Summary
Echo: Decompress permits unbounded gzip expansion in v4
Affected versions and patch
Echo v4 versions through v4.16.0 are affected. Upgrade to v4.16.1.
The patch adds DecompressConfig.MaxDecompressedSize, defaulting to 100 MiB when zero. A value of -1 explicitly disables the limit. Reading beyond the cap returns ErrStatusRequestEntityTooLarge (HTTP 413), including through JSON and XML binding. Bodies exactly at the configured limit remain valid. Streaming enforcement requires callers to handle body-read errors.
Workarounds
Disable gzip request decompression on exposed routes, or place BodyLimit after Decompress so the application limit applies to decoded bytes. Apply suitable request deadlines and concurrency limits as well.
Credits
Reported by @q490107865. The exact-limit behavior incorporates @Shubham-Padkonde's work in #3136.
Impact
Echo v4's opt-in Decompress middleware exposed a gzip-decoded request stream without limiting its expanded size. A small compressed request could therefore produce a very large decoded body. Handlers that read or bind that body could consume excessive memory or CPU, and repeated or concurrent requests could cause denial of service.
The middleware is not enabled by default. A limit on the compressed request size alone does not bound the decompressed size. Applications that already apply an effective body limit after decompression have reduced exposure.
Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2026-118261? CVE-2026-118261 is a high-severity uncontrolled resource consumption vulnerability in github.com/labstack/echo/v4 (go), affecting versions >= 4.0.0, < 4.16.1. It is fixed in 4.16.1. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
- Which versions of github.com/labstack/echo/v4 are affected by CVE-2026-118261? github.com/labstack/echo/v4 (go) versions >= 4.0.0, < 4.16.1 is affected.
- Is there a fix for CVE-2026-118261? Yes. CVE-2026-118261 is fixed in 4.16.1. Upgrade to this version or later.
- Is CVE-2026-118261 exploitable, and should I be worried? Whether CVE-2026-118261 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-118261 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-118261? Upgrade
github.com/labstack/echo/v4to 4.16.1 or later.