📖 ~4 min read • Source: Debian Security Tracker
Related CVEs: CVE-2017-1000047
Upstream summary: rbenv (all current versions) is vulnerable to Directory Traversal in the specification of Ruby version resulting in arbitrary code execution
Table of contents
Symptom & Impact
rbenv on Debian 13 runs only when something invokes it, so there is no crash loop and no failed unit to notice — the exposure is input-driven. A developer build, a CI job, a package rebuild or triage tooling that runs objdump, readelf or gdb across an untrusted binary can hit a malformed section header and corrupt memory inside the toolchain process, running code as the build user. On a shared builder or CI runner that means tampered build output rather than downtime. rbenv is a build-time developer tool that exits when the command finishes, so there is no unit to restart — only in-flight builds and long-lived helpers such as distcc or clangd still hold the old binaries.
Environment & Reproduction
Reproduction targets Debian 13. Confirm release with cat /etc/debian_version and lsb_release -a, and the currently installed package with dpkg -l rbenv and apt-cache policy rbenv. Capture system state with sudo reportbug rbenv if you need to file upstream. Trigger the workflow that exposes rbenv while collecting journalctl -b, /var/log/apt/history.log, and dpkg -l output.
Root Cause Analysis
Root cause is tracked at Debian Security Tracker. The Debian Security Team shipped fixes in the corresponding rbenv point release for Debian 13; running an outdated build leaves the host exposed to the failure modes referenced above. Correlate journalctl --since with apt history (/var/log/apt/history.log) and any kernel taint flags in /proc/sys/kernel/tainted to isolate the originating change.
Quick Triage
Quick triage: sudo apt update && apt list --upgradable, sudo nft list ruleset (or sudo iptables -L), and sudo dpkg --audit. For kernel issues review journalctl -k --since "1 hour ago".
Step-by-Step Diagnosis
1) systemctl --failed. 2) journalctl -xe and . 3) Validate firewall: sudo nft list ruleset or sudo iptables -L -n -v. 4) dpkg -V rbenv for integrity. 5) sudo apt install --reinstall rbenv if files were tampered. 6) Correlate findings with /var/log/apt/history.log, /var/log/dpkg.log, and Debian Security Tracker to pin the change that introduced the regression.
Solution – Primary Fix
Primary fix: apply the corrective apt transaction documented in Debian Security Tracker. Typical commands: sudo apt update, sudo apt -y install --only-upgrade rbenv (or sudo unattended-upgrade -v), then dpkg -l rbenv to validate the new build is installed. For kernel advisories add sudo reboot.
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Solution – Alternative Approaches
Alternatives include pinning a known-good version via /etc/apt/preferences.d/rbenv.pref, holding the package with sudo apt-mark hold rbenv, rolling back with sudo apt install rbenv=<old-version>, switching firewall backends between iptables-legacy and nftables via update-alternatives --config iptables, or applying the patch from the security archive only — deb debian-13-security main contrib non-free — while delaying the full point-release upgrade.
Verification & Acceptance Criteria
Acceptance: dpkg -l rbenv shows the expected fixed version is active shows no errors, apt list --upgradable no longer lists the advisory, sudo nft list ruleset matches the intended policy, and the original reproduction steps for rbenv no longer trigger the failure across two consecutive runs.
Rollback Plan
Capture state with apt list --installed > /root/apt-pre.txt and dpkg --get-selections > /root/dpkg-pre.txt. To revert, run sudo apt install --allow-downgrades rbenv=<old-version> and reload . Reboot if the kernel or initramfs changed and re-verify symptoms. Where LVM snapshots are in use, sudo lvconvert --merge /dev/<vg>/preupgrade is the fastest rollback path.
Prevention & Hardening
Prevent recurrence by enabling unattended-upgrades with Unattended-Upgrade::Origins-Pattern tuned to origin=Debian,codename=${distro_codename},label=Debian-Security, subscribing to debian-security-announce, mirroring through a local apt-mirror or aptly repo for controlled rollouts, version-locking sensitive packages, and monitoring file integrity with debsums -c or aide --check. Apply CIS Debian hardening and keep needrestart installed so service restarts happen automatically after library upgrades.
Related Errors & Cross-Refs
Related issues that commonly surface alongside rbenv: apt lock contention (dpkg --configure -a), systemd unit ordering cycles, firewall rule drift, and kernel taint flags in cat /proc/sys/kernel/tainted. See sibling common-problem articles in this Debian 13 series for adjacent failure modes.
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Browse all common problems & solutions on the Tutorials Hub.
References & Further Reading
Primary reference: Debian Security Tracker. Supporting docs: Debian Administrators Handbook, man apt, man systemctl, man nft, man iptables, man journalctl, man debsums, the Debian Security Tracker at security-tracker.debian.org, and Debian Security FAQ at debian.org/security/faq. Review /usr/share/doc/rbenv/ for component-level notes implicated in rbenv.
