GHSA-hm9v-vj3r-r55m is a medium-severity (CVSS 6.2) CWE-835 vulnerability in pypdf2. 2 public exploit references exist, so weaponization risk is real. A fix is available for pypdf2 — see the affected versions and patch details below.
PyPDF2 vulnerable to possible Infinite Loop when reading malformed objects
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for GHSA-hm9v-vj3r-r55m.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-hm9v-vj3r-r55m plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,636 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
pypdf2Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
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:
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
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
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | pypdf2 | ≥ 2.10.5&&< 2.10.6 | 2.10.6pip install --upgrade 'pypdf2==2.10.6' |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for pypdf2, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update pypdf2 to 2.10.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-hm9v-vj3r-r55m is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-hm9v-vj3r-r55m can be triaged on real exposure rather than presence alone.
Tailored to GHSA-hm9v-vj3r-r55m. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-hm9v-vj3r-r55m in your dependencies?
O3 Security finds GHSA-hm9v-vj3r-r55m across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.