CVE-2026-33699Network attack vector

PDF-processing hang via repeated recovery loop

Published Mar 26, 2026 · Updated Mar 27, 2026

An infinite loop in py-pdf pypdf before 6.9.2 allows attackers to hang PDF processing by supplying a crafted document. DictionaryObject.read_from_stream broadly catches parse errors in non-strict mode and retries after recursion or filter-limit failures without a usable exit path. The crafted file must be read with non-strict parsing, and the resulting loop interrupts the process performing the PDF operation.

CVSS severity7.5
High
EPSS probability0.46%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

An infinite loop in py-pdf pypdf before 6.9.2 allows attackers to hang PDF processing by supplying a crafted document. DictionaryObject.read_from_stream broadly catches parse errors in non-strict mode and retries after recursion or filter-limit failures without a usable exit path. The crafted file must be read with non-strict parsing, and the resulting loop interrupts the process performing the PDF operation.

The record

CVE
CVE-2026-33699
Published
Mar 26, 2026
Updated
Mar 27, 2026
Vendor
py-pdf
Product
pypdf
Classifications
CWE-835, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 26, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 27, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 6.9.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

py-pdf · pypdfversion=< 6.9.2

Published CVSS scores

4.6GitHubCVSS: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
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-835Loop with Unreachable Exit Condition ('Infinite Loop')
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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