CVE-2026-77679
Description
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. Fixed upstream in epiphany 50.6 and 49.9 via merge request !2143, which adds ARCHIVE_EXTRACT_SECURE_NODOTDOT and ARCHIVE_EXTRACT_SECURE_SYMLINKS to archive_write_disk_set_options(). Upstream report: https://gitlab.gnome.org/GNOME/epiphany/-/issues/2922
Statement
Red Hat Product Security has determined that this vulnerability does not affect any currently supported Red Hat product. This assessment may evolve based on further analysis and discovery. For more information about this vulnerability and the products it affects, please see the linked references.
Understanding the Weakness (CWE)
Integrity,Confidentiality,Availability
Technical Impact: Execute Unauthorized Code or Commands
The attacker may be able to create or overwrite critical files that are used to execute code, such as programs or libraries.
Integrity
Technical Impact: Modify Files or Directories
The attacker may be able to overwrite or create critical files, such as programs, libraries, or important data. If the targeted file is used for a security mechanism, then the attacker may be able to bypass that mechanism. For example, appending a new account at the end of a password file may allow an attacker to bypass authentication.
Confidentiality
Technical Impact: Read Files or Directories
The attacker may be able read the contents of unexpected files and expose sensitive data. If the targeted file is used for a security mechanism, then the attacker may be able to bypass that mechanism. For example, by reading a password file, the attacker could conduct brute force password guessing attacks in order to break into an account on the system.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
The attacker may be able to overwrite, delete, or corrupt unexpected critical files such as programs, libraries, or important data. This may prevent the product from working at all and in the case of protection mechanisms such as authentication, it has the potential to lock out product users.
Acknowledgements
Red Hat would like to thank Fernando Munoz for reporting this issue.
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