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CVE-2026-54531· NVD / CVE Program· CNA GitHub_M

pypdf: Possible infinite loop when processing outlines/bookmarks in writer

pypdf is a free and open-source pure-python PDF library. Prior to 6.13.0, an attacker who uses this vulnerability can craft a PDF which leads to an infinite loop. This requires merging a file with outlines into a writer. This vulnerability is fixed in 6.13.0.

MediumCVSS 6.9 · v4.0—No exploit Fix available
Published
Jun 22, 2026
Updated
Jun 25, 2026
EPSS
0.2% · 6th percentile
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Report tools

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Action score

27

Monitor

Low priority for now.

CVSS
27 / 40 · 6.9 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.2%

CISA SSVC decision

Exploitation
none
Automatable
yes
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · GitHub_M
6.9
NVD has not scored this yet; the score shown is the CNA’s.

CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Affected systems

VendorProduct
pypdf projectpypdf

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • pypdf project pypdfbefore 6.13.0

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

  • py-pdf pypdf

    • < 6.13.0affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12pypdfall versions—
Debian:12pypdf2all versions—
PyPIpypdfbefore 6.13.06.13.0

Same product

pypdf project: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-59936pypdf: Possible infinite loop for not terminated inline images
    34Monitor
  • CVE-2026-59935pypdf: Possible infinite loop for not terminated inline images (ASCII85 and ASCIIHex filter)
    34Monitor
  • CVE-2026-59938pypdf: Possible large memory usage for wrong image dimensions
    27Monitor
  • CVE-2026-59937pypdf: Possible long runtimes for repeated malformed cross-reference entries
    27Monitor
  • CVE-2026-57204pypdf: Missing stream length values ignore defined limits
    27Monitor
  • CVE-2026-54651pypdf: Possible infinite loop when processing threads/articles in writer
    27Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
py-pdf pypdf6.13.0 · descriptionVendor (CNA)
PyPI:pypdf6.13.0Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-5993516 days apartpypdf: Possible infinite loop for not terminated inline images (ASCII85 and ASCIIHex filter)
    34Monitor
  • CVE-2026-545300 days apartpypdf: Possible infinite loop when retrieving fonts for layout-mode text extraction
    27Monitor
  • CVE-2026-546510 days apartpypdf: Possible infinite loop when processing threads/articles in writer
    27Monitor
  • CVE-2026-27024122 days apartpypdf has a possible infinite loop when processing TreeObject
    27Monitor
  • CVE-2026-24688146 days apartpypdf has possible Infinite Loop when processing outlines/bookmarks
    20Monitor
  • CVE-2026-3369988 days apartpypdf: Possible infinite loop during recovery attempts in DictionaryObject.read_from_stream
    18Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
Integrity
Availability
Attack vector
Local
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
X

Weakness class (CWE)

CWE-835 · Loop with Unreachable Exit Condition ('Infinite Loop')

CVSS vector

CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/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:X

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Noroxi analysis

No Noroxi analysis for this record yet

We don't hand-write analysis for all 385,000+ vulnerabilities; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.

We use this product, ask for help

Change log

  1. Fix✗ → ✓

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References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records