Pdfly: pypdf: Possible infinite loop when processing threads/articles in writer (CVE-2026-54651)
A vulnerability in pdfly's pypdf component allows an attacker to craft a PDF that causes an infinite loop when merging files containing threads or articles. This can lead to denial of service by resource exhaustion. The issue has been fixed in pypdf version 6.13.1. Users unable to upgrade immediately can apply the changes from the referenced pull request as a workaround.
AI Analysis
Technical Summary
CVE-2026-54651 describes a vulnerability in the pdfly product's pypdf library where processing PDFs with threads or articles during a merge operation can cause an infinite loop. This flaw can be triggered by an attacker supplying a specially crafted PDF file, leading to a denial of service condition. The vulnerability affects versions of pdfly from 0.4.0 up to but not including 0.5.1_21. The issue is addressed by an official patch in pypdf version 6.13.1, which resolves the infinite loop condition.
Potential Impact
An attacker can cause a denial of service by triggering an infinite loop in the pdfly pypdf writer when merging PDFs containing threads or articles. This results in resource exhaustion and potential application hang or crash. There is no indication of privilege escalation, data disclosure, or code execution.
Mitigation Recommendations
Upgrade to pypdf version 6.13.1 or later to apply the official fix. If immediate upgrade is not possible, apply the changes from pull request #3839 as a temporary workaround to mitigate the infinite loop issue.
Pdfly: pypdf: Possible infinite loop when processing threads/articles in writer (CVE-2026-54651)
Description
A vulnerability in pdfly's pypdf component allows an attacker to craft a PDF that causes an infinite loop when merging files containing threads or articles. This can lead to denial of service by resource exhaustion. The issue has been fixed in pypdf version 6.13.1. Users unable to upgrade immediately can apply the changes from the referenced pull request as a workaround.
CVSS v4.0
Affected software
Run on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-54651 describes a vulnerability in the pdfly product's pypdf library where processing PDFs with threads or articles during a merge operation can cause an infinite loop. This flaw can be triggered by an attacker supplying a specially crafted PDF file, leading to a denial of service condition. The vulnerability affects versions of pdfly from 0.4.0 up to but not including 0.5.1_21. The issue is addressed by an official patch in pypdf version 6.13.1, which resolves the infinite loop condition.
Potential Impact
An attacker can cause a denial of service by triggering an infinite loop in the pdfly pypdf writer when merging PDFs containing threads or articles. This results in resource exhaustion and potential application hang or crash. There is no indication of privilege escalation, data disclosure, or code execution.
Mitigation Recommendations
Upgrade to pypdf version 6.13.1 or later to apply the official fix. If immediate upgrade is not possible, apply the changes from pull request #3839 as a temporary workaround to mitigate the infinite loop issue.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- BREW-pdfly-CVE-2026-54651
- Osv Schema Version
- 1.7.3
- Ecosystems
- ["Homebrew"]
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6ac1396ca43b0b3b89d5fdd9
Added to database: 10/03/2026, 17:20:44 UTC
Last enriched: 10/03/2026, 17:26:05 UTC
Last updated: 10/04/2026, 02:46:05 UTC
Views: 6
Community Reviews
0 reviewsCrowdsource mitigation strategies, share intel context, and vote on the most helpful responses. Sign in to add your voice and help keep defenders ahead.
Want to contribute mitigation steps or threat intel context? Sign in or create an account to join the community discussion.
Actions
Updates to AI analysis require Pro Console access. Upgrade inside Console → Billing.
Need more coverage?
Upgrade to Pro Console for AI refresh and higher limits.
For incident response and remediation, OffSeq services can help resolve threats faster.
Latest Threats
Check if your credentials are on the dark web
Instant breach scanning across billions of leaked records. Free tier available.