CVE-2026-102620 Overview
CVE-2026-102620 is a signed integer overflow vulnerability in Freedesktop Poppler versions 26.06.0, 26.07.0, and 26.08.0. The flaw resides in the FoFiTrueType::cvtSfnts function within fofi/FoFiTrueType.cc at line 1210. An attacker with local access and low privileges can trigger the overflow during TrueType font processing. The issue is classified as [CWE-189] Numeric Errors and requires local access to exploit. A public proof-of-concept has been disclosed, and the Poppler maintainers have released commit 245d3c6823377755f2c1d5fdddd010279c6ed94d to address the issue.
Critical Impact
Local integer overflow in Poppler's TrueType font converter may cause limited integrity impact when processing crafted PDF or font input.
Affected Products
- Freedesktop Poppler 26.06.0
- Freedesktop Poppler 26.07.0
- Freedesktop Poppler 26.08.0
Discovery Timeline
- 2026-09-29 - CVE-2026-102620 published to the National Vulnerability Database
- 2026-09-29 - Last updated in NVD database
Technical Details for CVE-2026-102620
Vulnerability Analysis
The vulnerability affects Poppler, the widely used PDF rendering library that underpins document viewers such as Evince, Okular, and various headless PDF processing pipelines. The defect exists in FoFiTrueType::cvtSfnts, a routine that converts TrueType font tables into PostScript sfnts arrays for embedding during rendering. During this conversion, arithmetic on signed integer values can wrap around when specific font table sizes are supplied. The resulting overflow produces incorrect length or offset computations that downstream code relies on for buffer handling. Exploitation requires the attacker to supply a malformed font, typically embedded in a PDF, that the vulnerable Poppler process opens locally.
Root Cause
The root cause is unchecked signed integer arithmetic in fofi/FoFiTrueType.cc around line 1210. Values derived from attacker-controlled font table fields are combined without validating that the results remain within the representable range of a signed integer. Once wraparound occurs, subsequent size checks pass with corrupted values, undermining the safety invariants that protect memory operations.
Attack Vector
The attack vector is local. An adversary with low privileges on the system must convince a user or automated pipeline to open a crafted PDF or font file with a Poppler-based tool. Because the CVSS 4.0 vector indicates no confidentiality or availability impact and only limited integrity impact, the practical outcome is corruption of processed font data rather than direct code execution. The exploit code has been publicly disclosed, increasing the likelihood of opportunistic use in fuzzing pipelines or targeted document workflows.
No verified proof-of-concept code is reproduced here. Refer to the GitHub CVE Integer Overflow Report for the disclosed technical details.
Detection Methods for CVE-2026-102620
Indicators of Compromise
- Unexpected crashes or sanitizer reports in processes linked against libpoppler when opening PDF documents that embed TrueType fonts.
- PDF files containing malformed TrueType font tables with abnormally large or negative size fields designed to trigger overflow in cvtSfnts.
- Local invocation of Poppler command-line utilities such as pdftops or pdftocairo on untrusted files by unprivileged users.
Detection Strategies
- Inventory installed Poppler versions across Linux workstations and servers, flagging any host running 26.06.0, 26.07.0, or 26.08.0.
- Enable AddressSanitizer or UndefinedBehaviorSanitizer builds of Poppler in test environments to surface overflow conditions during document ingestion.
- Correlate process telemetry for Poppler-based tools invoked with input paths outside standard user document directories.
Monitoring Recommendations
- Monitor package management logs to confirm timely deployment of the patched Poppler build across the fleet.
- Alert on repeated abnormal terminations of PDF rendering processes, which may indicate exploitation attempts against unpatched hosts.
- Track file provenance for PDF documents processed by server-side rendering services and quarantine those originating from untrusted sources.
How to Mitigate CVE-2026-102620
Immediate Actions Required
- Apply the upstream Poppler fix from commit 245d3c6823377755f2c1d5fdddd010279c6ed94d or upgrade to a distribution package that incorporates it.
- Restrict local execution of Poppler-based utilities on shared systems to trusted users until patches are deployed.
- Review server-side PDF processing pipelines that rely on Poppler and validate that inputs are sanitized or sandboxed.
Patch Information
The Poppler project addressed the issue in upstream commit 245d3c6823377755f2c1d5fdddd010279c6ed94d, merged via GitLab Poppler Merge Request 2326. Additional context is available in GitLab Poppler Work Item 1762 and the VulDB CVE-2026-102620 entry. Rebuild any statically linked applications after updating the Poppler library.
Workarounds
- Run PDF rendering workloads inside a sandbox such as bubblewrap, firejail, or a container to limit the impact of malformed font parsing.
- Disable automatic PDF preview features in file managers on affected hosts until the patched Poppler package is installed.
- Reject inbound documents containing malformed or unusually large TrueType font tables at email and file transfer gateways.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
