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Link Following (Symlink)Weakness · CWE-59

CVE-2026-12503

CRITICAL · 9.2 CVSS v4.0 Published 2026-07-24
No fix yet
No fix has been published. The vendor has not shipped a fixed release or patch. You remain exposed.
See remediation →
94/100
Remediation priority · Urgent
Zero-click 4 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Improper Link Resolution (CWE-59) in `/usr/bin/larm_starter` in Loytec L-INX, L-GATE, L-ROC, L-IOB, L-DALI, L-VIS and L-PAD through 8.4.16 on LINX-A64 allows an authenticated `larmapp` attacker to make `/etc/passwd` writable by the `larmapp` group (leading to root privilege escalation) via a symlink attack on `/etc/lighttpd/ssl/server.pem`.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis
How this class of weakness works · CWE-59

A file operation follows a symbolic link without checking where it actually points, so an attacker who can plant or swap a link redirects the operation to a file they should not be able to touch. It is a common local privilege-escalation primitive. Remediation is resolving and validating the real target path, and avoiding operations on attacker-controllable links.

General guidance for the link following (symlink) class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
High
Authentication
X
User interaction
None
Scope
X

CVSS:4.0/AV:L/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Recommended fix Moderate confidence

Firmware version greater than 8.4.16 (e.g., 8.4.17 or later - check Loytec support for exact fixed release)

  1. 1. Identify the exact Loytec device model (L-INX, L-GATE, L-ROC, L-IOB, L-DALI, L-VIS, or L-PAD) and current firmware version using the web interface or CLI
  2. 2. Access the Loytec support portal at www.loytec.com and navigate to the firmware download section
  3. 3. Download the latest available firmware version for your specific device model
  4. 4. Review the firmware release notes to confirm the version includes a fix for CVE-2026-12503 (CWE-59 symlink vulnerability in larm_starter)
  5. 5. Back up current device configuration through the web interface or backup functionality
  6. 6. Upload and install the new firmware via the device's web interface or CLI firmware update function
  7. 7. After firmware update, verify the vulnerability is resolved by confirming /etc/lighttpd/ssl/server.pem is no longer writable by the larmapp group
  8. 8. Restore configuration from backup if needed
Caveat Review release notes for your specific device model for any configuration or feature changes between current version and new version

Generated from the published advisory — verify against the referenced sources before acting.

No vendor fix exists The vendor has not published a patch for this.

There is no version to upgrade to and no patch to apply. Every affected install stays exposed until the vendor ships a fix — or somebody else builds one.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-12503 in production — separate from our analysis above.

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