Out-of-bounds Read in OpenSSL
CVE-2017-3737
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.
Vulnerability class: Buffer Overflow
EPSS: 0.787 (99.6th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 5.9 (Medium). Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N.
Affected products
- Openssl — versions 1.0.2b, 1.0.2c, 1.0.2d
- Openssl Software Foundation — versions 1.0.2b-1.0.2m
- Debian Debian_linux — versions 9.0
Weakness classification (CWE)
Public proof-of-concept exploits
References
- openssl-security@openssl.org (x_refsource_REDHAT, vendor-advisory)
- openssl-security@openssl.org (x_refsource_REDHAT, vendor-advisory)
- openssl-security@openssl.org (x_refsource_CONFIRM)
- openssl-security@openssl.org (x_refsource_CONFIRM)
- openssl-security@openssl.org (x_refsource_CONFIRM)
- openssl-security@openssl.org (x_refsource_CONFIRM)
- openssl-security@openssl.org (x_refsource_FREEBSD, vendor-advisory, Third Party Advisory)
- openssl-security@openssl.org (vendor-advisory, Third Party Advisory, x_refsource_GENTOO)
- openssl-security@openssl.org (VDB Entry, Third Party Advisory, vdb-entry, x_refsource_SECTRACK)
- openssl-security@openssl.org (x_refsource_CONFIRM, Vendor Advisory)
Frequently asked questions
- What is CVE-2017-3737?
- CVE-2017-3737 is a medium-severity vulnerability in OpenSSL, classified under Out-of-bounds Read. CVSS score: 5.9/10. Published 2017-12-07.
- How severe is CVE-2017-3737?
- Medium severity. CVSS v3 base score is 5.9 out of 10.
- Is CVE-2017-3737 known to be exploited?
- 5 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.