containerd overlaybd EUVD-2026-94691

Exploitation requires that the host consume an UNTRUSTED overlaybd blob pulled from a registry (i.e. an attacker-controlled or compromised image) AND that the deployment is running MULTIPLE overlaybd-backed containers - this multi-container scenario is the condition explicitly stated in the description and is why Scope is Changed. The malicious blob must contain a crafted LSMT header/trailer whose index_size/index_bytes value triggers the integer overflow in do_load_index during index loading. Limiting factors that reduce real-world risk: overlaybd must actually be in use as the snapshotter/backend (not the default for most container hosts), the attacker must get the victim to load their blob, Attack Complexity is High, and the impact is confined to availability (no confidentiality or integrity loss). Organizations that only pull overlaybd images from trusted, signed sources are not realistically exposed.

This is a genuine but low-to-moderate priority issue, not a top-tier emergency. The CVSS 3.1 base score is 6.8 (Medium) with vector AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H - critically, impact is Availability-only (C:N/I:N) despite the 'out-of-bounds heap access' wording, meaning the realistic outcome is a crash/denial of service of the overlaybd backend rather than code execution or data disclosure. Attack Complexity is High (AC:H), reflecting that an attacker must craft a malicious LSMT index that triggers the index_bytes integer overflow AND the victim must be running the specific scenario of multiple overlaybd-backed containers consuming an untrusted blob. The Scope:Changed metric is justified: the vulnerable overlaybd service process is distinct from the containers it serves, so a crash can impact co-located containers beyond the one that loaded the malicious blob. No EPSS score, KEV listing, or public POC was provided in the input, and the only references are source files plus the fix (PR #438 and two commits) - so there is no evidence of active exploitation or weaponization. Net: a legitimate supply-chain DoS vector worth patching, but the combination of availability-only impact, high attack complexity, and absence of exploitation signals means it does not warrant emergency prioritization over higher-impact RCE-class issues.

An attacker publishes a malicious overlaybd image/blob to a container registry (or compromises one the victim pulls from). When a host running multiple overlaybd-backed containers loads the crafted LSMT index, the integer overflow on index_bytes in do_load_index triggers an out-of-bounds heap access, crashing the overlaybd backend and denying service to co-located containers (Scope:Changed). No public exploit code was identified at time of analysis; exploitation is High complexity and requires the victim to consume the untrusted blob.