CVE-2023-4091

Name	CVE-2023-4091
Description	A vulnerability was discovered in Samba, where the flaw allows SMB clients to truncate files, even with read-only permissions when the Samba VFS module "acl_xattr" is configured with "acl_xattr:ignore system acls = yes". The SMB protocol allows opening files when the client requests read-only access but then implicitly truncates the opened file to 0 bytes if the client specifies a separate OVERWRITE create disposition request. The issue arises in configurations that bypass kernel file system permissions checks, relying solely on Samba's permissions.
Source	CVE (at NVD; CERT, LWN, oss-sec, fulldisc, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)
References	DLA-3792-1, DSA-5525-1, DSA-5647-1

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
samba (PTS)	buster	2:4.9.5+dfsg-5+deb10u3	vulnerable
	buster (security)	2:4.9.5+dfsg-5+deb10u5	fixed
	bullseye	2:4.13.13+dfsg-1~deb11u5	vulnerable
	bullseye (security)	2:4.13.13+dfsg-1~deb11u6	fixed
	bookworm, bookworm (security)	2:4.17.12+dfsg-0+deb12u1	fixed
	trixie	2:4.19.5+dfsg-1	fixed
	sid	2:4.19.6+dfsg-1	fixed

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

Package	Type	Release	Fixed Version	Origin
samba	source	buster	2:4.9.5+dfsg-5+deb10u5	DLA-3792-1
samba	source	bullseye	2:4.13.13+dfsg-1~deb11u6	DSA-5647-1
samba	source	bookworm	2:4.17.12+dfsg-0+deb12u1	DSA-5525-1
samba	source	(unstable)	2:4.19.1+dfsg-1

Notes

https://www.samba.org/samba/security/CVE-2023-4091.html
In scope for continued Samba support
Fixed by: https://git.samba.org/?p=samba.git;a=commit;h=b08a60160e6ab8d982d31844bcbf7ab67ff3a8de (samba-4.17.12)
Fixed by: https://git.samba.org/?p=samba.git;a=commit;h=8b26f634372f11edcbea33dfd68a3d57889dfcc5 (samba-4.17.12)