CVE-2025-47276 Overview
CVE-2025-47276 affects Actualizer, a single shell script solution that lets developers and embedded engineers build Debian operating systems. Versions prior to 1.2.0 use OpenSSL's -passwd function, which generates SHA-512 password hashes instead of a modern memory-hard algorithm such as yescrypt or argon2i. Every Debian OS image produced by an affected Actualizer build inherits these weaker hashes for the root and alpha accounts. An attacker who obtains /etc/shadow from a deployed system can crack the hashes faster than against Debian's default yescrypt-protected accounts.
Critical Impact
Deployed Debian images contain weakly hashed credentials for root and alpha, enabling offline password cracking if /etc/shadow is exposed.
Affected Products
- Actualizer versions prior to 1.2.0
- Debian operating system images built using affected Actualizer releases
- root and alpha user accounts on deployed systems
Discovery Timeline
- 2025-05-13 - CVE-2025-47276 published to NVD
- 2026-04-15 - Last updated in NVD database
Technical Details for CVE-2025-47276
Vulnerability Analysis
Actualizer automates Debian image creation through a shell script. During provisioning, it sets the initial passwords for the root and alpha accounts by calling OpenSSL's -passwd subcommand. OpenSSL's passwd utility supports only legacy algorithms, and Actualizer selected SHA-512 ($6$). SHA-512 is a fast, general-purpose hash without memory hardness or tunable cost suitable for password storage. Modern Debian releases default to yescrypt ($y$) in /etc/shadow, which is significantly more resistant to GPU and ASIC-accelerated cracking. The categorization aligns with [CWE-328: Use of Weak Hash].
Root Cause
The defect is a cryptographic algorithm choice rather than a code execution flaw. OpenSSL's passwd command intentionally lacks support for memory-hard schemes, as documented in the upstream OpenSSL discussion. By delegating password hashing to OpenSSL, Actualizer bypassed Debian's PAM-driven yescrypt configuration and stored credentials with a faster-to-crack hash.
Attack Vector
Exploitation requires an attacker to obtain the shadow file from a deployed image, for example through a separate file disclosure issue, backup theft, lost device, or post-compromise lateral movement. Once obtained, the SHA-512 hashes are cracked offline using tools such as hashcat (mode 1800) or john, recovering plaintext passwords that may be reused across the fleet. The vulnerability does not grant initial access on its own but degrades the confidentiality of stored credentials.
# Patch reference: APP_VERSION bump in Shell/debian-minbase-install.sh
-APP_VERSION="1.1.0"
+APP_VERSION="1.2.0"
# Source: https://github.com/ChewKeanHo/Actualizer/commit/32c9cc232c856f078f8269fba80ce7562bbff86b
# The 1.2.0 release replaces OpenSSL -passwd with Debian's yescrypt-backed
# password setting path so new accounts are stored as $y$ rather than $6$.
Detection Methods for CVE-2025-47276
Indicators of Compromise
- Entries in /etc/shadow for root or alpha beginning with $6$ on systems built by Actualizer.
- Image build logs referencing Actualizer APP_VERSION1.1.0 or earlier.
- Unexpected successful SSH or console authentications to root or alpha from external networks.
Detection Strategies
- Audit /etc/shadow across the Debian fleet and flag accounts where the hash prefix is $6$ instead of $y$.
- Inventory build pipelines for invocations of openssl passwd and Actualizer scripts predating 1.2.0.
- Correlate authentication telemetry with accounts known to have been provisioned by affected Actualizer versions.
Monitoring Recommendations
- Alert on shadow file reads by non-root processes and on backup jobs that export /etc/shadow outside trusted storage.
- Monitor for repeated authentication failures against root and alpha indicating credential-cracking attempts.
- Track CI/CD job outputs to ensure rebuilt images use Actualizer 1.2.0 or later.
How to Mitigate CVE-2025-47276
Immediate Actions Required
- Upgrade Actualizer to version 1.2.0 and rebuild any in-flight Debian images.
- On already deployed systems, manually reset the root and alpha passwords so Debian's yescrypt hasher replaces the SHA-512 entries.
- Rotate any credentials that may have been reused across images derived from affected Actualizer builds.
Patch Information
The fix is delivered in Actualizer 1.2.0, which removes the OpenSSL -passwd invocation in Shell/debian-minbase-install.sh so account creation uses Debian's native yescrypt-backed hasher. See the GitHub Release Version 1.2.0, the GitHub Security Advisory GHSA-v626-chv9-v9qr, and the GitHub Commit Details for the patch contents.
Workarounds
- Reset both root and alpha passwords on existing deployments using passwd so the new hash is written by yescrypt.
- Restrict access to /etc/shadow and image artifacts containing it until accounts are migrated.
- Disable direct root SSH login and enforce key-based authentication on the alpha account.
# Force re-hashing of root and alpha credentials with Debian's yescrypt
sudo passwd root
sudo passwd alpha
# Verify new hashes use the $y$ (yescrypt) prefix instead of $6$ (SHA-512)
sudo awk -F: '$1=="root" || $1=="alpha" {print $1, substr($2,1,3)}' /etc/shadow
# Confirm PAM is configured to use yescrypt for future password changes
grep -E '^password.*pam_unix' /etc/pam.d/common-password
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
