CVE-2026-55159luci-app-adblock-fast: Delegated `luci-app-adblock-fast` users can reach root command execution by injecting newline-separated cron entries

Description

luci-app-adblock-fast a WebUI for fast, lightweight DNS-based ad-blocker for OpenWrt that works with dnsmasq, smartdns, or unbound. Prior to 1.2.4-2, the luci.adblock-fast.setCronEntry RPC method accepts an entry argument containing carriage-return or line-feed characters and serializes it into /etc/crontabs/root as though it were one logical line. An authenticated delegated user with the luci-app-adblock-fast write ACL can therefore create an additional physical root cron entry through applications/luci-app-adblock-fast/root/usr/share/rpcd/ucode/luci.adblock-fast, resulting in persistent command execution as UID 0 when cron runs. The issue is not demonstrated for unauthenticated callers or users without the component write ACL. This vulnerability is fixed in 1.2.4-2.

Data: CVE.org, NVD, CISA KEV, FIRST EPSS, Ubuntu. Published as the sources state it, in English.

Affected products and versions

References and patches

• https://github.com/openwrt/luci/security/advisories/GHSA-ggpf-xrph-wg5v
• https://github.com/openwrt/luci/pull/8705
• https://github.com/openwrt/luci/commit/9ccd99b5898457e5ef39dc21aea226d7fb6e5c7e
• https://github.com/openwrt/luci/commit/f67461fd0255bf992b2b559c22ec288067f2f9da