Raw vector
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:XCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
Summary
CVE-2026-33699 is a medium-severity Infinite Loop (CWE-835) vulnerability in Pypdf Project Pypdf. Its CVSS base score is 4.6 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Application or System Exploitation (T1499.004); ranked at the 38th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SI-2 (Flaw Remediation) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-33699 is a denial-of-service vulnerability (CWE-835: Loop with Unreachable Exit Condition) affecting the pypdf library, a free and open-source pure-Python PDF processing tool. Versions prior to 6.9.2 are vulnerable when processing a specially crafted PDF file in non-strict mode, which triggers an infinite loop during file reading. The issue has a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H), highlighting its potential for high-impact availability disruption without requiring authentication or user interaction.
An attacker can exploit this vulnerability remotely by supplying a malicious PDF to any application or service that uses a vulnerable version of pypdf in non-strict mode for PDF parsing. Successful exploitation leads to an infinite loop, causing the affected process to hang or consume excessive resources, resulting in denial of service. No privileges are needed, and the attack requires low complexity, making it accessible to remote unauthenticated actors targeting PDF-handling workflows.
The vulnerability has been addressed in pypdf version 6.9.2, as detailed in the project's release notes and security advisory (GHSA-87mj-5ggw-8qc3). Users unable to upgrade immediately can manually apply the fix from the corresponding pull request. Security practitioners should audit dependencies for vulnerable pypdf versions and enforce strict parsing mode where feasible to mitigate exposure.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-16496
Vulnerability Data
pypdf is a free and open-source pure-python PDF library. Versions prior to 6.9.2 have a vulnerability in which an attacker can craft a PDF which leads to an infinite loop. This requires reading a file in non-strict mode. This has…
more
been fixed in pypdf 6.9.2. If users cannot upgrade yet, consider applying the changes from the patch manually.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Developer testing and evaluation can discover unreachable loop exit conditions through static analysis, fuzzing, or execution tracing.
Flaw remediation processes identify and correct infinite-loop defects reported from testing or operations.
Requiring documented development processes and secure coding standards reduces introduction of loops whose termination conditions are unreachable.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing can uncover infinite-loop conditions before release.
Secure development life cycle mandates practices that can detect and prevent infinite-loop defects.
Application security requirements can specify loop-termination rules, indirectly reducing the weakness.
Secure coding standards directly address loop termination and prevent infinite loops.