CVE-2026-53941: Inspektor Gadget DOS Vulnerability

CVE-2026-53941 Overview

CVE-2026-53941 is a denial-of-service vulnerability in Inspektor Gadget, an eBPF-based data collection and system inspection framework for Kubernetes clusters and Linux hosts. The flaw resides in the uprobe library resolver, which parses /etc/ld.so.cache files supplied by containers when a uprobe-based gadget is active. An unprivileged container can supply a crafted cache file that forces excessive iteration and quadratic string concatenation in the parser. Because pkg/container-hook holds the fanotify container-start pause while parsing occurs, the abuse delays new container startup by roughly a minute, blocks Docker from starting other containers, and degrades monitoring. Affected versions range from 0.27.0 through 0.53.0, with a fix in 0.53.1.

Critical Impact
An unprivileged container can consume excessive CPU and block startup of other containers on the host, degrading monitoring and workload availability.

Affected Products

Inspektor Gadget versions 0.27.0 through 0.53.0
Kubernetes clusters and Linux hosts running affected Inspektor Gadget versions with an active uprobe-based gadget
Docker environments monitored by vulnerable Inspektor Gadget deployments

Discovery Timeline

2026-09-15 - CVE-2026-53941 published to NVD
2026-09-16 - Last updated in NVD database

Technical Details for CVE-2026-53941

Vulnerability Analysis

The vulnerability is an uncontrolled resource consumption issue ([CWE-770]) in the ld.so.cache parser used by Inspektor Gadget's uprobe tracer. The parser in pkg/uprobetracer/ldcache_parser.go trusts the attacker-controlled EntryCount field and iterates over it without bounding the work performed. It computes cache1Len using uint32 arithmetic that can overflow, and then repeatedly invokes readStringFromBytes in pkg/uprobetracer/bytes.go. That helper performs byte-by-byte immutable string concatenation, producing quadratic runtime relative to input size.

During parsing, pkg/container-hook holds the fanotify container-start pause. A crafted cache in a newly starting container therefore stalls the container-start path itself, preventing Docker from launching other containers and degrading gadget monitoring for the duration of the parse. Caches from already-running containers can still burn CPU but do not block new-container startup. The advisory establishes no confidentiality or integrity impact; the issue is availability-only.

Root Cause

The root cause is twofold: unvalidated trust in the EntryCount header field, and an inefficient string-building routine used inside a hot loop. binary.Read-based deserialization with reflection compounded the cost, while overflowing uint32 size math allowed the parser to iterate structures that far exceed the actual buffer.

Attack Vector

An unprivileged container writes a crafted /etc/ld.so.cache file into its own filesystem before starting. When a uprobe-based gadget is active on the host, Inspektor Gadget's container hook parses the file during the fanotify start-pause. The parser enters the pathological code path, burning CPU and holding the pause for approximately one minute per malicious container start.

// Patch excerpt from pkg/uprobetracer/bytes.go
// Source: https://github.com/inspektor-gadget/inspektor-gadget/commit/2ca55021acf675b65040beff2a5ec348054be782

import (
    "bytes"
    "errors"
    "unsafe"
)

// plainDataStruct constrains types to fixed-size structs containing only
// numeric fields (int32, uint32, uint64, fixed-size arrays of int8, etc.).
// These types have no pointers, strings, slices, or interfaces, making them
// safe to reinterpret directly from a byte buffer without serialization.
type plainDataStruct interface {
    ldCache1 | ldCache1Entry | ldCache2 | ldCache2Entry
}

// reinterpretBytes interprets rawData as a value of type T using direct memory
// reinterpretation (equivalent to a C memcpy/cast). This is used instead of
// encoding/binary.Read for performance: binary.Read uses reflection and
// allocates intermediate buffers, significantly slower when called in tight
// loops (e.g., parsing ~700K ld.so.cache entries).
func reinterpretBytes[T plainDataStruct](obj *T, rawData []byte) error {
    if int(unsafe.Sizeof(*obj)) != len(rawData) {
        return errors.New("reading from bytes: length mismatched")
    }
    // ...
}

The patch replaces reflection-based binary.Read with direct memory reinterpretation for fixed-size structs, and constrains parsing work to what the buffer actually holds. See the GitHub commit and Pull Request #5547 for the full diff.

Detection Methods for CVE-2026-53941

Indicators of Compromise

Container start operations that stall for approximately 60 seconds while an uprobe-based gadget is active
Sustained high CPU usage in the Inspektor Gadget process correlated with new container creation events
Docker daemon reporting delays or failures to start additional containers on hosts running vulnerable Inspektor Gadget versions

Detection Strategies

Inventory Inspektor Gadget deployments and flag any node running versions 0.27.0 through 0.53.0 with uprobe gadgets enabled
Correlate fanotify container-start pause duration with per-container CPU consumption to identify containers triggering the parser
Inspect container image build artifacts for unusual or oversized /etc/ld.so.cache files that do not match glibc-generated caches

Monitoring Recommendations

Alert on Inspektor Gadget process CPU spikes exceeding baseline during container-start events
Monitor Docker and container runtime logs for repeated container-start latency anomalies
Track Kubernetes pod scheduling latency on nodes where uprobe-based gadgets are attached

How to Mitigate CVE-2026-53941

Immediate Actions Required

Upgrade Inspektor Gadget to version 0.53.1 or later on all Kubernetes clusters and Linux hosts
Audit any deployment running versions between 0.27.0 and 0.53.0 and prioritize nodes running uprobe-based gadgets
Restrict which workloads can run on nodes with active uprobe gadgets until the upgrade completes

Patch Information

The fix is available in Inspektor Gadget Release v0.53.1. Technical details are documented in GitHub Security Advisory GHSA-vjhx-2cqw-3q6q. The patch replaces the reflection-based parser with typed memory reinterpretation and constrains iteration to the actual buffer length.

Workarounds

Disable uprobe-based gadgets on hosts that cannot be upgraded immediately
Prevent untrusted or multi-tenant workloads from starting on nodes where Inspektor Gadget is monitoring with uprobe gadgets
Use admission controls to reject container images that ship non-standard /etc/ld.so.cache files

bash

# Verify Inspektor Gadget version on a Kubernetes cluster
kubectl get pods -n gadget -o jsonpath='{.items[*].spec.containers[*].image}'

# Upgrade to the patched release (Helm example)
helm repo update
helm upgrade gadget inspektor-gadget/gadget \
  --namespace gadget \
  --version 0.53.1