CVE-2023-29409: Large RSA keys can cause high CPU usage in crypto/tls
Extremely large RSA keys in certificate chains can cause a client/server to expend significant CPU time verifying signatures. With fix, the size of RSA keys transmitted during handshakes is restricted to <= 8192 bits. Based on a survey of publicly trusted RSA keys, there are currently only three certificates in circulation with keys larger than this, and all three appear to be test certificates that are not actively deployed. It is possible there are larger keys in use in private PKIs, but we target the web PKI, so causing breakage here in the interests of increasing the default safety of users of crypto/tls seems reasonable.
Other sources
Golang Go is vulnerable to a denial of service, caused by an uncontrolled resource consumption flaw. By persuading a victim to use a specially crafted certificate with large RSA keys, an remote attacker could exploit this vulnerability to cause a client/server to expend significant CPU time verifying signatures, and results in a denial of service condition.
— IBM
Large RSA keys can cause high CPU usage in crypto/tls
— Microsoft
Affected Software
Remediation
Patch Available
Patch Available
Patch Available
Event History
Frequently Asked Questions
What is CVE-2023-29409?
CVE-2023-29409 refers to extremely large RSA keys in certificate chains that can cause a client/server to expend significant CPU time verifying signatures.
What is the severity of CVE-2023-29409?
The severity of CVE-2023-29409 is medium with a severity value of 5.3.
Which software is affected by CVE-2023-29409?
Software affected by CVE-2023-29409 include Golang Go versions up to 1.19.12, versions between 1.20.0 and 1.20.7, version 1.21.0-rc1, version 1.21.0-rc2, and version 1.21.0-rc3.
What is the fix for CVE-2023-29409?
The fix for CVE-2023-29409 restricts the size of RSA keys transmitted during handshakes to <= 8192 bits.
Are there any references for CVE-2023-29409?
Yes, there are references available for CVE-2023-29409. You can find them [here](https://go.dev/cl/515257), [here](https://groups.google.com/g/golang-announce/c/X0b6CsSAaYI/m/Efv5DbZ9AwAJ), and [here](https://pkg.go.dev/vuln/GO-2023-1987).