CVE-2026-63729 TeX Live vulnerability
The SyncTeX parser (synctex_parser.c) shipped with TeX Live and embedded by downstream consumers such as GNOME Evince contains a heap use-after-free vulnerability that allows attackers to crash applications or potentially execute arbitrary code by supplying a malformed .synctex or .synctex.gz file. A malformed SyncTeX file can construct a ref node with a NULL parent pointer, causing the replacement routine to fail to detach the node from its sibling chain, which triggers recursive freeing of live tree nodes and leaves dangling pointers that are later accessed by the parser during document load.
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TeX Live should be reviewed and updated if it matches the affected versions. The recommended fix is to apply the vendor-supported patched version or the mitigation steps below, then retest the public website with Fixnx.
Who is affected
Affected versions
- <= TeX Live 2025
Fixed versions
- TeX Live 2026
How to fix it
CVE-2026-63729 affects TeX Live and involves code or command execution. Successful exploitation may let an attacker run unintended code or operating-system commands in the affected process. Prioritize deployments that process untrusted input, expose the affected feature, or hold sensitive data. Upgrade to TeX Live 2026 or a downstream package that includes the SyncTeX parser fix.
- Inventory every deployment, device, package, plugin, container, build, and environment that uses TeX Live.
- Compare the installed version with the recorded affected range: <= TeX Live 2025.
- Upgrade to TeX Live 2026 or a downstream package that includes the SyncTeX parser fix.
- Until patched, disable the affected feature, limit untrusted input, and run the service with the lowest practical privileges.
- Review configuration, roles, tokens, network paths, and exposed endpoints connected to TeX Live; remove access that is not required.
- Review process, shell, web, audit, and network logs for unexpected commands, child processes, downloads, callbacks, or changed files.
- If exploitation is suspected, isolate affected assets, preserve evidence, rotate exposed credentials or keys, restore trusted data, and rebuild compromised systems before returning them to service.
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Verify the fix
- Confirm every affected asset now runs the fixed vendor-supported release or has the documented mitigation for CVE-2026-63729 in place.
- Use a safe regression test to confirm the affected code or command execution path no longer produces the vulnerable behavior.
- Confirm temporary access controls, endpoint restrictions, network blocks, and least-privilege settings remain effective after the update.
- Review post-remediation logs and rerun Fixnx plus the relevant package, dependency, firmware, browser, or product-specific security check.
- Document affected assets, versions, changes, validation evidence, reviewed logs, and any credential rotation, cleanup, or replacement completed.
Related categories
Related security risks
More published guidance from the same primary category.
Trusted references
FAQ
What is affected by CVE-2026-63729?
TeX Live versions listed as affected should be reviewed: <= TeX Live 2025.
What should I fix first?
Start with internet-facing sites, admin panels, login flows, plugins, themes, modules, packages, and systems that process user-controlled input or sensitive data.
How do I confirm the fix worked?
Apply the patched version or mitigation, clear caches where relevant, retest the affected workflow, and run a new Fixnx scan to verify public website exposure signals.
How are Fixnx security risk categories chosen?
Fixnx keeps one canonical risk page and assigns only broad, relevant categories such as ecosystem, technology area, or vulnerability class.