Server-Side Request Forgery (SSRF) protection in the UrlImageConverter component of Apache Fesod…

Why it is Amber

• CVSS 9.1 critical
• Remotely exploitable without logging in

References

• https://cve.org/CVERecord?id=CVE-2026-49328
• https://github.com/apache/fesod/pull/1035
• https://github.com/apache/fesod/releases/tag/2.1.0-incubating
• https://lists.apache.org/thread/oh706yhm32hmw8vx4kh1948h952pfr83

Original description

Server-Side Request Forgery (SSRF) protection in the UrlImageConverter component of Apache Fesod (Incubating) fesod-sheet 2.0.2-incubating can be bypassed through DNS rebinding. When an application accepts an attacker-controlled image URL for spreadsheet writing, the converter checks the hostname's resolved IP addresses and then opens a separate connection that can resolve the hostname again. An attacker who controls DNS responses for the URL hostname may cause the connection to reach a restricted address after validation. CVE-2026-49328 covers SSRF in releases before 2.0.2-incubating; this issue is a DNS rebinding bypass of the protection in 2.0.2-incubating. Apache Fesod (Incubating) 2.1.0-incubating addresses the reported default-fetch scenario by disabling remote URL image fetching by default and requiring an explicit exact-host allowlist when the feature is enabled. Users should upgrade to 2.1.0-incubating. Applications enabling remote URL image fetching should allowlist only hostnames whose DNS and HTTP services are trusted.