CVE-2026-77220
PDFio < 1.6.5 Dangling Pointer via Dictionary String-Formatting
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.
Fixes and workarounds
Fix
The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches.
Source: CNA: VulnCheckAffected products and versions
| Product | Versions | Authority |
|---|---|---|
| pdfio michaelrsweet michaelrsweet/pdfio
github |
≥ 0; < 1.6.5 (affected, semver)
Other versions: affected |
CNA: VulnCheck |
Version ranges are source assertions. Check the vendor advisory and your installed configuration before determining exposure.
CVSS assessments
| Version / score | Vector | Authority |
|---|---|---|
| 4.0 / 7.1 high |
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N | CNA: VulnCheck |
| 3.1 / 6.5 medium |
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N | CNA: VulnCheck |
Exploit evidence
No exploit evidence in collected sources. This is not proof of no exploitation.
References
- https://github.com/michaelrsweet/pdfio/releases/tag/v1.6.5CNA: VulnCheck · release-notes
- https://github.com/michaelrsweet/pdfio/commit/22b9afc800c5833f9e851e35938972bd4c76a357CNA: VulnCheck · patch
- https://www.vulncheck.com/advisories/pdfio-dangling-pointer-via-dictionary-string-formattingCNA: VulnCheck · third-party-advisory
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