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CVE-2025-31135

MEDIUMCVSS 5.3/10EPSS 0.33%

Last modified

CVE-2025-31135 is a medium-severity vulnerability rated 5.3/10 on the CVSS scale. Go-Guerrilla SMTP Daemon is a lightweight SMTP server written in Go. Prior to 1.6.7, when ProxyOn is enabled, the PROXY command will be accepted multiple times, with later invocations overriding earlier ones. EPSS estimates a 0.33% chance of exploitation in the next 30 days.

Description

Go-Guerrilla SMTP Daemon is a lightweight SMTP server written in Go. Prior to 1.6.7, when ProxyOn is enabled, the PROXY command will be accepted multiple times, with later invocations overriding earlier ones. The proxy protocol only supports one initial PROXY header; anything after that is considered part of the exchange between client and server, so the client is free to send further PROXY commands with whatever data it pleases. go-guerrilla will treat these as coming from the reverse proxy, allowing a client to spoof its IP address. This vulnerability is fixed in 1.6.7.

Metrics

CVSS 3.1
5.3/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

EPSS Probability
0.33%

24.9th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

References

Timeline

Published
Last Modified
Status
Deferred

Frequently Asked Questions

What is CVE-2025-31135?
Go-Guerrilla SMTP Daemon is a lightweight SMTP server written in Go. Prior to 1.6.7, when ProxyOn is enabled, the PROXY command will be accepted multiple times, with later invocations overriding earlier ones. The proxy protocol only supports one initial PROXY header; anything after that is considered part of the exchange between client and server, so the client is free to send further PROXY commands with whatever data it pleases. go-guerrilla will treat these as coming from the reverse proxy, allowing a client to spoof its IP address. This vulnerability is fixed in 1.6.7.
How severe is CVE-2025-31135?
CVE-2025-31135 has a CVSS score of 5.3/10 (MEDIUM severity). The EPSS model estimates a 0.33% probability of exploitation in the next 30 days.
How do I fix CVE-2025-31135?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2025-31135?

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Source: NVD / NIST