CVE-2020-36791 [High] | Out-of-bounds Read in Linux Kernel

In the Linux kernel, the following vulnerability has been resolved: net_sched: keep alloc_hash updated after hash allocation In commit 599be01ee567 ("net_sched: fix an OOB access in cls_tcindex") I moved cp->hash calculation before the first tcindex_alloc_perfect_hash(), but cp->alloc_hash is left untouched. This difference could lead to another out of bound access. cp->alloc_hash should always be the size allocated, we should update it after this tcindex_alloc_perfect_hash().

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-06-15	0.06%	0.15%	+0.09%
2	2026-03-03	0.01%	0.06%	+0.05%
3	2025-11-11	—	0.01%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-06-15

0.06%

0.15%

+0.09%

2026-03-03

0.01%

0.06%

+0.05%

2025-11-11

—

0.01%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
7.1	3.1	HIGH	`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H` Click to expand Attack vector (AV:L) They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:L) A normal user session is enough; they don’t have to be admin. User interaction (UI:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:H) Serious risk that confidential data gets exposed in a big way. Integrity (I:N) Data isn’t meaningfully altered or forged. Availability (A:H) Could take the service down hard or make it unusable for people who depend on it.	1.8	5.2	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

7.1

3.1

HIGH

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H Click to expand

Attack vector (AV:L): They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L): Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L): A normal user session is enough; they don’t have to be admin.
User interaction (UI:N): Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U): Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H): Serious risk that confidential data gets exposed in a big way.
Integrity (I:N): Data isn’t meaningfully altered or forged.
Availability (A:H): Could take the service down hard or make it unusable for people who depend on it.

1.8

5.2

[email protected]

OS Trackers for CVE-2020-36791

vendor	priority	summary	link
`debian`	not yet assigned	CVE-2020-36791 not yet assigned priority: Debian including 1 source packages (linux), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5.	https://security-tracker.debian.org/tracker/CVE-2020-36791
`redhat`	medium	—	https://access.redhat.com/security/cve/CVE-2020-36791
`suse`	medium	—	https://www.suse.com/security/cve/CVE-2020-36791/
`ubuntu`	medium	CVE-2020-36791 medium priority: Ubuntu including 144 source packages (linux, linux-allwinner-5.19, …), 1285 status rows across 9 suites (bionic, focal, jammy, noble, oracular, plucky, trusty, upstream, xenial): DNE 921, ignored 146, not-affected 123, released 95.	https://ubuntu.com/security/CVE-2020-36791

Affected software / configurations for CVE-2020-36791

Vendor	Product	Version	Raw CPE
linux	linux_kernel	>= 4.4.214, < 4.4.218	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 4.9.214, < 4.9.218	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 4.14.171, < 4.14.175	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 4.19.103, < 4.19.114	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 5.4.19, < 5.4.29	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 5.5.3, < 5.5.14	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	5.6	cpe:2.3:o:linux:linux_kernel:5.6:rc1::::::
linux	linux_kernel	5.6	cpe:2.3:o:linux:linux_kernel:5.6:rc2::::::
linux	linux_kernel	5.6	cpe:2.3:o:linux:linux_kernel:5.6:rc3::::::
linux	linux_kernel	5.6	cpe:2.3:o:linux:linux_kernel:5.6:rc4::::::
linux	linux_kernel	5.6	cpe:2.3:o:linux:linux_kernel:5.6:rc5::::::
linux	linux_kernel	5.6	cpe:2.3:o:linux:linux_kernel:5.6:rc6::::::
linux	linux_kernel	5.6	cpe:2.3:o:linux:linux_kernel:5.6:rc7::::::

References for CVE-2020-36791

URL	Tags
https://blog.cdthoughts.ch/2021/03/16/syzbot-bug.html	Third Party Advisory
https://git.kernel.org/stable/c/0d1c3530e1bd38382edef72591b78e877e0edcd3	Patch
https://git.kernel.org/stable/c/557d015ffb27b672e24e6ad141fd887783871dc2	Patch
https://git.kernel.org/stable/c/9f8b6c44be178c2498a00b270872a6e30e7c8266	Patch
https://git.kernel.org/stable/c/bd3ee8fb6371b45c71c9345cc359b94da2ddefa9	Patch
https://git.kernel.org/stable/c/c4453d2833671e3a9f6bd52f0f581056c3736386	Patch
https://git.kernel.org/stable/c/d23faf32e577922b6da20bf3740625c1105381bf	Patch
https://git.kernel.org/stable/c/d6cdc5bb19b595486fb2e6661e5138d73a57f454	Patch
https://syzkaller.appspot.com/bug?id=ea260693da894e7b078d18fca2c9c0a19b457534	Issue Tracking

URL

CVE-2020-36791 | net_sched: keep alloc_hash updated after hash allocation

Exploit prediction scoring system (EPSS) score for CVE-2020-36791

Common vulnerability scoring system (CVSS) metrics for CVE-2020-36791

Weakness enumeration for CVE-2020-36791

OS Trackers for CVE-2020-36791

Affected software / configurations for CVE-2020-36791

References for CVE-2020-36791