CVE-2026-55273

CVE-2026-55273 is an improper input validation flaw (CWE-20) in the AppendCommentLine function of AnnotationProcessor.cpp in the Android platform, which Google's Android security team characterizes as a possible supply chain risk. It is exploited locally: an attacker who already has low-level code execution on a device needs no additional privileges and no user interaction to trigger the flaw. Successful exploitation yields local escalation of privilege, with high impact on confidentiality, integrity, and availability, consistent with the CVSS 3.1 score of 7.8 (AV:L/AC:L/PR:L/UI:N). Android devices and OEM builds that include the affected component are in scope; the flaw is addressed in the September 2026 Android Security Update. There are currently no reports of exploitation in the wild, no public proof-of-concept, and the flaw is not in CISA's Known Exploited Vulnerabilities catalog, with EPSS estimating only a 0.1% chance of exploitation in the next 30 days.

What to do: Apply the September 2026 Android security update as soon as it becomes available for your devices (check Settings > System > System update for the new patch level). OEMs, carriers, and AOSP maintainers should merge the upstream fix into their build trees, and since the flaw is flagged as a supply chain risk, rebuild or re-validate artifacts produced with the affected AnnotationProcessor component using patched tooling. No workaround is documented; given no known exploitation and very low EPSS, this can be handled in the normal patch cycle rather than as an emergency.