CVE-2026-55677 Echo: Encoded slash (%2F) bypasses route-level protection and exposes static files
Attackers can bypass route protections and read unauthorized static files by exploiting inconsistent URL decoding in the Echo Go web framework.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-55677?
CVE-2026-55677 is a high-severity path traversal vulnerability in labstack echo, published on 26 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Echo is a Go web framework. Prior to 4.15.3 and 5.2.0, Echo's router and static file handler disagree on URL path decoding. The router matches routes using the raw encoded path (preserving %2F as-is), while StaticDirectoryHandler unescapes %2F to / before resolving filesystem paths. This allows an attacker to bypass route-level access controls and read static files without authorization. This vulnerability is fixed in 4.15.3 and 5.2.0.
Weakness: CWE-22
Which versions are affected by CVE-2026-55677?
8 open source packages ship an affected version, including github.com/labstack/echo/v4, github.com/labstack/echo and github.com/labstack/echo/v5.
| Package | Affected | Fixed in |
|---|---|---|
github.com/labstack/echo/v4 Go | All versions | 4.15.3 |
github.com/labstack/echo/v4 Go | All versions | 4.15.3 |
github.com/labstack/echo/v4 Go | All versions | 4.15.3 |
github.com/labstack/echo Go | All versions to 3.3.10 | None |
github.com/labstack/echo Go | All versions to 3.3.10 | None |
github.com/labstack/echo/v5 Go | All versions | 5.2.0 |
2 more packages
github.com/labstack/echo/v5 Go | All versions | 5.2.0 |
github.com/labstack/echo/v5 Go | All versions | 5.2.0 |
How do I fix CVE-2026-55677?
Upgrade github.com/labstack/echo/v4 to 4.15.3 or later.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is CVE-2026-55677 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55677 exists.
Sources
Also known as CLEANSTART-2026-JO59032, CLEANSTART-2026-ON16702, CLEANSTART-2026-SS30538, CLSA-2026-1790266264, CLSA-2026-1790972556, DEBIAN-CVE-2026-55677 and 14 more.