OpenWrt luci-app-adblock-fast up to 1.2.4-1 luci.adblock-fast luci.adblock-fast.setCronEntry deserialization

Summaryinfo

A vulnerability marked as very critical has been reported in OpenWrt luci-app-adblock-fast up to 1.2.4-1. Impacted is the function luci.adblock-fast.setCronEntry of the file applications/luci-app-adblock-fast/root/usr/share/rpcd/ucode/luci.adblock-fast. Performing a manipulation of the argument Entry results in deserialization. This vulnerability is reported as CVE-2026-55159. The attack is possible to be carried out remotely. No exploit exists. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in OpenWrt luci-app-adblock-fast up to 1.2.4-1. It has been classified as very critical. This affects the function luci.adblock-fast.setCronEntry of the file applications/luci-app-adblock-fast/root/usr/share/rpcd/ucode/luci.adblock-fast. The manipulation of the argument entry with an unknown input leads to a deserialization vulnerability. CWE is classifying the issue as CWE-502. The product deserializes untrusted data without sufficiently verifying that the resulting data will be valid. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

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.

The advisory is shared at github.com. This vulnerability is uniquely identified as CVE-2026-55159 since 06/16/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. Technical details are known, but no exploit is available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 09/21/2026).

Upgrading to version 1.2.4-2 eliminates this vulnerability.

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Productinfo

Vendor

• OpenWrt

Name

• luci-app-adblock-fast

Version

• 1.2.4-1

CPE 2.3info

• 🔒

CPE 2.2info

• 🔒

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