Fedora Account System
Red Hat Associate
Red Hat Customer
In Shadow 4.13, it is possible to inject control characters into fields provided to the SUID program chfn (change finger). Although it is not possible to exploit this directly (e.g., adding a new user fails because \n is in the block list), it is possible to misrepresent the /etc/passwd file when viewed. Use of \r manipulations and Unicode characters to work around blocking of the : character make it possible to give the impression that a new user has been added. In other words, an adversary may be able to convince a system administrator to take the system offline (an indirect, social-engineered denial of service) by demonstrating that "cat /etc/passwd" shows a rogue user account. https://github.com/shadow-maint/shadow/commit/e5905c4b84d4fb90aefcd96ee618411ebfac663d https://www.trustwave.com/en-us/resources/security-resources/security-advisories/?fid=31797 https://github.com/shadow-maint/shadow/pull/687 https://www.trustwave.com/en-us/resources/blogs/spiderlabs-blog/cve-2023-29383-abusing-linux-chfn-to-misrepresent-etc-passwd/
Created shadow-utils tracking bugs for this issue: Affects: fedora-all [bug 2187190]
chfn is provided in Fedora and RHEL by util-linux package, and not by shadow-utils. Thus, should I change the ownership of the bugzillas, or should I close them? It isn't clear to me as I know there is another bugzilla but it is embargoed and I can't see its content.
Created util-linux tracking bugs for this issue: Affects: fedora-all [bug 2187215]
Did you read the original blog post about this issue? https://www.trustwave.com/en-us/resources/blogs/spiderlabs-blog/cve-2023-29383-abusing-linux-chfn-to-misrepresent-etc-passwd/ There is a note about util-linux: Remember at the start where I said chfn can be found in util-linux and shadow packages? Well strangely enough, the util-linux version blocks control characters via “iscntrl” in ch-common.c. In addition, it adds the “ character into the blacklist, so perhaps there is a story and some research behind that one too? IMHO, we can close this CVE for RHEL and Fedora.
Ping .. see comment #7.
This bug is now closed. Further updates for individual products will be reflected on the CVE page(s): https://access.redhat.com/security/cve/cve-2023-29383