CVE-2026-107734: Input Validation Flaw

Description

SumatraPDF is a multi-format reader for Windows. In 3.5.2 and earlier, an attacker-controlled SyncTeX source filename is substituted for the %f placeholder in an external editor command line without safe Windows argument quoting, and the resulting command line is passed to CreateProcessW(). A user with an external editor configured or auto-detected who opens a PDF with a crafted .synctex.gz file and invokes inverse search can inject command-line flags; the resulting impact depends on the target editor interpreting those flags and can include unintended editor actions or code execution through a malicious extension. No broader impact is claimed beyond the advisory-supported conditions. No fixed version is available as of this review.

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Weakness Type (CWE)

CWE-20 Improper Input Validation

CWE-88 CWE-88

References

Other References

https://github.com/sumatrapdfreader/sumatrapdf/commit/398d23624362c60722d9709173a287ea53545b3b https://github.com/sumatrapdfreader/sumatrapdf/security/advisories/GHSA-jf4v-rw66-j4w2

Frequently Asked Questions

What is CVE-2026-107734? +

SumatraPDF is a multi-format reader for Windows. In 3.5.2 and earlier, an attacker-controlled SyncTeX source filename is substituted for the %f placeholder in an external editor command line without safe Windows argument quoting, and the resulting command line is passed to CreateProcessW(). A user with an external editor configured or auto-detected who opens a PDF with a crafted .synctex.gz file and invokes inverse search can inject command-line flags; the resulting impact depends on the target editor interpreting those flags and can include unintended editor actions or code execution through a malicious extension. No broader impact is claimed beyond the advisory-supported conditions. No fixed version is available as of this review.

How do I check if I'm vulnerable to CVE-2026-107734? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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