CVE-2019-15239

In the Linux kernel, a certain net/ipv4/tcp_output.c change, which was properly incorporated into 4.16.12, was incorrectly backported to the earlier longterm kernels, introducing a new vulnerability that was potentially more severe than the issue that was intended to be fixed by backporting. Specifically, by adding to a write queue between disconnection and re-connection, a local attacker can trigger multiple use-after-free conditions. This can result in a kernel crash, or potentially in privilege escalation. NOTE: this affects (for example) Linux distributions that use 4.9.x longterm kernels before 4.9.190 or 4.14.x longterm kernels before 4.14.139.

Weakness

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.

Affected Software

Potential Mitigations

References

• http://lists.opensuse.org/opensuse-security-announce/2019-09/msg00064.html
• http://lists.opensuse.org/opensuse-security-announce/2019-09/msg00066.html
• https://access.redhat.com/errata/RHSA-2019:3978
• https://access.redhat.com/errata/RHSA-2019:3979
• https://access.redhat.com/errata/RHSA-2020:0027
• https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7f582b248d0a86bae5788c548d7bb5bca6f7691a
• https://lore.kernel.org/stable/41a61a2f87691d2bc839f26cdfe6f5ff2f51e472.camel%40decadent.org.uk/
• https://pulsesecurity.co.nz/advisories/linux-kernel-4.9-tcpsocketsuaf
• https://salsa.debian.org/kernel-team/kernel-sec/blob/f6273af2d956a87296b6b60379d0a186c9be4bbc/active/CVE-2019-15239
• https://www.debian.org/security/2019/dsa-4497
• http://lists.opensuse.org/opensuse-security-announce/2019-09/msg00064.html
• http://lists.opensuse.org/opensuse-security-announce/2019-09/msg00066.html
• https://access.redhat.com/errata/RHSA-2019:3978
• https://access.redhat.com/errata/RHSA-2019:3979
• https://access.redhat.com/errata/RHSA-2020:0027
• https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7f582b248d0a86bae5788c548d7bb5bca6f7691a
• https://lore.kernel.org/stable/41a61a2f87691d2bc839f26cdfe6f5ff2f51e472.camel%40decadent.org.uk/
• https://pulsesecurity.co.nz/advisories/linux-kernel-4.9-tcpsocketsuaf
• https://salsa.debian.org/kernel-team/kernel-sec/blob/f6273af2d956a87296b6b60379d0a186c9be4bbc/active/CVE-2019-15239
• https://www.debian.org/security/2019/dsa-4497