Not ratedosv:GHSA-763v-5pjm-fx36

    Strands Agents: Default FileSessionManager storage is world-readable on shared systems

    Published Sources: OSV

    What is affected, what to do

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    CVSS v3

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    Severity
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    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

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    30.00 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

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    no public PoC known
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

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    Published

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

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    Handle the vulnerability in regular vulnerability handling under Art. 21(2)(e) NIS2.
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

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    From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

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    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    There is a local confidentiality issue in the default FileSessionManager storage behavior. By default it writes session data under /tmp/strands/sessions and relies on the process umask for directory and file permissions. On systems using the common umask 022, the session directories are 0755 and JSON files are 0644, so other local users can read persisted agent session data.

    This matters on shared developer machines, CI hosts, notebooks, jump boxes, and multi-user GPU servers. Session storage is intended to persist conversation/history/state, so it can contain prompts, model output, tool inputs/outputs, intermediate state, and secrets that pass through the agent.

    Relevant code:

    • strands-py/src/strands/session/file_session_manager.py:58: default storage path is os.path.join(tempfile.gettempdir(), "strands/sessions").
    • strands-py/src/strands/session/file_session_manager.py:118: creates parent directories without a private mode.
    • strands-py/src/strands/session/file_session_manager.py:121: writes JSON files via normal open(..., "w").
    • strands-py/src/strands/session/file_session_manager.py:131: creates session directories without a private mode.

    Local reproduction with umask 022:

    default_storage_dir= /tmp/strands/sessions
0o755 /tmp/strands/sessions
0o755 /tmp/strands/sessions/session_codex_perm_poc
0o644 /tmp/strands/sessions/session_codex_perm_poc/session.json
file_contains_secret= True

    The fixture wrote a fake secret into the session dict to show that sensitive session fields are readable through the resulting file.

    Suggested fixes:

    • Use a private per-user data directory by default rather than /tmp, or create /tmp/strands and descendants with 0700.
    • Write session JSON atomically with 0600 permissions.
    • Consider refusing to use an existing default storage directory if it is not owned by the current user or is group/world accessible.
    • Document that callers should set storage_dir explicitly when they need shared storage.

    This was reproduced on commit dd7b41de38cb.

    Source: OSV (Open Source Vulnerabilities)