GHSA-4vvm-4w3v-6mr8 CVE-2023-36464 PYSEC-2026-1835 PYSEC-2026-3008
pypdf and PyPDF2 possible Infinite Loop when a comment isn't followed by a character
- Severity
- 6.2 / 10
- Medium · CVSS 3.1
- Exploit chance (EPSS)
- 0.35%
- Chance of exploitation in the next 30 days. Higher than 28.92% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-835 Loop with Unreachable Exit Condition ('Infinite Loop')
- Fix
- Available
- 2 packages have a fixed version
Description
Impact
An attacker who uses this vulnerability can craft a PDF which leads to an infinite loop if __parse_content_stream is executed. 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 text from such a PDF.
Example Code and a PDF that causes the issue:
from pypdf import PdfReader
# https://objects.githubusercontent.com/github-production-repository-file-5c1aeb/3119517/11367871?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=AKIAIWNJYAX4CSVEH53A%2F20230627%2Fus-east-1%2Fs3%2Faws4_request&X-Amz-Date=20230627T201018Z&X-Amz-Expires=300&X-Amz-Signature=d71c8fd9181c4875f0c04d563b6d32f1d4da6e7b2e6be2f14479ce4ecdc9c8b2&X-Amz-SignedHeaders=host&actor_id=1658117&key_id=0&repo_id=3119517&response-content-disposition=attachment%3Bfilename%3DMiFO_LFO_FEIS_NOA_Published.3.pdf&response-content-type=application%2Fpdf
reader = PdfReader("MiFO_LFO_FEIS_NOA_Published.3.pdf")
page = reader.pages[0]
page.extract_text()
The issue was introduced with https://github.com/py-pdf/pypdf/pull/969
Patches
The issue was fixed with https://github.com/py-pdf/pypdf/pull/1828
Workarounds
It is recommended to upgrade to pypdf>=3.9.0. PyPDF2 users should migrate to pypdf.
If you cannot update your version of pypdf, you should modify pypdf/generic/_data_structures.py:
OLD: while peek not in (b"\r", b"\n"):
NEW: while peek not in (b"\r", b"\n", b""):
Affected versions
PyPI
| Package | Vulnerable | Fixed in |
|---|---|---|
| pypdf | >= 3.1.0, < 3.9.0 |
3.9.0 |
| pypdf2 | >= 2.2.0, <= 3.0.1 |
No fix yet |
| pypdf2 | >= 2.2.0, < 3.9.0 |
3.9.0 |
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
pypdf PyPI → 3.9.0
- pip
pip install --upgrade "pypdf>=3.9.0"- poetry
poetry add "pypdf>=3.9.0"- uv
uv add "pypdf>=3.9.0"
pypdf2 PyPI → 3.9.0
- pip
pip install --upgrade "pypdf2>=3.9.0"- poetry
poetry add "pypdf2>=3.9.0"- uv
uv add "pypdf2>=3.9.0"
Severity breakdown
CVSS 3.1 6.2
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Attack vector
- Local
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Weakness
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.
References
Advisories
Packages
Other links
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-5849-834g-hvw5 pypdf has possible infinite loop when hitting EOF in standard xref table during trailer search | High | Also affects pypdf |
| GHSA-cggf-277g-3q54 pypdf has possible large memory usage when parsing page tree | High | Also affects pypdf |
| GHSA-mfr5-77xh-9j7h pypdf has possible infinite loop when cloning dictionaries | High | Also affects pypdf |
| GHSA-42gh-23hr-vphw pypdf has possible long runtimes when retrieving page labels | High | Also affects pypdf |
| GHSA-4vqv-7265-gm2w pypdf has possible large memory usage for exceptions in strict mode | High | Also affects pypdf |
| GHSA-62m5-6wh8-28x7 pypdf has possible long runtimes/large memory usage for encrypted PDF files | High | Also affects pypdf |
| GHSA-x3rh-gjgm-fmqc pypdf has possible large memory usage when parsing cross-reference streams | High | Also affects pypdf |
| GHSA-jr96-gvgh-j3r4 pypdf: Possible long runtimes for repeated malformed cross-reference entries (Follow-up) | High | Also affects pypdf |
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