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CVE-2017-3737

Publication date 7 December 2017

Last updated 24 July 2024

Ubuntu priority

Medium

Why this priority?

Cvss 3 Severity Score

5.9 · Medium

Score breakdown

OpenSSL 1.0.2 (starting from version 1.0.2b) introduced an "error state" mechanism. The intent was that if a fatal error occurred during a handshake then OpenSSL would move into the error state and would immediately fail if you attempted to continue the handshake. This works as designed for the explicit handshake functions (SSL_do_handshake(), SSL_accept() and SSL_connect()), however due to a bug it does not work correctly if SSL_read() or SSL_write() is called directly. In that scenario, if the handshake fails then a fatal error will be returned in the initial function call. If SSL_read()/SSL_write() is subsequently called by the application for the same SSL object then it will succeed and the data is passed without being decrypted/encrypted directly from the SSL/TLS record layer. In order to exploit this issue an application bug would have to be present that resulted in a call to SSL_read()/SSL_write() being issued after having already received a fatal error. OpenSSL version 1.0.2b-1.0.2m are affected. Fixed in OpenSSL 1.0.2n. OpenSSL 1.1.0 is not affected.

Read the notes from the security team

Status

Package Ubuntu Release Status
openssl 17.10 artful
Fixed 1.0.2g-1ubuntu13.3
17.04 zesty
Fixed 1.0.2g-1ubuntu11.4
16.04 LTS xenial
Fixed 1.0.2g-1ubuntu4.10
14.04 LTS trusty
Not affected

Notes

leosilva

this issue does not affect OpenSSL 1.1.0

mdeslaur

1.0.2b introduced a security hardening mechanism designed to protect against bugs in application code. https://git.openssl.org/?p=openssl.git;a=commit;h=e4f77bf1833245d2b6aa4ce6a16c85e1cdf78589 This CVE applies to the hardening mechanism being incomplete. openssl versions older than 1.0.2b don't have the hardening mechanism at all.

Patch details

For informational purposes only. We recommend not to cherry-pick updates. How can I get the fixes?

Package Patch details
openssl

Severity score breakdown

Parameter Value
Base score 5.9 · Medium
Attack vector Network
Attack complexity High
Privileges required None
User interaction None
Scope Unchanged
Confidentiality High
Integrity impact None
Availability impact None
Vector CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

References

Related Ubuntu Security Notices (USN)

    • USN-3512-1
    • OpenSSL vulnerabilities
    • 11 December 2017

Other references