systemd: Unsafe handling of hard links allowing privilege escalation
Published Jan 29, 2018
7.8
HIGHCVSS 3.1
EPSS 1.06%
Description
systemd-tmpfiles in systemd before 237 attempts to support ownership/permission changes on hardlinked files even if the fs.protected_hardlinks sysctl is turned off, which allows local users to bypass intended access restrictions via vectors involving a hard link to a file for which the user lacks write access, as demonstrated by changing the ownership of the /etc/passwd file.
Affected products
No data.
Configuration 1
- < 237
Configuration 2
- 8.0
No data.
Red Hat Enterprise Linux 7
systemd
Will not fix
| Product | Package | State | Advisory |
|---|---|---|---|
| Red Hat Enterprise Linux 7 | systemd | Will not fix | n/a |
No package ranges for this CVE.
Remediation
Red Hat statement
Red Hat Product Security has rated this issue as having Moderate security impact. This issue is not exploitable in the default configuration Red Hat Enterprise Linux. This issue is not currently planned to be addressed in future updates. For additional information, refer to the Issue Severity Classification: https://access.redhat.com/security/updates/classification/.
Red Hat mitigation
This flaw, and many others like it, is mitigated by enabling hardlink and symlink protections. These protections are enabled by default in Red Hat Enterprise Linux and this vulnerability will only be exploitable if disabled. To ensure your system is protected, check that `fs.protected_hardlinks` is enabled as in the following example: # sysctl fs.protected_hardlinks fs.protected_hardlinks = 1
References (13)
- http://lists.opensuse.org/opensuse-updates/2018-02/msg00109.html vendor-advisoryx_refsource_SUSEMailing ListThird Party Advisory
- http://packetstormsecurity.com/files/146184/systemd-Local-Privilege-Escalation.html x_refsource_MISCExploitThird Party AdvisoryVDB Entry
- http://www.openwall.com/lists/oss-security/2018/01/29/3 mailing-listx_refsource_MLISTExploitMailing ListThird Party Advisory
- https://access.redhat.com/security/cve/CVE-2017-18078 Vendor Advisory
- https://bugzilla.redhat.com/show_bug.cgi?id=1539758 Issue Tracking
- https://github.com/systemd/systemd/issues/7736 x_refsource_MISCExploitIssue TrackingThird Party Advisory
- https://lists.apache.org/thread.html/r58af02e294bd07f487e2c64ffc0a29b837db5600e33b6e698b9d696b%40%3Cissues.bookkeeper.apache.org%3E mailing-listx_refsource_MLIST
- https://lists.apache.org/thread.html/rf4c02775860db415b4955778a131c2795223f61cb8c6a450893651e4%40%3Cissues.bookkeeper.apache.org%3E mailing-listx_refsource_MLIST
- https://lists.debian.org/debian-lts-announce/2019/04/msg00022.html mailing-listx_refsource_MLISTMailing ListThird Party Advisory
- https://nvd.nist.gov/vuln/detail/CVE-2017-18078
- https://www.cve.org/CVERecord?id=CVE-2017-18078
- https://www.exploit-db.com/exploits/43935/ exploitx_refsource_EXPLOIT-DBThird Party AdvisoryVDB Entry
- https://www.openwall.com/lists/oss-security/2018/01/29/4 mailing-listx_refsource_MLISTMailing ListThird Party Advisory
Change history (0)
No recorded changes yet.