vulnerability / NVI-00008987 / Revision 1
Strands Agents: Local Privilege Escalation via Symlink Attack in Default Session File Storage
GitHub lists this reviewed advisory for strands-agents. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
7.1 high
GitHub source severity; exploitability and local consequence require separate evidence.
As of · GitHub Advisory Database
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
strands-agents
source listed< 1.48.0
## Summary The `FileSessionManager` defaults to storing session data in `/tmp/strands/sessions/` (a world-writable directory) using predictable file paths and a write pattern (`open(path + ".tmp", "w")` → `os.replace()`) that follows symbolic links. A local attacker can exploit this to overwrite arbitrary files or inject malicious session data for persistent prompt injection. ## Vulnerability Details **Component:** `strands-py/src/strands/session/file_session_manager.py` **Root Cause:** 1. Default storage directory is `tempfile.gettempdir() + "/strands/sessions/"` (line 58) — resolves to `/tmp/strands/sessions/` on Linux/macOS 2. The `_write_file()` method (lines 116-123) writes to a predictable `.tmp` path without symlink protection: ```python tmp = f"{path}.tmp" with open(tmp, "w", encoding="utf-8", newline="\n") as f: json.dump(data, f, indent=2, ensure_ascii=False) os.replace(tmp, path) ``` 3. `open()` follows symlinks — a pre-placed symlink at the `.tmp` path causes writes to an arbitrary target file 4. No integrity verification (HMAC/signature) on session files — tampered data is loaded as-is ## Attack Vectors ### 1. Arbitrary File Overwrite (Local
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. GitHub Advisory Database
A fixed release is not deployment evidence.
Check current vendor support and compatibility. After making a change, verify the deployed build and relevant runtime conditions. Keep the evidence, owner and time. An updated lockfile alone does not prove what is running.
04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
Each assertion retains its source. Mirrored records may repeat one underlying publisher; additional links are not independent corroboration.
- GHSA-3w55-933p-8pv5 ↗
GitHub Advisory Database · vendor advisory
Observed . GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.
Public revision history
Only published revisions appear here. Routine fetches do not create a material-change event.
- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.