michaelrsweet Pdfio up to 1.6.4 Dictionary String Formatting stack-based overflow

CVSS Meta Temp Score
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CTI Interest Score
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5.3$0-$5k0.45

Summaryinfo

A vulnerability has been found in michaelrsweet Pdfio up to 1.6.4 and classified as problematic. The affected element is an unknown function of the component Dictionary String Formatting. Performing a manipulation results in stack-based overflow. This vulnerability is reported as CVE-2026-77220. The attack is possible to be carried out remotely. No exploit exists.

Detailsinfo

A vulnerability, which was classified as problematic, was found in michaelrsweet Pdfio up to 1.6.4. This affects an unknown part of the component Dictionary String Formatting. The manipulation with an unknown input leads to a stack-based overflow vulnerability. CWE is classifying the issue as CWE-121. A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function). This is going to have an impact on integrity. The summary by CVE is:

PDFio before 1.6.5 contains a dangling pointer vulnerability in the dictionary string-formatting function that stores a pointer to a stack-local buffer in the document dictionary without copying the string value. In multi-threaded or pooled-request environments, attackers or concurrent users can trigger stack memory reuse across requests, causing cross-tenant document content corruption by silently overwriting one caller's dictionary string values with another caller's data.

The advisory is shared at github.com. This vulnerability is uniquely identified as CVE-2026-77220 since 08/20/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. Neither technical details nor an exploit are publicly available.

Upgrading to version 1.6.5 eliminates this vulnerability.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

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CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA CVSS-B Score: 🔒
CNA CVSS-BT Score: 🔒
CNA Vector: 🔒

CVSSv3info

VulDB Meta Base Score: 5.4
VulDB Meta Temp Score: 5.3

VulDB Base Score: 4.3
VulDB Temp Score: 4.1
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 6.5
CNA Vector (VulnCheck): 🔒

CVSSv2info

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VulDB Base Score: 🔒
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VulDB Reliability: 🔍

Exploitinginfo

Class: Stack-based overflow
CWE: CWE-121 / CWE-119
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Pdfio 1.6.5

Timelineinfo

08/20/2026 CVE reserved
08/21/2026 +1 days Advisory disclosed
08/21/2026 +0 days VulDB entry created
08/21/2026 +0 days VulDB entry last update

Sourcesinfo

Product: github.com

Advisory: github.com
Status: Confirmed

CVE: CVE-2026-77220 (🔒)
GCVE (CVE): GCVE-0-2026-77220
GCVE (VulDB): GCVE-100-394257

Entryinfo

Created: 08/21/2026 23:51
Changes: 08/21/2026 23:51 (76)
Complete: 🔍
Cache ID: 216::103

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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