CVE-2026-85747: 
cAdvisor 脆弱性分析と緩和策

CVE-2026-85747 is a security vulnerability in the registry client of the distribution/distribution project (the Docker Registry implementation) that allows unverified manifest and blob content to be accepted against requested digests. The flaw means that digest-pinned requests and pull-through caches are not properly validated, potentially allowing tampered or substituted content to be accepted. The CVE was inserted into Feedly's threat intelligence feed on September 24, 2026, and a fix was released in version v3.1.2 (GitHub Release). The CVE status is currently listed as "Reserved," and no CVSS score has been publicly assigned at this time.

The root cause of this vulnerability is insufficient content verification in the registry client: when fetching manifests or blobs by digest, the client does not verify that the returned content actually matches the requested digest (CWE-345: Insufficient Verification of Data Authenticity). This means a malicious or compromised registry — or a man-in-the-middle attacker — could serve arbitrary content in response to a digest-pinned pull request, and the client would accept it without detecting the mismatch. Pull-through cache configurations are particularly at risk, as they relay content from upstream registries and could propagate tampered layers or manifests. The fix, released in v3.1.2, enforces verification of manifest and blob content against the requested digest (GitHub Release).

Successful exploitation could allow an attacker to substitute arbitrary container image layers or manifests for legitimately requested content, undermining the integrity guarantees of digest-pinned image pulls. This could lead to the deployment of malicious container images in environments that rely on content-addressable digests for supply chain security, potentially enabling code execution within containerized workloads, data exfiltration, or lateral movement within a cluster. Environments using pull-through caches are especially exposed, as a compromised upstream or cache intermediary could silently serve tampered content to all downstream consumers (GitHub Release).

No public proof-of-concept exploit code, active in-the-wild exploitation, or threat actor attribution has been reported for CVE-2026-85747 at this time. The CVE remains in "Reserved" status, and no EPSS score or CISA KEV catalog entry has been identified. Exploitation would require either control of a registry or pull-through cache, or a man-in-the-middle position between the client and registry, limiting opportunistic exploitation but making it relevant in targeted supply chain attack scenarios (GitHub Release, Tenable Plugin).

Users should upgrade the distribution registry to version v3.1.2 or later, which enforces verification of manifest and blob content against the requested digest (GitHub Release). Organizations using pull-through cache configurations should prioritize patching, as these deployments are particularly exposed. Until an upgrade is possible, consider restricting access to the registry and pull-through cache endpoints and auditing image digests out-of-band using tools like cosign or notary to detect unexpected content substitution.

The vulnerability was noted in the LWCN developer newsletter for week 40 of 2026, indicating some community awareness (LWCN Newsletter). Tenable published a Nessus plugin (ID 349925) to detect affected installations (Tenable Plugin). No major vendor statements or significant social media discussion beyond these references have been identified at this time.