CVE-2026-48156

Processing delay via zero-width cross-reference entries

Published May 28, 2026 · Updated May 28, 2026

Excessive iteration in pypdf before 6.12.0 allows attackers to cause long PDF-parsing runtimes via a crafted cross-reference stream. In _sanitize_pdf15_xref_stream_index_pairs(), a zero-only /W array is clamped to one byte per entry, so a large attacker-controlled /Size drives iteration over nonexistent cross-reference entries. The condition is reached when an application parses the crafted PDF and can occupy its processing thread for an extended period without affecting confidentiality or integrity.

CVSS severity5.1
Medium
EPSS probability0.12%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Excessive iteration in pypdf before 6.12.0 allows attackers to cause long PDF-parsing runtimes via a crafted cross-reference stream. In _sanitize_pdf15_xref_stream_index_pairs(), a zero-only /W array is clamped to one byte per entry, so a large attacker-controlled /Size drives iteration over nonexistent cross-reference entries. The condition is reached when an application parses the crafted PDF and can occupy its processing thread for an extended period without affecting confidentiality or integrity.

The record

CVE
CVE-2026-48156
Published
May 28, 2026
Updated
May 28, 2026
Vendor
py-pdf
Product
pypdf
Classifications
CWE-834, T1499.004
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 28, 2026CVE publishedPublication date reported by the CVE source.
  2. May 28, 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=< 6.12.0

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

py-pdf · pypdfversion=< 6.12.0

Published CVSS scores

5.1GitHubCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
3.3PyPA Advisory DatabaseCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L

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)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-834Excessive Iteration
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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