Machine-written summary
Summary written by Claude Haiku from the source advisory. Not reviewed by a person.
The chi middleware package github.com/go-chi/chi/v5/middleware, versions 5.2.1 up to but not including 5.3.0, has an IP spoofing flaw in RealIP, which takes the leftmost X-Forwarded-For value as the client address without checking trusted proxies. A remote attacker can send a forged header to bypass IP-based access controls and rate limits, or to write false addresses into logs. Upgrade to version 5.3.0 or later. The source gives no other workaround beyond stopping use of RealIP where request headers are not sanitized by a trusted proxy.
Not analysed yet
We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.
Severity and exploitation
| Score | Rating | CVSS | Vector | Source |
|---|---|---|---|---|
| 6.9 | Medium | 4.0 | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N | CNA (VulnCheck) |
- CISA KEV Not listed.
- EPSS 0.0050, the 42nd percentile, on 10 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.
Timeline
- 25 Jun 2026, 18:21 UTC Confirmed by GitHub Advisory Database
- 31 Oct 2026, 14:14 UTC First seen by agentprime
- 31 Oct 2026, 14:14 UTC Confirmed by OSV