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osvGoogleOSV:GO-2023-1987
HistoryAug 02, 2023 - 5:25 p.m.

Large RSA keys can cause high CPU usage in crypto/tls

2023-08-0217:25:58
Google
osv.dev
12
rsa keys
cpu usage
certificate chains
security
crypto/tls
handshakes
key size
web pki
public keys

CVSS3

5.3

Attack Vector

NETWORK

Attack Complexity

LOW

Privileges Required

NONE

User Interaction

NONE

Scope

UNCHANGED

Confidentiality Impact

NONE

Integrity Impact

NONE

Availability Impact

LOW

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

AI Score

7.1

Confidence

High

EPSS

0.001

Percentile

31.3%

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.

CVSS3

5.3

Attack Vector

NETWORK

Attack Complexity

LOW

Privileges Required

NONE

User Interaction

NONE

Scope

UNCHANGED

Confidentiality Impact

NONE

Integrity Impact

NONE

Availability Impact

LOW

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

AI Score

7.1

Confidence

High

EPSS

0.001

Percentile

31.3%