CVE-2017-5551 — The simple_set_acl function in fs/posix_acl

The simple_set_acl function in fs/posix_acl.c in the Linux kernel before 4.9.6 preserves the setgid bit during a setxattr call involving a tmpfs filesystem, which allows local users to gain group privileges by leveraging the existence of a setgid program with restrictions on exec

01What is this vulnerability?

The simple_set_acl function in fs/posix_acl.c in the Linux kernel before 4.9.6 preserves the setgid bit during a setxattr call involving a tmpfs filesystem, which allows local users to gain group privileges by leveraging the existence of a setgid program with restrictions on execute permissions. NOTE: this vulnerability exists because of an incomplete fix for CVE-2016-7097.

02Affected products

No structured affected-product list available — see references below for vendor advisories.

03Active exploitation status

Not currently listed on the CISA Known Exploited Vulnerabilities (KEV) catalog. EPSS is the best forward-looking signal — see the EPSS row above.

04Recommended remediation

• Patch to a fixed version listed in the vendor advisory (see references below).
• Mitigate with WAF rules, network egress filters, or feature flags where the patch is not yet available.
• Hunt historical logs for exploitation indicators — see Detection signatures below.

05Technical details

For the full vendor write-up, exploit chains, and reference implementations, see the references list in section 09.

06Detection signatures

Ask SARA in chat to draft a starting detection for this CVE in your stack of choice.

07Related CVEs

08Timeline

• Published: 2017-02-06T06:59:00.717
• Last modified: 2026-05-13T00:24:29.033

09References

• git.kernel.org — http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=497de0…
• www.debian.org — http://www.debian.org/security/2017/dsa-3791
• www.kernel.org — http://www.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.9.6
• www.openwall.com — http://www.openwall.com/lists/oss-security/2017/01/21/3
• www.securityfocus.com — http://www.securityfocus.com/bid/95717
• www.securitytracker.com — http://www.securitytracker.com/id/1038053
• bugzilla.redhat.com — https://bugzilla.redhat.com/show_bug.cgi?id=1416126
• github.com — https://github.com/torvalds/linux/commit/497de07d89c1410d76a15bec2bb41f24a2a89f3…
• git.kernel.org — http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=497de0…
• www.debian.org — http://www.debian.org/security/2017/dsa-3791