CVE-2026-2869 Overview
A vulnerability has been identified in janet-lang janet up to version 1.40.1. This out-of-bounds read vulnerability affects the function janetc_varset within the file src/core/specials.c of the handleattr Handler component. The manipulation of input leads to an out-of-bounds read condition, which could allow an attacker to access memory locations outside the intended buffer boundaries. The attack requires local access to the system and an exploit has been publicly disclosed.
Critical Impact
Local attackers with low privileges can exploit this out-of-bounds read vulnerability in Janet's compiler component, potentially leading to information disclosure or denial of service through application crashes.
Affected Products
- janet-lang janet versions up to and including 1.40.1
Discovery Timeline
- 2026-02-21 - CVE CVE-2026-2869 published to NVD
- 2026-02-26 - Last updated in NVD database
Technical Details for CVE-2026-2869
Vulnerability Analysis
This vulnerability exists within the janetc_varset function located in src/core/specials.c, which is part of Janet's compiler infrastructure responsible for handling variable assignments. The out-of-bounds read occurs when the handleattr Handler component processes certain malformed or crafted input, allowing the function to read memory beyond the allocated buffer boundaries.
Out-of-bounds read vulnerabilities (CWE-125) typically occur when code reads data past the end, or before the beginning, of the intended buffer. In this case, improper buffer access restrictions (CWE-119) in the memory bounds checking logic enable an attacker to trigger the condition. The vulnerability requires local access and low privileges to exploit, limiting the attack surface to users who already have access to the system.
Root Cause
The root cause stems from improper memory bounds validation in the janetc_varset function within Janet's compiler component. The handleattr Handler fails to properly validate buffer boundaries before accessing memory, leading to the out-of-bounds read condition. This falls under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer) and CWE-125 (Out-of-bounds Read).
Attack Vector
The attack vector is local, meaning an attacker must have local access to the system to exploit this vulnerability. The attack complexity is low and requires low privileges, with no user interaction necessary. Exploitation involves crafting malicious input that triggers the out-of-bounds read condition when processed by Janet's compiler. A proof-of-concept reproduction is available through the GitHub Example Reproduction. The vulnerability manifests when the janetc_varset function processes malformed input through the handleattr Handler, causing it to read beyond the bounds of the allocated memory buffer.
Detection Methods for CVE-2026-2869
Indicators of Compromise
- Unexpected application crashes or segmentation faults when processing Janet scripts
- Abnormal memory access patterns in the Janet interpreter process
- Error messages indicating memory corruption or invalid memory access in src/core/specials.c
Detection Strategies
- Monitor system logs for Janet process crashes or abnormal termination events
- Implement memory sanitizers (AddressSanitizer, Valgrind) during development and testing to catch out-of-bounds reads
- Audit scripts and inputs being processed by Janet for potentially malicious content
Monitoring Recommendations
- Enable core dump collection and analysis for Janet process crashes
- Implement file integrity monitoring on Janet binary and library files
- Monitor for unusual local user activity involving Janet script execution
How to Mitigate CVE-2026-2869
Immediate Actions Required
- Upgrade janet-lang janet to version 1.41.0 or later immediately
- Audit all systems using janet-lang janet to identify vulnerable installations
- Review access controls to limit which users can execute Janet scripts locally
Patch Information
The vulnerability has been addressed in janet-lang janet version 1.41.0. The fix is available through the GitHub Commit Details with identifier 2fabc80151a2b8834ee59cda8a70453f848b40e5. Users should upgrade to version 1.41.0 as documented in the GitHub Release v1.41.0. Additional details about the vulnerability can be found in GitHub Issue #1699.
Workarounds
- Restrict local access to systems running Janet to trusted users only
- Run Janet processes in sandboxed environments to limit potential impact
- Monitor and validate all input being processed by Janet scripts until the patch can be applied
# Upgrade Janet to patched version
git clone https://github.com/janet-lang/janet.git
cd janet
git checkout v1.41.0
make
sudo make install
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
