CVE-2019-18634

NameCVE-2019-18634
DescriptionIn Sudo before 1.8.26, if pwfeedback is enabled in /etc/sudoers, users can trigger a stack-based buffer overflow in the privileged sudo process. (pwfeedback is a default setting in Linux Mint and elementary OS; however, it is NOT the default for upstream and many other packages, and would exist only if enabled by an administrator.) The attacker needs to deliver a long string to the stdin of getln() in tgetpass.c.
SourceCVE (at NVD; CERT, LWN, oss-sec, fulldisc, bugtraq, EDB, Metasploit, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, Mageia, GitHub code/issues, web search, more)
ReferencesDLA-2094-1, DSA-4614-1
NVD severitymedium
Debian Bugs950371

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
sudo (PTS)jessie1.8.10p3-1+deb8u5vulnerable
jessie (security)1.8.10p3-1+deb8u7fixed
stretch (security), stretch1.8.19p1-2.1+deb9u2fixed
buster1.8.27-1+deb10u2fixed
buster (security)1.8.27-1+deb10u1vulnerable
bullseye, sid1.9.0-1fixed

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
sudosource(unstable)1.8.31-1950371
sudosourcebuster1.8.27-1+deb10u2
sudosourcejessie1.8.10p3-1+deb8u7DLA-2094-1
sudosourcestretch1.8.19p1-2.1+deb9u2DSA-4614-1

Notes

https://www.sudo.ws/alerts/pwfeedback.html
https://www.openwall.com/lists/oss-security/2020/01/30/6
https://github.com/sudo-project/sudo/commit/fa8ffeb17523494f0e8bb49a25e53635f4509078 (master)
https://github.com/sudo-project/sudo/commit/b5d2010b6514ff45693509273bb07df3abb0bf0a (SUDO_1_8_31)
The issue itself is fixed only in 1.8.31 but a change in the EOF handling
introduced in 1.8.26 mitigated exploitation of the bug in some cases:
https://www.openwall.com/lists/oss-security/2020/01/31/1
Change for "Print a warning for password read issues" in 1.8.26:
https://github.com/sudo-project/sudo/commit/ab2cba0f5d8b286e8e52c06076efd32434f538ae (SUDO_1_8_26)
The overflow is tough as well reachable when using a pty:
https://www.openwall.com/lists/oss-security/2020/02/05/2

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