CVE-2021-47243
sch_cake: Fix out of bounds when parsing TCP options and header
- Published
- Updated
- Reserved
- Assigned by
- Linux
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.
Timeline
ID reserved
By Linux
- 41 days later
· 41 days later
Published
- 2 years later
· 2 years later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| LinuxCNA (assigner) | 3.1 | High7.1 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H |
| NVDNVD · Modified | 3.1 | High7.1 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H |
- EPSS (exploitation in 30 days)
- 0.26% · top 82% of all CVEs (7 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.1.
Weakness
Affected products
- affected 8b7138814f29933898ecd31dfc83e35a30ee69f5 – < 595897ef118d6fe66690c4fc5b572028c9da95b7
- affected 8b7138814f29933898ecd31dfc83e35a30ee69f5 – < 4cefa061fc63f4d2dff5ab4083f43857cd7a2335
- affected 8b7138814f29933898ecd31dfc83e35a30ee69f5 – < 3b491dd593d582ceeb27aa617600712a6bd14246
- affected 8b7138814f29933898ecd31dfc83e35a30ee69f5 – < 3371392c60e2685af30bd4547badd880f5df2b3f
- affected 8b7138814f29933898ecd31dfc83e35a30ee69f5 – < ba91c49dedbde758ba0b72f57ac90b06ddf8e548
- affected 4.19
- unaffected < 4.19
- unaffected 4.19.196 – ≤ 4.19.*
- unaffected 5.4.128 – ≤ 5.4.*
- unaffected 5.10.46 – ≤ 5.10.*
- unaffected 5.12.13 – ≤ 5.12.*
- unaffected 5.13 – ≤ *
References (5)
- https://git.kernel.org/stable/c/595897ef118d6fe66690c4fc5b572028c9da95b7 (opens in a new tab)x_transferred
- https://git.kernel.org/stable/c/4cefa061fc63f4d2dff5ab4083f43857cd7a2335 (opens in a new tab)x_transferred
- https://git.kernel.org/stable/c/3b491dd593d582ceeb27aa617600712a6bd14246 (opens in a new tab)x_transferred
- https://git.kernel.org/stable/c/3371392c60e2685af30bd4547badd880f5df2b3f (opens in a new tab)x_transferred
- https://git.kernel.org/stable/c/ba91c49dedbde758ba0b72f57ac90b06ddf8e548 (opens in a new tab)x_transferred
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2021-47243)Record last updated .