# CVE-2021-47243: linux: In the Linux kernel, the following vulnerability has been resolved:  sch_cake: Fix out of bounds when parsing TCP opt...

CVE-2021-47243 is fixed in linux on 1 platform, first by DEBIAN-CVE-2021-47243, released May 21, 2024. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2021-47243
- Priority: High
- CVSS: 7.1 (high)
- EPSS: 0.0026
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: May 21, 2024

## Description

In the Linux kernel, the following vulnerability has been resolved:  sch_cake: Fix out of bounds when parsing TCP options and header  The TCP option parser in cake qdisc (cake_get_tcpopt and cake_tcph_may_drop) could read one byte out of bounds. When the length is 1, the execution flow gets into the loop, reads one byte of the opcode, and if the opcode is neither TCPOPT_EOL nor TCPOPT_NOP, it reads one more byte, which exceeds the length of 1.  This fix is inspired by commit 9609dad263f8 ("ipv4: tcp_input: fix stack out of bounds when parsing TCP options.").  v2 changes:  Added doff validation in cake_get_tcphdr to avoid parsing garbage as TCP header. Although it wasn't strictly an out-of-bounds access (memory was allocated), garbage values could be read where CAKE expected the TCP header if doff was smaller than 5.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 5.10.46-1 | [DEBIAN-CVE-2021-47243](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47243.md) | May 21, 2024 |
| Linux | linux Debian 13.5 (trixie) | 5.10.46-1 | [DEBIAN-CVE-2021-47243](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47243.md) | May 21, 2024 |
| Linux | linux Debian 14 | 5.10.46-1 | [DEBIAN-CVE-2021-47243](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47243.md) | May 21, 2024 |

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