CVE-2026-77220Network attack vector

Cross-tenant content corruption via dangling stack pointer

Published Aug 21, 2026 · Updated Aug 21, 2026

Expired pointer dereference in Michael R Sweet PDFio before 1.6.5 allows remote authenticated users to corrupt PDF dictionary data. pdfioDictSetStringf passes its stack-local formatting buffer directly to pdfioDictSetString instead of creating a document-owned string copy. Exploitation requires concurrent use in a multi-threaded or pooled-request application, where stack reuse silently replaces one caller's dictionary values with another caller's data.

CVSS severity7.1
High
EPSS probability0.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Expired pointer dereference in Michael R Sweet PDFio before 1.6.5 allows remote authenticated users to corrupt PDF dictionary data. pdfioDictSetStringf passes its stack-local formatting buffer directly to pdfioDictSetString instead of creating a document-owned string copy. Exploitation requires concurrent use in a multi-threaded or pooled-request application, where stack reuse silently replaces one caller's dictionary values with another caller's data.

The record

CVE
CVE-2026-77220
Published
Aug 21, 2026
Updated
Aug 21, 2026
Vendor
Michael R Sweet
Product
PDFio
Classifications
CWE-825, T1565.001
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 21, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 21, 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=0 <1.6.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Michael R Sweet · PDFioversion=0 <1.6.5

Published CVSS scores

7.1VulnCheckCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
6.5VulnCheckCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N

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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-825Expired Pointer Dereference
T1565.001Stored Data Manipulation

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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