Medium [CVE-2026-77679] path traversal in WebExtension XPI extraction (ZIP slip)
This medium-severity Red Hat Linux advisory covers CVE-2026-77679.
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Summary
A path traversal (ZIP slip) vulnerability exists in Epiphany when installing WebExtension packages from.xpi files. In src/webextension/ephy-web-extension-manager.c, the decompress_xpi_thread() function extracts XPI archives (ZIP format) to disk using libarchive.
For each archive entry, the output path is built by concatenating the intended extraction directory with the raw pathname from the archive: full_path = g_build_filename(path, archive_entry_pathname(entry), NULL); archive_entry_set_pathname(entry, full_path); ret = archive_write_header(ext, entry); The libarchive extraction options did not include ARCHIVE_EXTRACT_SECURE_NODOTDOT or ARCHIVE_EXTRACT_SECURE_SYMLINKS.
As a result, archive entries containing parent-directory traversal sequences (for example "../../../../../.bashrc") are written outside the intended web_extensions extraction directory.
A malicious.xpi file can therefore overwrite arbitrary files writable by the user running Epiphany, such as ~/.bashrc, ~/.config/autostart/*.desktop, or ~/.ssh/authorized_keys. This can lead to persistent code execution on subsequent shell startup or GNOME login.
Exploitation requires the victim to install or open a crafted.xpi file. The reporter notes that opening an XPI can trigger extraction even when the WebExtensions feature is not enabled by default.
Affected versions: Epiphany >= 47.rc.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 59 minutes ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 59 minutes ago·verify at source
Mitigation checklist
- Upgrade to epiphany 50.6, 49.9, or later. Do not install untrusted .xpi WebExtension packages until patched.
Official advisory · high-confidence parse· fetched 59 minutes ago·verify at source
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