An issue was discovered in shadow 4.5. newgidmap (in shadow-utils) is setuid and allows an unprivileged user to be placed in a user namespace where setgroups(2) is permitted. This allows an attacker to remove themselves from a supplementary group, which may allow access to certain filesystem paths if the administrator has used group blacklisting (e.g., chmod g-rwx) to restrict access to paths. This flaw effectively reverts a security feature in the kernel (in particular, the /proc/self/setgroups knob) to prevent this sort of privilege escalation.
The product specifies permissions for a security-critical resource in a way that allows that resource to be read or modified by unintended actors.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Shadow | Shadow_project | 4.5 (including) | 4.5 (including) |
| Shadow | Ubuntu | artful | * |
| Shadow | Ubuntu | bionic | * |
| Shadow | Ubuntu | cosmic | * |
| Shadow | Ubuntu | disco | * |
| Shadow | Ubuntu | eoan | * |
| Shadow | Ubuntu | esm-infra/xenial | * |
| Shadow | Ubuntu | precise/esm | * |
| Shadow | Ubuntu | trusty | * |
| Shadow | Ubuntu | trusty/esm | * |
| Shadow | Ubuntu | upstream | * |
| Shadow | Ubuntu | xenial | * |