Side channel Vulnerabilities

Automatic Prefix Caching (APC) in multi-tenant LLM serving systems introduces a timing side-channel vulnerability that permits cross-tenant data leakage. APC shares computed Key-Value (KV) tensors across different users when their requests share identical initial tokens. Because reusing cached tensors is significantly faster than recomputing them, a measurable difference in Time-To-First-Token (TTFT) exists between cache hits and misses. An attacker can exploit this shared cache by sending…

A vulnerability in multi-tenant LLM serving frameworks allows attackers to reconstruct the private prompts of other users via an active Key-Value (KV) cache side-channel. Frameworks that utilize shared KV caches alongside specific scheduling policies, such as Longest Prefix Match (LPM), prioritize waiting requests based on the length of their matched prefix tokens. An attacker can exploit this by iteratively sending batches of guessed tokens mixed with dummy queries. If a guessed token matches…

LLM serving frameworks utilizing continuous batching and PagedAttention (such as vLLM, SGLang, and Orca) are vulnerable to a resource exhaustion Denial-of-Service attack known as "Fill and Squeeze." An unprivileged remote attacker can exploit the deterministic state transitions of the scheduler's memory management to induce severe latency or service denial. The attack leverages a side-channel vulnerability where Inter-Token Latency (ITL) correlates linearly with global KV-cache usage due to…

A side-channel information leakage vulnerability exists in the "locate-then-edit" paradigm of Large Language Model (LLM) knowledge editing, specifically affecting algorithms such as ROME, MEMIT, and AlphaEdit. The parameter update matrix ($\Delta W$) generated during the editing process preserves the algebraic structure of the edited data. Specifically, the row space of the parameter difference matrix encodes a mathematical fingerprint of the key vectors associated with the edited subjects. An…

Semantic caching mechanisms in LLM applications are vulnerable to cross-tenant cache key collision attacks (CacheAttack) due to the inherent mathematical conflict between locality-preserving fuzzy hashing and cryptographic collision resistance (the avalanche effect). An attacker can leverage gradient-based search algorithms to optimize an adversarial discrete suffix that, when appended to a malicious prompt, forces its output embedding vector to collide with the embedding of a targeted benign…

Large Language Model (LLM) inference APIs that expose top-k logits or log-probabilities are vulnerable to model extraction and cloning. An attacker can execute a two-stage attack to replicate the proprietary model without access to weights, gradients, or training data. First, by submitting fewer than 10,000 random queries and aggregating the returned unrounded logits, the attacker recovers the model's output projection matrix using Singular Value Decomposition (SVD). Second, the attacker…

Large Language Models (LLMs) exposed via public APIs are vulnerable to model fingerprinting attacks where an attacker can identify the exact backend model family and version (e.g., distinguishing Mistral-7B-v0.1 from v0.3) by analyzing response patterns. While traditional fingerprinting relies on manual query curation, this vulnerability is exacerbated by Reinforcement Learning (RL) based query optimization. An attacker can train an RL agent (specifically using Proximal Policy Optimization) to…

Multi-tenant Large Language Model (LLM) inference systems utilizing global Key-Value (KV) cache sharing are vulnerable to a timing side-channel attack. By measuring the Time-To-First-Token (TTFT) latency of crafted API requests, an unprivileged remote attacker can determine if specific token sequences have been previously processed and cached by the system for other users. This observable timing difference between cache hits (low TTFT) and cache misses (high TTFT) allows for the token-by-token…

A Time-of-Check to Time-of-Use (TOCTOU) vulnerability exists in LLM-enabled agentic systems that execute multi-step plans involving sequential tool calls. The vulnerability arises because plans are not executed atomically. An agent may perform a "check" operation (e.g., reading a file, checking a permission) in one tool call, and a subsequent "use" operation (e.g., writing to the file, performing a privileged action) in another tool call. A temporal gap between these calls, often used for LLM…

Large Language Models (LLMs) are vulnerable to activation steering attacks that bypass safety and privacy mechanisms. By manipulating internal attention head activations using lightweight linear probes trained on refusal/disclosure behavior, an attacker can induce the model to reveal Personally Identifiable Information (PII) memorized during training, including sensitive attributes like sexual orientation, relationships, and life events. The attack does not require adversarial prompts or…