Service interruption via unbounded incremental object cloning
Published Apr 22, 2026 · Updated Apr 22, 2026
Excessive iteration in py-pdf pypdf before 6.10.2 allows attackers to cause long runtimes through crafted PDFs loaded in incremental mode. The PdfWriter.clone_reader_document_root method sizes its object list from the untrusted trailer /Size value and then fetches and replicates every implied object ID. Processing must invoke incremental writing on the malicious file; the resulting CPU and memory work can interrupt the consuming application.
Summary
What happened
Excessive iteration in py-pdf pypdf before 6.10.2 allows attackers to cause long runtimes through crafted PDFs loaded in incremental mode. The PdfWriter.clone_reader_document_root method sizes its object list from the untrusted trailer /Size value and then fetches and replicates every implied object ID. Processing must invoke incremental writing on the malicious file; the resulting CPU and memory work can interrupt the consuming application.
The record
- CVE
- CVE-2026-41313
- Published
- Apr 22, 2026
- Updated
- Apr 22, 2026
- Vendor
- py-pdf
- Product
- pypdf
- Classifications
- CWE-834, T1499.004
- Attack vector
- local
- Privileges
- unauthenticated
Timeline
How it unfolded
- Apr 22, 2026CVE publishedPublication date reported by the CVE source.
- Apr 22, 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.
- Affected versionversion=< 6.10.2
What conditions does exploitation require?
What is affected?
Published CVSS scores
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.
Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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