CVE-2026-55159: CWE-93: Improper Neutralization of CRLF Sequences ('CRLF Injection') in openwrt luci-app-adblock-fast
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.
AI Analysis
Technical Summary
The luci-app-adblock-fast component of OpenWrt versions before 1.2.4-2 contains a CRLF injection vulnerability (CWE-93) in its luci.adblock-fast.setCronEntry RPC method. This method improperly handles carriage-return and line-feed characters in the 'entry' argument, serializing them into the root user's crontab file as if they were a single logical line. An authenticated user with the write ACL for luci-app-adblock-fast can exploit this to create additional physical cron entries running as root, resulting in persistent command execution with UID 0 privileges. The vulnerability does not affect unauthenticated users or those lacking the write ACL. The issue is resolved in version 1.2.4-2.
Potential Impact
Successful exploitation allows an authenticated delegated user with write ACL to execute arbitrary commands persistently as root on the affected system. This can lead to full system compromise, including confidentiality, integrity, and availability impacts. The vulnerability requires authentication and specific permissions, limiting exposure to authorized users only.
Mitigation Recommendations
This vulnerability is fixed in luci-app-adblock-fast version 1.2.4-2. Users should upgrade to version 1.2.4-2 or later to remediate this issue. Until patched, restrict write ACL permissions to trusted users only to minimize risk.
CVE-2026-55159: CWE-93: Improper Neutralization of CRLF Sequences ('CRLF Injection') in openwrt luci-app-adblock-fast
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.
CVSS v3.1
Score 8.8high
Affected software
openwrt
luci-app-adblock-fast
pkg:github/openwrt/luci-app-adblock-fastRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The luci-app-adblock-fast component of OpenWrt versions before 1.2.4-2 contains a CRLF injection vulnerability (CWE-93) in its luci.adblock-fast.setCronEntry RPC method. This method improperly handles carriage-return and line-feed characters in the 'entry' argument, serializing them into the root user's crontab file as if they were a single logical line. An authenticated user with the write ACL for luci-app-adblock-fast can exploit this to create additional physical cron entries running as root, resulting in persistent command execution with UID 0 privileges. The vulnerability does not affect unauthenticated users or those lacking the write ACL. The issue is resolved in version 1.2.4-2.
Potential Impact
Successful exploitation allows an authenticated delegated user with write ACL to execute arbitrary commands persistently as root on the affected system. This can lead to full system compromise, including confidentiality, integrity, and availability impacts. The vulnerability requires authentication and specific permissions, limiting exposure to authorized users only.
Mitigation Recommendations
This vulnerability is fixed in luci-app-adblock-fast version 1.2.4-2. Users should upgrade to version 1.2.4-2 or later to remediate this issue. Until patched, restrict write ACL permissions to trusted users only to minimize risk.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-06-16T15:13:28.165Z
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 6ab1863b55bf5e2cf55cd546
Added to database: 09/21/2026, 19:32:11 UTC
Last enriched: 09/21/2026, 19:46:32 UTC
Last updated: 09/22/2026, 00:29:02 UTC
Views: 9
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