CVE-2023-36807: Infinite Loop when reading malformed objects in pypdf
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/datastructures.py::readobject.
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.readfromstream(stream, pdf) else: return NumberObject.readfromstream(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.readfromstream(stream, pdf) else: return NumberObject.readfromstream(stream) else: raise PdfReadError( f"Invalid Elementary Object starting with {tok} @{stream.tell()}" )
References pypdf issue #1329 pypdf PR #1331
Other sources
pypdf is a pure-python PDF library capable of splitting, merging, cropping, and transforming the pages of PDF files. In version 2.10.5 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. Versions prior to 2.10.5 throw an error, but do not hang forever. This issue was fixed with https://github.com/py-pdf/pypdf/pull/1331 which has been included in release 2.10.6. Users are advised to upgrade. Users unable to upgrade should modify PyPDF2/generic/datastructures.py::readobject to an an error throwing case. See GHSA-hm9v-vj3r-r55m for details.
— MITRE
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
pip/PyPDF2to a version that resolves this vulnerability.Fixed in 2.10.6 - Upgrade
Upgrade
pypdfto a version that resolves this vulnerability.Fixed in 2.10.6Patch pypdf PR #1331 - Upgrade
Upgrade
pypdfto a version that resolves this vulnerability.Fixed in 3.1.0 - Configuration
If you cannot update, modify `PyPDF2/generic/_data_structures.py::read_object` to an error-throwing case to avoid the infinite loop when reading malformed PDFs (issue: Infinite Loop when reading malformed objects in pypdf).
PyPDF2/pypdf (pypdf/pypdf) PyPDF2/generic/_data_structures.py::read_object = Modify read_object to an error-throwing case instead of looping on malformed objects (e.g., for the IndirectPattern path, throw PdfReadError rather than continuing to read/loop)
Event History
Frequently Asked Questions
What is the impact of CVE-2023-36807?
This vulnerability can cause an infinite loop in a PDF, which can use 100% of a CPU core.
How does CVE-2023-36807 affect the affected software?
The affected software can be blocked by a crafted PDF, causing an infinite loop.
What versions of PyPDF2 are affected by CVE-2023-36807?
PyPDF2 version 2.10.5 is affected by this vulnerability.
How can I fix CVE-2023-36807?
Update to PyPDF2 version 2.10.6 to fix this vulnerability.
Where can I find more information about CVE-2023-36807?
You can find more information about CVE-2023-36807 on the GitHub security advisory page and the NIST vulnerability detail page.