Transferable End-to-End Optimization for Indirect Long-Term Memory Poisoning in LLM Agents

AuthorsChuanchao Zang, Jianing Wang, Wenyu Chen et al.

arXiv 20262026

TL;DR

PIPEPOISON uses chain-structured, weighted end-to-end optimization over write–retrieve–utilize pipelines to raise Attack Utilization Rate by 19.1 percentage points over the strongest baseline.

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THE PROBLEM

Stage-wise memory poisoning breaks under cross-stage interference (WSR drops 59.4% → 47.3%)

Existing indirect memory poisoning attacks optimize writing and retrieval separately, causing write success rate to fall from 59.4% to 47.3% after retrieval-oriented tuning.

This cross-stage interference and sequential transformation mean poisoned content that looks retrievable can be rewritten away, breaking long-term influence on agent planning and decisions.

HOW IT WORKS

PIPEPOISON: Transferable end-to-end optimization over write–retrieve–utilize

PIPEPOISON builds stage-level signals, chain-structured losses, and stability-calibrated configuration weights on local shadow systems to optimize a shared poisoning instance.

Think of PIPEPOISON as tuning one malicious "card" so it survives library cataloging, gets ranked highly during search, and then dominates the librarian’s final recommendation.

By explicitly modeling write, retrieve, and utilize as a chained objective, PIPEPOISON achieves persistent behavioral steering that a plain context window or stage-isolated optimization cannot provide.

DIAGRAM

End-to-end poisoning lifecycle in PIPEPOISON

This diagram shows how PIPEPOISON executes the write–retrieve–utilize pipeline on shadow configurations and feeds stage signals back into hint refinement.

DIAGRAM

Evaluation pipeline across agents, memories, and defenses

This diagram shows how PIPEPOISON is evaluated over 12 memory–agent configurations, transfer scenarios, and eight defenses using WSR, RSR@5, and AUR.

PROCESS

How PIPEPOISON Handles a Write–Retrieve–Utilize Lifecycle

  1. 01

    Stage-Level Signals

    PIPEPOISON runs the poisoning content through shadow configurations and computes writing score Wi(x), retrieval score Ri(x,q), and utilization score Ui(x,q) for each pipeline.

  2. 02

    Chain-Structured Losses

    PIPEPOISON converts stage scores into chain-structured losses ℓi,w ℓi,r ℓi,u, encoding that retrieval and utilization are optimized only after writing succeeds.

  3. 03

    Weighted Multi-Configuration Optimization

    PIPEPOISON computes configuration weights πi and stage weights αj from current losses, forming a joint lifecycle score J(t) that emphasizes difficult stages and configurations.

  4. 04

    Hint Refinement and Poison Generation

    PIPEPOISON updates one of the stage hints h(t)w h(t)r h(t)u using shadow feedback, regenerates poisoning content, and repeats until the lifecycle score exceeds threshold η.

KEY CONTRIBUTIONS

Key Contributions

  • 01

    End-to-end formulation of indirect memory poisoning

    PIPEPOISON formalizes indirect long-term memory poisoning as optimization over the full write–retrieve–utilize lifecycle, explaining why WSR drops 59.4% → 47.3% and RSR 93.1% → 77.9% under stage-wise tuning.

  • 02

    Transferable PIPEPOISON framework

    PIPEPOISON introduces stage-level signals, chain-structured losses, and stability-calibrated configuration and stage weights to generate poisoning content that transfers across heterogeneous agent and memory configurations.

  • 03

    Comprehensive evaluation across systems and defenses

    PIPEPOISON is evaluated on three agent frameworks, four memory mechanisms, multiple LLM and embedding setups, and eight defenses, achieving 73.4% AUR and retaining 41%–66% AUR under defenses.

RESULTS

By the Numbers

Attack Utilization Rate

73.4%

+19.1 percentage points over MemMorph

Write Success Rate

76.1%

+13.1 percentage points over MemMorph

Retrieval Success Rate@5

94.2%

+8.4 percentage points over MINJA

AUR under defenses

41%–66%

PIPEPOISON remains effective across eight defenses including Llama Guard and A-MemGuard

On 300 tasks from LongMemEval, LoCoMo, and BEAM across 12 memory–agent configurations, PIPEPOISON reaches 73.4% Attack Utilization Rate, compared to 54.3% for MemMorph and 48.2% for MINJA. These results show that end-to-end, weighted lifecycle optimization lets PIPEPOISON maintain poisoned influence through writing, retrieval, and utilization.

BENCHMARK

By the Numbers

On 300 tasks from LongMemEval, LoCoMo, and BEAM across 12 memory–agent configurations, PIPEPOISON reaches 73.4% Attack Utilization Rate, compared to 54.3% for MemMorph and 48.2% for MINJA. These results show that end-to-end, weighted lifecycle optimization lets PIPEPOISON maintain poisoned influence through writing, retrieval, and utilization.

BENCHMARK

Average performance across 12 matched memory–agent configurations

Attack Utilization Rate (AUR) comparison across indirect and direct memory poisoning baselines.

KEY INSIGHT

The Counterintuitive Finding

Retrieval-oriented optimization in existing attacks reduces write success rate from 59.4% to 47.3%, and memory writing reduces retrieval success rate from 93.1% to 77.9%.

This is surprising because tuning content to be more retrievable intuitively should help attacks, yet PIPEPOISON shows that ignoring upstream transformations can erase those gains and harm end-to-end success.

WHY IT MATTERS

What this unlocks for the field

PIPEPOISON unlocks a way to treat long-term memory poisoning as a single chained objective, rather than three isolated stages, using shadow pipelines only.

Builders can now stress-test agent memory systems against realistic, transferable poisoning that survives writing, competes in retrieval, and actually changes behavior, revealing lifecycle-wide vulnerabilities that stage-local defenses miss.

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