CVE-2018-15599 — The recv_msg_userauth_request function in svr-auth

The recv_msg_userauth_request function in svr-auth.c in Dropbear through 2018.76 is prone to a user enumeration vulnerability because username validity affects how fields in SSH_MSG_USERAUTH messages are handled, a similar issue to CVE-2018-15473 in an unrelated codebase.

01What is this vulnerability?

The recv_msg_userauth_request function in svr-auth.c in Dropbear through 2018.76 is prone to a user enumeration vulnerability because username validity affects how fields in SSH_MSG_USERAUTH messages are handled, a similar issue to CVE-2018-15473 in an unrelated codebase.

02Affected products

Vendor	Product	Versions
n	a / n/a	n/a

03Active exploitation status

Not currently listed on the CISA Known Exploited Vulnerabilities (KEV) catalog. EPSS is the best forward-looking signal — see the EPSS row above.

04Recommended remediation

• Patch to a fixed version listed in the vendor advisory (see references below).
• Mitigate with WAF rules, network egress filters, or feature flags where the patch is not yet available.
• Hunt historical logs for exploitation indicators — see Detection signatures below.

05Technical details

For the full vendor write-up, exploit chains, and reference implementations, see the references list in section 09.

06Detection signatures

Ask SARA in chat to draft a starting detection for this CVE in your stack of choice.

07Related CVEs

08Timeline

• Published: 2018-08-21T01:00:00.000Z
• Last modified: 2024-08-05T10:01:54.240Z

09References

• matt.ucc.asn.au — https://matt.ucc.asn.au/dropbear/CHANGES
• lists.ucc.gu.uwa.edu.au — http://lists.ucc.gu.uwa.edu.au/pipermail/dropbear/2018q3/002109.html
• lists.ucc.gu.uwa.edu.au — http://lists.ucc.gu.uwa.edu.au/pipermail/dropbear/2018q3/002108.html
• lists.debian.org — https://lists.debian.org/debian-lts-announce/2018/08/msg00026.html
• old.reddit.com — https://old.reddit.com/r/blackhat/comments/97ywnm/openssh_username_enumeration/e…