CVE-2026-77620 in Vector
Summary
by MITRE • 09/22/2026
Vector is a high-performance observability data pipeline. From 0.15.0 until 0.57.0, the logstash source feeds each decompressed frame back into its decoder without limiting nested compression depth. An unauthenticated remote peer that can reach the default 0.0.0.0:5044 listener can send many nested compressed frames, causing recursive decoding that exhausts the worker thread stack and aborts the process. The same nested construction amplifies decompressed input, and process termination can halt log ingestion for every tenant on a shared pipeline. This issue is fixed in version 0.57.0.
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Analysis
by VulDB Data Team • 09/22/2026
The vulnerability identified within Vector versions ranging from 0.15.0 to 0.57.0 represents a critical resource exhaustion flaw inherent in the logstash source component of this high-performance observability data pipeline. The core technical deficiency lies in the handling of compressed input streams, specifically regarding nested compression layers. When the system receives data via the Logstash Forwarder protocol on the default listener port 5044 bound to all network interfaces at 0.0.0.0, it initiates a decompression process for each incoming frame. However, the implementation fails to enforce any limit or depth check on nested compression structures. This architectural oversight allows an attacker to craft payloads containing deeply nested compressed frames that are recursively fed back into the decoder without termination conditions based on nesting depth.
From a technical perspective, this flaw triggers unbounded recursion during the decompression phase. Each layer of compression requires stack space for decoding operations, and because there is no mechanism to detect or halt excessive nesting levels, the recursive calls continue until the worker thread's call stack is completely exhausted. This results in a stack overflow condition that causes the Vector process to abort abruptly. The vulnerability classifies under CWE-675, which describes operations with multiple independent inputs without adequate mutual exclusion and specifically relates to insufficient depth limits for nested structures such as compression or encryption layers. It also aligns with CWE-400 regarding uncontrolled resource consumption, where an attacker can trigger a denial of service by consuming system resources beyond intended limits through recursive processing logic errors.
The operational impact of this vulnerability is severe due to the shared nature of many observability pipelines. Since Vector often processes logs for multiple tenants or applications within a single instance, the termination of one worker thread process does not merely affect a single data stream but can halt log ingestion for every tenant relying on that pipeline. This creates a broad denial-of-service scenario where critical monitoring and logging capabilities are suspended across an entire organization's infrastructure. An unauthenticated remote peer with network access to port 5044 can exploit this by sending specially crafted nested compressed frames, effectively taking down the observability platform without needing valid credentials or prior authentication.
In terms of threat modeling, this vulnerability is exploitable remotely and requires no user interaction beyond network connectivity to the target service. It maps directly to MITRE ATT&CK technique T1498, Network Denial of Service, specifically under the sub-technique of Resource Exhaustion via Recursive Processing or similar mechanisms that lead to system instability. The attack vector is classified as remote with low complexity and requires no privileges for exploitation, making it a high-severity risk in any environment where Vector is exposed to untrusted networks on port 5044.
Mitigation strategies primarily involve upgrading the Vector installation to version 0.57.0 or later, which includes patches that enforce depth limits on nested compression operations and prevent the recursive stack overflow condition. For environments unable to upgrade immediately, network-level controls should be implemented to restrict access to port 5044 exclusively to trusted internal subnets or specific source IP addresses known for legitimate log forwarding activity. Additionally, deploying a reverse proxy with rate limiting can help mitigate volumetric attacks that attempt to trigger the vulnerability through high-frequency requests. Monitoring logs for sudden process restarts of Vector instances may also serve as an early detection mechanism for exploitation attempts in unpatched systems.