CVE-2023-36807: PyPDF2 PyPDF2 Vulnerable To Possible Infinite Vulnerability

MODERATE
Advisory Identifier: GHSA-hm9v-vj3r-r55m
Share
CVSS 6.2
CWE-835
Published
Advisory Summary

CVE-2023-36807 is a MODERATE (CVSS 6.2) pypdf2 vulnerable to possible infinite vulnerability (CWE-835: Loop with Unreachable Exit Condition ('Infinite Loop')) affecting PyPDF2 libraries in the PyPI ecosystem. The issue involves pypdf2 vulnerable to possible infinite loop when reading malformed objects. Remediation is available by upgrading affected packages to version 2.10.6.

CVE-2023-36807 at a Glance

CVE Identifier CVE-2023-36807
GHSA Identifier GHSA-hm9v-vj3r-r55m
Severity MODERATE
CVSS v3.1 Base Score 6.2
CWE Classification CWE-835: Loop with Unreachable Exit Condition ('Infinite Loop')
Affected Product PyPDF2
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 6.2

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).

Attack Vector Local (AV:L)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity None (I:N)
Availability High (A:H)

How to Fix CVE-2023-36807

To remediate this vulnerability, upgrade all affected PyPDF2 dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

PyPDF2 fixed: 2.10.6 
pip install PyPDF2>=2.10.6
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show PyPDF2

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2023-36807, inspect your installed packages using pip:

pip show PyPDF2

Analyze the terminal output to locate any version of PyPDF2 in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 2.10.6), your application is affected.

Note: The pip show PyPDF2 command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-835: Loop with Unreachable Exit Condition ('Infinite Loop'), where the product contains an iteration or loop with an exit condition that cannot be reached, i.e., an infinite loop. In PyPDF2, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Impact An attacker who uses this vulnerability can craft a PDF which leads to an infinite loop. This infinite loop blocks the current process and can utilize a single core of the CPU by 100%. It does not affect memory usage. That is, for example, the case if the user extracted metadata from such a malformed PDF. ### Patches The issue was fixed with https://github.com/py-pdf/pypdf/pull/1331 ### Workarounds If you cannot update your version of `PyPDF2` (preferably to `pypdf>3.1.0` as PyPDF2 is deprecated), you should modify `PyPDF2/generic/_data_structures.py::read_object`. Replace: ```python else: # number object OR indirect reference peek = stream.read(20) stream.seek(-len(peek), 1) # reset to start if IndirectPattern.match(peek) is not None: return IndirectObject.read_from_stream(stream, pdf) else: return NumberObject.read_from_stream(stream) ``` by ```python elif tok in b"0123456789+-.": # number object OR indirect reference peek = stream.read(20) stream.seek(-len(peek), 1) # reset to start if IndirectPattern.match(peek) is not None: return IndirectObject.read_from_stream(stream, pdf) else: return NumberObject.read_from_stream(stream) else: raise PdfReadError( f"Invalid Elementary Object starting with {tok} @{stream.tell()}" ) ``` ### References * [pypdf issue #1329](https://github.com/py-pdf/pypdf/issues/1329) * [pypdf PR #1331](https://github.com/py-pdf/pypdf/pull/1331)

CVE-2023-36807 Affected PyPDF2 Versions

1 component(s)
Fixed Versions:
2.10.6
Product / Package Ecosystem Affected Versions Fixed Version
PyPDF2
pypi/PyPDF2
PyPI
≥ 2.10.5
< 2.10.6
All 1 versions
2.10.5
2.10.6

References

GitHub Advisory / Wiki ADVISORY
https://github.com/py-pdf/pypdf/security/advisories/GHSA-hm9v-vj3r-r55m
NVD — CVE-2023-36807 NVD
https://nvd.nist.gov/vuln/detail/CVE-2023-36807
PyPDF2 Source Repository REPOSITORY
https://github.com/py-pdf/pypdf/issues/1329
PyPDF2 Source Repository REPOSITORY
https://github.com/py-pdf/pypdf/pull/1331
Security Fix Commit FIX COMMIT
https://github.com/py-pdf/pypdf/commit/e6531a25325e7e0174b6a1ba03b57320b5227f6b
PyPDF2 Source Repository REPOSITORY
https://github.com/py-pdf/pypdf

Frequently Asked Questions

What is CVE-2023-36807?
CVE-2023-36807 is a security vulnerability in PyPDF2 involving PyPDF2 vulnerable to possible Infinite Loop when reading malformed objects under CWE-835: Loop with Unreachable Exit Condition ('Infinite Loop').
Which PyPDF2 versions are affected?
Affected versions include releases prior to 2.10.6 across affected packages: PyPDF2.
What version fixes CVE-2023-36807?
Upgrading to 2.10.6 (or the latest patched release for your respective branch) resolves the vulnerability.
Is PyPDF2 affected?
Yes, PyPDF2 is affected in releases prior to 2.10.6. Upgrade your dependency to 2.10.6 or later.
What is the CVSS score of CVE-2023-36807?
CVE-2023-36807 has a CVSS v3.1 base score of 6.2 (MODERATE) with vector string CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2023-36807?
CVE-2023-36807 is classified under CWE-835: Loop with Unreachable Exit Condition ('Infinite Loop') (The product contains an iteration or loop with an exit condition that cannot be reached, i.e., an infinite loop.).
How can I check PyPI dependencies for CVE-2023-36807?
Run the dependency tree command: 'pip show PyPDF2'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-hm9v-vj3r-r55m",
  "modified" : "2023-06-30T22:19:39Z",
  "published" : "2023-06-30T22:19:39Z",
  "aliases" : [ "CVE-2023-36807" ],
  "summary" : "PyPDF2 vulnerable to possible Infinite Loop when reading malformed objects",
  "details" : "### Impact\nAn attacker who uses this vulnerability can craft a PDF which leads to an infinite loop.\nThis infinite loop blocks the current process and can utilize a single core of the CPU by 100%. It does not affect memory usage. That is, for example, the case if the user extracted metadata from such a malformed PDF.\n\n### Patches\nThe issue was fixed with https://github.com/py-pdf/pypdf/pull/1331\n\n### Workarounds\nIf you cannot update your version of `PyPDF2` (preferably to `pypdf>3.1.0` as PyPDF2 is deprecated), you should modify `PyPDF2/generic/_data_structures.py::read_object`.\n\nReplace:\n\n```python\n    else:\n        # number object OR indirect reference\n        peek = stream.read(20)\n        stream.seek(-len(peek), 1)  # reset to start\n        if IndirectPattern.match(peek) is not None:\n            return IndirectObject.read_from_stream(stream, pdf)\n        else:\n            return NumberObject.read_from_stream(stream)\n```\n\nby\n\n```python\n    elif tok in b\"0123456789+-.\":\n        # number object OR indirect reference\n        peek = stream.read(20)\n        stream.seek(-len(peek), 1)  # reset to start\n        if IndirectPattern.match(peek) is not None:\n            return IndirectObject.read_from_stream(stream, pdf)\n        else:\n            return NumberObject.read_from_stream(stream)\n    else:\n        raise PdfReadError(\n            f\"Invalid Elementary Object starting with {tok} @{stream.tell()}\"\n        )\n```\n\n### References\n* [pypdf issue #1329](https://github.com/py-pdf/pypdf/issues/1329)\n* [pypdf PR #1331](https://github.com/py-pdf/pypdf/pull/1331)",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "PyPDF2"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.10.5"
      }, {
        "fixed" : "2.10.6"
      } ]
    } ],
    "versions" : [ "2.10.5" ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/py-pdf/pypdf/security/advisories/GHSA-hm9v-vj3r-r55m"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2023-36807"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/py-pdf/pypdf/issues/1329"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/py-pdf/pypdf/pull/1331"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/py-pdf/pypdf/commit/e6531a25325e7e0174b6a1ba03b57320b5227f6b"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/py-pdf/pypdf"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-835" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2023-06-30T22:19:39Z",
    "nvd_published_at" : "2023-06-30T19:15:09Z"
  }
}