the exclusive flag on these maps. This omission allows subsequent mutations by other programs with map access rights, meaning the hash check passes against stale or manipulated data rather than the intended original state.
From an operational impact perspective, this flaw undermines the fundamental security model of eBPF sandboxing and integrity verification. If an attacker can manipulate the metadata map contents after they are frozen but before their hashes are fully validated by the signed loader, they could potentially load a malicious BPF program that appears to be cryptographically valid. This bypasses the intended protection mechanisms designed to prevent arbitrary code execution or privilege escalation via eBPF programs. The ability to mutate data post-freeze effectively nullifies the trust anchor provided by the signature verification process. Consequently, systems relying on this feature for security enforcement could execute untrusted or malicious BPF code, leading to potential kernel compromise, denial of service through resource exhaustion, or unauthorized access to sensitive system resources protected by eBPF filters and hooks.
This vulnerability is categorized under CWE-20 Improper Input Validation as it relates to the failure to properly validate the state and integrity of input data structures during processing. Furthermore, it aligns with ATT&CK technique T1499 Endpoint Denial of Service or potentially T1055 Process Injection if leveraged for code execution, depending on how the malicious BPF program is utilized after bypassing the check. The mitigation involves a strict enforcement in the libbpf library and kernel loader logic to reject any metadata maps that are not explicitly marked as exclusive during the loading phase of signed programs. By refusing to proceed with map->sha validation if the host has set up the map incorrectly or without exclusivity, the system ensures that no external entity can alter the verification data after it is supposed to be immutable. This change reinforces the principle of least privilege and strict state management within the eBPF subsystem, ensuring that integrity checks are performed on data that cannot be tampered with by other concurrent processes. Administrators should ensure their systems are updated with kernel versions containing this fix to maintain the integrity of signed BPF program deployments.