Uncontrolled Memory Allocation in Loki - CVE-2026-21729
Published: July 16, 2026 / Updated: July 24, 2026
Vulnerability identifier: #VU139270
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-21729
CWE-ID: CWE-789
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Grafana Labs
Affected software:
Loki
Loki
Detailed vulnerability description
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to uncontrolled memory allocation in the detected_fields endpoint when processing a user-supplied limit query parameter. A remote attacker can send a specially crafted request with a massive limit value to cause a denial of service.
The issue can trigger out-of-memory conditions even when there are no matching results.
How to mitigate CVE-2026-21729
Install security update from vendor's website.