PYSEC-2026-3533

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Import Source
https://github.com/pypa/advisory-database/blob/main/vulns/praisonaiagents/PYSEC-2026-3533.yaml
JSON Data
https://api.osv.dev/v1/vulns/PYSEC-2026-3533
Aliases
Published
2026-07-23T11:41:41.087045Z
Modified
2026-07-23T15:00:23.528381836Z
Severity
  • 6.5 (Medium) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N CVSS Calculator
Summary
PraisonAI: execute_code sandbox bypass: str.format C-level attribute access reads every blocklisted dunder
Details

Summary

The execute_code tool's subprocess sandbox advertises a three-layer defense (AST validation, text-pattern blocklist, restricted __builtins__). In sandbox mode (the default) only two layers are active — the text-pattern blocklist is skipped — and both remaining layers are bypassed by combining two CPython semantics:

  1. Runtime string assembly. The AST validator (src/praisonai-agents/praisonaiagents/tools/python_tools.py:75) enumerates blocked dunder names against ast.Attribute.attr, ast.Call.func.id, and ast.Constant string-substring. Names assembled at runtime (e.g. "_"*2 + "class" + "_"*2) appear in the AST as multiple short ast.Constant nodes, none containing a blocked substring, so the static check passes.
  2. C-level attribute access via format-spec. str.format / str.format_map resolve dotted field references through CPython's internal PyObject_GetAttr (do_string_format → get_field). This C path never consults the Python-level getattr binding. The sandbox's _safe_getattr wrapper (python_tools.py:221) is installed only as the getattr name in safe_builtins, so any C-level attribute access — including format-spec field resolution — sidesteps it. format/format_map are also absent from _SANDBOX_BLOCKED_CALLS (python_tools.py:56).

Combined, this yields an arbitrary read primitive over every blocklisted attribute (__class__, __qualname__, __bases__, __base__, function __globals__, __dict__, …).

Affected code

| File | Lines | Symbol | Role | |---|---|---|---| | src/praisonai-agents/praisonaiagents/tools/python_tools.py | 39–54 | _SANDBOX_BLOCKED_ATTRS | The blocklist the bypass renders unreachable | | src/praisonai-agents/praisonaiagents/tools/python_tools.py | 56–60 | _SANDBOX_BLOCKED_CALLS | Missing entries: format, format_map | | src/praisonai-agents/praisonaiagents/tools/python_tools.py | 75–102 | _validate_code_ast | Static check, blind to runtime string assembly | | src/praisonai-agents/praisonaiagents/tools/python_tools.py | 221–226 | _safe_getattr | Wraps Python-level getattr only; C-level access bypasses | | src/praisonai-agents/praisonaiagents/tools/python_tools.py | 352 | execute_code | Entry point; gated by @require_approval(risk_level="critical") |

Reproducer

import os
os.environ["PRAISONAI_AUTO_APPROVE"] = "true"
from praisonaiagents.tools.python_tools import execute_code

payload = '''
und = "_" * 2                         # "__" assembled at runtime
key1 = und + "class" + und            # "__class__"
key2 = und + "qualname" + und         # "__qualname__"
fmt_class = "{0." + key1 + "}"
fmt_qual2 = "{0." + key1 + "." + key2 + "}"
print("LEAK_CLASS=" + fmt_class.format(()))
print("LEAK_QUAL2=" + fmt_qual2.format(()))
'''
print(execute_code(payload, sandbox_mode="sandbox", timeout=15))

Observed: stdout = LEAK_CLASS=<class 'tuple'> / LEAK_QUAL2=tuple, success: true, no security error. Both __class__ (one hop) and __class__.__qualname__ (two hops) — all blocklisted — are read.

Trust boundary

The @require_approval(risk_level="critical") gate is bypassed when PRAISONAI_AUTO_APPROVE is set (verified: require_approval short-circuits on is_env_auto_approve()). That variable is set by the project's FULL_AUTO autonomy mode, the bots-CLI launchers, and the project's own issue-triage CI workflow — postures where the agent reaches execute_code with no human approval. The payload then arrives via any LLM-visible surface (user message, retrieved document, tool/web/MCP output) and the tool-call machinery passes it as the code argument.

Relationship to GHSA-4mr5-g6f9-cfrh

The code's own comment at python_tools.py:46 cites GHSA-4mr5-g6f9-cfrh, which added __self__ to the blocklist to stop C-builtins leaking builtins via func.__self__. This finding does not bypass that single entry — it bypasses the entire blocklist, because format-spec attribute resolution never consults the blocklist or _safe_getattr. "{0.__self__}".format(print) would leak __self__ regardless of the blocklist. Same defense surface, different mechanism; the GHSA-4mr5 fix does not mitigate this.

Scope (read primitive only)

This reports the read primitive. Turning the read into in-process execution requires a callable bridge; the obvious one (string.Formatter().get_field() returning the live object) is not directly reachable because import string is blocked at the AST layer (no ast.Import). Other bridges may exist; a full execution chain is not claimed here. If one is found, severity rises to ~8.8 (the subprocess has no seccomp/setrlimit/syscall filtering).

Suggested fix

  1. Add format, format_map to _SANDBOX_BLOCKED_CALLS (blocks the calls at the AST layer; cost: also blocks benign str.format).
  2. Or replace str in safe_builtins with a subclass whose format/format_map reject dotted fields resolving to leading-underscore attributes (preserves benign formatting).
  3. Or drop sandbox-mode's in-process security claim and document that real isolation requires external sandboxing (gVisor/firejail/container/microVM) — which matches what the subprocess provides today.

The text-pattern blocklist present in the direct path (python_tools.py:487-502) is absent from the sandbox path; even if added, the runtime-assembly trick defeats it, so (1) or (2) is required.

Reporter: Kai Aizen / SnailSploit — kai@snailsploit.com — PGP on request. Coordinated disclosure; no public posting.

References

Affected packages

PyPI / praisonaiagents

Package

Name
praisonaiagents
View open source insights on deps.dev
Purl
pkg:pypi/praisonaiagents

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected
Fixed
1.6.59

Affected versions

0.*
0.0.1
0.0.2
0.0.3
0.0.4
0.0.5
0.0.6
0.0.7
0.0.8
0.0.9
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0.0.11
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0.0.14
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0.0.192
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0.0.194
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0.0.199
0.1.0
0.1.1
0.1.2
0.1.3
0.1.4
0.1.5
0.1.6
0.1.7
0.1.8
0.1.9
0.1.10
0.1.11
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0.1.25
0.1.26
0.1.27
0.2.0
0.2.1
0.2.2
0.3.0
0.3.1
0.3.2
0.3.3
0.3.4
0.4.0
0.4.1
0.5.0
0.5.1
0.5.2
0.5.3
0.6.0
0.6.1
0.6.2
0.6.3
0.6.4
0.6.5
0.6.6
0.6.7
0.6.8
0.7.0
0.7.1
0.8.0
0.8.1
0.9.0
0.9.1
0.10.0
0.10.1
0.10.2
0.10.3
0.10.4
0.10.5
0.10.6
0.10.7
0.10.8
0.10.9
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0.11.0
0.11.1
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0.11.31
0.12.0
0.12.1
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0.13.0
0.13.1
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0.14.0
0.14.1
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0.14.3
0.14.4
0.14.5
0.14.6
0.14.7
0.14.8
0.14.9
0.14.10
0.14.11
0.14.12
0.14.14
0.14.15
0.14.16
0.15.0
0.15.1
0.15.2
0.15.3
1.*
1.0.0
1.1.0
1.2.0
1.2.1
1.2.2
1.2.3
1.2.4
1.3.0
1.3.1
1.4.0
1.4.1
1.4.2
1.4.3
1.4.4
1.4.5
1.4.6
1.4.7
1.4.8
1.5.0
1.5.1
1.5.2
1.5.3
1.5.5
1.5.6
1.5.7
1.5.8
1.5.9
1.5.10
1.5.11
1.5.12
1.5.13
1.5.14
1.5.15
1.5.16
1.5.17
1.5.18
1.5.19
1.5.20
1.5.21
1.5.22
1.5.23
1.5.24
1.5.25
1.5.26
1.5.27
1.5.28
1.5.29
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1.5.31
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1.5.33
1.5.34
1.5.35
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1.5.128
1.5.129
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1.5.132
1.5.133
1.5.134
1.5.135
1.5.136
1.5.137
1.5.138
1.5.139
1.5.140
1.5.141
1.5.142
1.5.143
1.5.144
1.5.145
1.5.146
1.5.147
1.5.148
1.5.149
1.6.1
1.6.2
1.6.3
1.6.4
1.6.5
1.6.6
1.6.7
1.6.8
1.6.9
1.6.10
1.6.11
1.6.12
1.6.13
1.6.14
1.6.15
1.6.16
1.6.17
1.6.18
1.6.19
1.6.20
1.6.21
1.6.22
1.6.23
1.6.24
1.6.25
1.6.26
1.6.27
1.6.28
1.6.29
1.6.30
1.6.31
1.6.32
1.6.33
1.6.34
1.6.35
1.6.36
1.6.37
1.6.38
1.6.39
1.6.40
1.6.41
1.6.42
1.6.43
1.6.44
1.6.45
1.6.46
1.6.47
1.6.48
1.6.50
1.6.51
1.6.52
1.6.53
1.6.54
1.6.55
1.6.56
1.6.57
1.6.58

Database specific

source 
"https://github.com/pypa/advisory-database/blob/main/vulns/praisonaiagents/PYSEC-2026-3533.yaml"