How severe is CVE-2026-118261?

No CVSS score has been assigned to CVE-2026-118261 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-118261?

CVE-2026-118261 affects the following packages: github.com/labstack/echo/v4 (Go). Ecosystems affected: Go.

How do I fix CVE-2026-118261?

Update github.com/labstack/echo/v4 to 4.16.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-118261 is resolved across your whole dependency graph.

How do I detect CVE-2026-118261 in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/labstack/echo/v4, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-118261 if there is no patch (or I can't update yet)?

Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Is CVE-2026-118261 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-118261 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-118261?

CVE-2026-118261 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 31th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-118261?

CVE-2026-118261 is classified as Uncontrolled Resource Consumption (CWE-400), CWE-409 (CWE-409). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-118261 published, and has it been updated?

CVE-2026-118261 was published on October 28, 2026 and was last updated on October 29, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹 Go

Not in CISA KEV

CVE-2026-118261 — echo

Fix: labstack/echo@3fb0ba7

CVE-2026-118261 is a Uncontrolled Resource Consumption vulnerability in github.com/labstack/echo/v4. A fix is available for github.com/labstack/echo/v4 — see the affected versions and patch details below.

Echo: Decompress permits unbounded gzip expansion in v4

Also known asGHSA-h7wr-284f-5qvc

Published

Oct 28, 2026

Updated

Oct 29, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 29, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-118261.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs31th percentile — riskier than 31% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

🐹github.com/labstack/echo/v4

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

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.

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.

Fix commit.

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.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/labstack/echo/v4`	≥ 4.0.0&&< 4.16.1	4.16.1`go get github.com/labstack/echo/v4@v4.16.1`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/labstack/echo/v4, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/labstack/echo/v4 to 4.16.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-118261 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Frequently Asked Questions

## 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. ## Affected versions and patc

O3 Security · Impact-Aware SCA

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