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Response snapshot Oct 29, 2026, 01:26 UTC

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VulnerabilityCVE-2026-116575

Mem0: Cross-tenant conversation leak via unescaped delimiter collision in session-scope key (_build_session_scope)

Summary _build_session_scope() in mem0/memory/main.

Published Updated

At a glance

Exploited
Not known
Severity
6.3 Medium (CVSS 3.1)
Chance of exploitation
Not estimated
Sources
1 source

What to do

GitHub lists first patched versions: mem0ai: 2.0.18; mem0ai: 3.1.6. Confirm the affected range and upgrade guidance in the exact advisory.

Read GitHub-reviewed advisory GHSA-5324-3w58-qpp2 (opens a new tab)

What happened

Summary

_build_session_scope() in mem0/memory/main.py builds the conversation-history scope key used to fetch/store the last N raw messages by naively joining caller-supplied user_id/agent_id/run_id values with unescaped & and = delimiters:

def _build_session_scope(filters): parts = [] for key in sorted(["user_id", "agent_id", "run_id"]): val = filters.get(key) if val: parts.append(f"{key}={val}") return "&".join(parts)

_validate_and_trim_entity_id() (the only validation applied to these values) rejects only empty/whitespace-only strings — it never forbids & or =. This scope string is then used as an exact-match key against a SQLite column (storage.py: WHERE session_scope = ?) to fetch the last 10 raw messages for a given scope (main.py, Phase 0 of _add_to_vector_store, both sync and async).

Continue reading

Impact

Any caller who controls only their own run_id (or agent_id) — a very common integration shape, since apps frequently pass a client-/session-supplied identifier straight through as run_id without namespacing — can craft a value containing &user_id= (or &agent_id= ) that produces a scope string byte-for-byte identical to a different tenant's real scope string.

Concretely: Tenant A calls add(msgs, user_id="alice", run_id="proj-x") → scope "run_id=proj-x&user_id=alice". An attacker who can only set run_id calls add(msgs, run_id="proj-x&user_id=alice") → identical scope string. The attacker's next add() call:

1. Reads Tenant A's raw prior conversation via get_last_messages(session_scope) and splices it verbatim into the attacker's own LLM fact-extraction prompt — a direct cross-tenant confidentiality leak (conversation content, potentially including PII, credentials, etc.) 2. Writes into the same colliding row-set via save_messages(), whose eviction logic (DELETE FROM messages WHERE session_scope = ? AND id NOT IN (...))

can evict/interleave Tenant A's history — permanent cross-tenant data corruption, not just a read.

Reachable via the public Memory.add() / AsyncMemory.add() API, and by extension the REST server's POST /memories endpoint (which takes run_id/agent_id straight from the request body).

Reproduction

from mem0.memory.main import _build_session_scope

Tenant A: real user_id + run_id

scope_a = _build_session_scope({"user_id": "alice", "run_id": "proj-x"}) print(scope_a) # "run_id=proj-x&user_id=alice"

Attacker: controls only run_id, embeds a fake user_id inside it

scope_c = _build_session_scope({"run_id": "proj-x&user_id=alice"}) print(scope_c) # "run_id=proj-x&user_id=alice"

assert scope_a == scope_c # byte-for-byte collision

A full end-to-end proof (actual add() calls, no mocking of the vulnerable functions) confirms the attacker's subsequent add() call receives the victim's raw prior message content via get_last_messages.

Suggested Fix

Reject & and = in _validate_and_trim_entity_id(), alongside the existing whitespace check — this is the single validation chokepoint already used by every entry point (add, search, get_all, delete_all), so the fix is centralized. Alternatively/additionally, encode each component unambiguously (percent-encode each id, or use a length-prefixed/JSON-encoded scope key) so no valid-character combination in one field can ever collide with a different partition.

Also affected: TypeScript SDK (npm mem0ai)

The same flaw exists in mem0-ts/src/oss/src/memory/index.ts, Memory.buildSessionScope(), which joins agent_id/run_id/user_id into the same key=value&key=value string with the delimiters unescaped:

private buildSessionScope(filters: SearchFilters): string { const parts: string[] = []; for (const key of ["agent_id", "run_id", "user_id"].sort()) { const val = (filters as any)[key]; if (val) parts.push(${key}=${val}); } return parts.join("&"); }

The scope string is used the same way, as an exact-match key into the messages table via SQLiteManager.getLastMessages() and saveMessages(), so the identical forge, cross-tenant read and eviction all apply.

Verified against the current releases as of 2026-07-26: pip mem0ai v2.0.14 and npm mem0ai ts-v3.1.2 both still contain the unescaped join.

Reporter: Abhinav Singh (GitHub: OfficialAbhinavSingh)

Affected package ranges reported by GitHub: mem0ai: < 2.0.18 mem0ai: < 3.1.6

Scores and how they were measured

CVSS base severity

6.3

Version 3.1As of

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

Not available

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

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Sources

  1. Primary source

    GitHub-reviewed advisory GHSA-5324-3w58-qpp2 (opens a new tab)

    The public advisory supplies the description, affected package/version ranges, and any listed CVSS metric. GitHub review is not local review.

    Published Checked

  2. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-5324-3w58-qpp2, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 28). Mem0: Cross-tenant conversation leak via unescaped delimiter collision in session-scope key (_build_session_scope) (CVE-2026-116575). https://kevwire.com/record/CVE-2026-116575

MLA

"Mem0: Cross-tenant conversation leak via unescaped delimiter collision in session-scope key (_build_session_scope) (CVE-2026-116575)." KEVWire, 28 Oct. 2026, kevwire.com/record/CVE-2026-116575.

Chicago

KEVWire. "Mem0: Cross-tenant conversation leak via unescaped delimiter collision in session-scope key (_build_session_scope) (CVE-2026-116575)." Last modified October 28, 2026. https://kevwire.com/record/CVE-2026-116575.

Evidence summary (plain text)

Mem0: Cross-tenant conversation leak via unescaped delimiter collision in session-scope key (_build_session_scope) (Oct 28, 2026).
Summary

_build_session_scope() in mem0/memory/main.py builds the conversation-history scope key used to fetch/store the last N raw messages by naively joining caller-supplied user_id/agent_id/run_id values with unescaped & and = delimiters:

def _build_session_scope(filters):
 parts = []
 for key in sorted(["user_id", "agent_id", "run_id"]):
 val = filters.get(key)
 if val:
 parts.append(f"{key}={val}")
 return "&".join(parts)

_validate_and_trim_entity_id() (the only validation applied to these values) rejects only empty/whitespace-only strings — it never forbids & or =.
CVSS 6.3 (version 3.1; evidence as of Oct 28, 2026; https://github.com/advisories/GHSA-5324-3w58-qpp2).
Sources:
GitHub-reviewed advisory GHSA-5324-3w58-qpp2: https://github.com/advisories/GHSA-5324-3w58-qpp2
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc
Record ID: CVE-2026-116575.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 29, 2026, 00:55 UTC. Ingestion is not an independent editorial investigation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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