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
Published · last modified .
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.
EPSS exploit prediction
EPSS: 0.787 (99.6th percentile), scored .
High probability of exploitation in the next 30 days — patch promptly. 100th percentile — 99.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.787 · newest: 0.787 · change: 0.000
Affected products
- OpenSSL — versions 1.0.2b, 1.0.2c, 1.0.2d
- OpenSSL Software Foundation — versions 1.0.2b-1.0.2m
- Debian Linux — versions 9.0
Weakness classification (CWE)
Public proof-of-concept exploits
References
- access.redhat.com/errata/RHSA-2018:2185 (vendor-advisory)
- access.redhat.com/errata/RHSA-2018:2186 (vendor-advisory)
- github.com/openssl/openssl/commit/898fb884b706aaeb283de4812340bb0bde8476dc
- www.oracle.com/technetwork/security-advisory/cpujul2018-4258247.html
- www.oracle.com/technetwork/security-advisory/cpujan2018-3236628.html
- security.netapp.com/advisory/ntap-20180419-0002/
- security.FreeBSD.org/advisories/FreeBSD-SA-17:12.openssl.asc (vendor-advisory, Third Party Advisory)
- security.gentoo.org/glsa/201712-03 (vendor-advisory, Third Party Advisory)
- www.securitytracker.com/id/1039978 (VDB Entry, Third Party Advisory, vdb-entry)
- www.openssl.org/news/secadv/20171207.txt (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.