a2a-rs CVE-2026-113706

Requires an authenticated, network-reachable request to an a2a-rs server (versions ≤0.4.3) that exposes the task-listing/history path handled by InMemoryTaskStore, with the attacker supplying a client-controlled historyLength / page_size argument. Exploitation is LIMITED by: the need for valid low-privilege credentials to the A2A server (PR:L), deployment actually using the in-memory task store, and the server exposing the vulnerable list/history endpoint. Impact is bounded to disclosure of task-history records the pagination was meant to limit - no write, no code execution, no service disruption.

This is a medium-severity information-disclosure flaw (CVSS 4.0 base 5.1) and should be treated as a moderate-priority patch rather than an emergency. The supplied CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:L/UI:P/VC:L/VI:N/VA:N) is internally consistent with the code evidence: the attacker reaches the server over the network (AV:N), needs low-level authenticated access to the A2A server (PR:L), and achieves only limited confidentiality impact (VC:L) with no integrity or availability effect. The patch (commit 68f1b7e / PR #122) caps the page size at MAX_PAGE_SIZE=100 and adds strict page-token/status validation, confirming the root cause is unbounded/over-large responses driven by client-controlled paging parameters (historyLength / page_size) that leak more task history than intended. No EPSS score, CISA KEV listing, or public POC was provided in the input, so exploitation probability signals are absent - this is a disclosed-and-patched issue, not a known exploited one. One signal to flag: VulDB rates UI:P (passive user interaction required) while the flaw is a direct parameter manipulation by the requester, which would normally be UI:N; this mild inconsistency slightly lowers the vendor score and should be verified, but does not change the overall medium rating. Net: real but low-urgency, driven by severity-of-impact rather than any evidence of real-world exploitation.

An authenticated client of an a2a-rs-based agent server sends a task-listing or history request with an oversized historyLength / page_size value. Because the in-memory task store did not cap the page size before the fix, the server returns more task-history records than the pagination contract intended, disclosing task data to the requester. No public exploit code was identified in the provided data; exploitation requires valid (low-privilege) access to the server.