CVE-2023-4039

Published: 12 September 2023

**DISPUTED**A failure in the -fstack-protector feature in GCC-based toolchains that target AArch64 allows an attacker to exploit an existing buffer overflow in dynamically-sized local variables in your application without this being detected. This stack-protector failure only applies to C99-style dynamically-sized local variables or those created using alloca(). The stack-protector operates as intended for statically-sized local variables. The default behavior when the stack-protector detects an overflow is to terminate your application, resulting in controlled loss of availability. An attacker who can exploit a buffer overflow without triggering the stack-protector might be able to change program flow control to cause an uncontrolled loss of availability or to go further and affect confidentiality or integrity. NOTE: The GCC project argues that this is a missed hardening bug and not a vulnerability by itself.

Notes

gcc-3.3 only provides libstdc++5

patches are expected to be provided for upstream versions 11, 12,
13 and trunk
Any possible package on arm64 in Ubuntu could be affected by this
and would therefore need to be recompiled by a new version of gcc containing
this fix - however, performing a whole-of-archive rebuild is not feasible. It
might be possible to detect which packages need to be rebuilt by looking for
those with the -fstack-clash-protection mitigation via hardening-check (as
since Ubuntu 20.04 LTS nearly all packages are compiled with this by
default). This is still likely to be quite a large subset of the archive and
still not feasible to rebuild. Instead as regular security / SRU updates are
performed for packages, they will opportunistically receive this fix.

14.04 LTS (trusty) Pro Infra and 16.04 LTS (xenial) Pro Infra
do not support Arm64 as an architecture.

Status

Severity score breakdown

References

• https://developer.arm.com/Arm%20Security%20Center/GCC%20Stack%20Protector%20Vulnerability%20AArch64
• https://github.com/metaredteam/external-disclosures/security/advisories/GHSA-x7ch-h5rf-w2mf
• https://rtx.meta.security/mitigation/2023/09/12/CVE-2023-4039.html
• https://www.cve.org/CVERecord?id=CVE-2023-4039
• NVD
• Launchpad
• Debian