CVE-2021-33657 [High] | Out-of-bounds Write in Simple Directmedia Layer

There is a heap overflow problem in video/SDL_pixels.c in SDL (Simple DirectMedia Layer) 2.x to 2.0.18 versions. By crafting a malicious .BMP file, an attacker can cause the application using this library to crash, denial of service or Code execution.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-05-05	0.10%	0.26%	+0.16%
2	2025-11-21	1.06%	0.10%	-0.97%
3	2025-11-18	—	1.06%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-05-05

0.10%

0.26%

+0.16%

2025-11-21

1.06%

0.10%

-0.97%

2025-11-18

—

1.06%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
8.8	3.1	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H` Click to expand Attack vector (AV:N) Could be attacked over the internet or any normal routed network—not just someone sitting at the machine. 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:N) No account or special rights needed—anonymous or random user is enough. User interaction (UI:R) A real person has to do something—click, install, enable—otherwise it doesn’t land. 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:H) They could widely tamper with or forge data—trust in the data is badly hurt. Availability (A:H) Could take the service down hard or make it unusable for people who depend on it.	2.8	5.9	[email protected]
6.8	2.0	MEDIUM	`AV:N/AC:M/Au:N/C:P/I:P/A:P` Click to expand Access vector (AV:N) Can be exploited remotely over network reachability. Access complexity (AC:M) Exploitation needs some favorable conditions, but not exceptional ones. Authentication (AU:N) No authentication is required. Confidentiality impact (C:P) Partial confidentiality impact. Integrity impact (I:P) Partial integrity impact. Availability impact (A:P) Partial availability impact.	8.6	6.4	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

8.8

3.1

HIGH

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

Attack vector (AV:N): Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
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:N): No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R): A real person has to do something—click, install, enable—otherwise it doesn’t land.
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:H): They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H): Could take the service down hard or make it unusable for people who depend on it.

2.8

5.9

[email protected]

6.8

2.0

MEDIUM

AV:N/AC:M/Au:N/C:P/I:P/A:P Click to expand

Access vector (AV:N): Can be exploited remotely over network reachability.
Access complexity (AC:M): Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N): No authentication is required.
Confidentiality impact (C:P): Partial confidentiality impact.
Integrity impact (I:P): Partial integrity impact.
Availability impact (A:P): Partial availability impact.

8.6

6.4

[email protected]

OS Trackers for CVE-2021-33657

vendor	priority	summary	link
`alpine`	high	CVE-2021-33657: 1 source package rows (sdl2); 7 state rows across 7 repos (3.17-community, 3.18-community, 3.19-community, 3.20-community, 3.21-community, 3.22-community, edge-community); fixed 7, open 0.	https://security.alpinelinux.org/vuln/CVE-2021-33657
`debian`	not yet assigned	CVE-2021-33657 not yet assigned priority: Debian including 2 source packages (libsdl1.2, libsdl2), 7 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 6, open 1.	https://security-tracker.debian.org/tracker/CVE-2021-33657
`gentoo`	normal	CVE-2021-33657: 2 GLSA(s) (202305-17, 202305-18), 2 atom(s) (media-libs/libsdl, media-libs/libsdl2); latest impact normal.	https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2021-33657
`suse`	high	CVE-2021-33657 severity important: SUSE including 29 source package names (SDL-1.2.13-106.21.1, SDL-1.2.15-1.1, …), 186 product×package rows across 58 product lines (HPE Helion OpenStack 8, SUSE CaaS Platform 4.0, … (58 product lines)): Fixed 186.	https://www.suse.com/security/cve/CVE-2021-33657/
`ubuntu`	medium	CVE-2021-33657 medium priority: Ubuntu including 2 source packages (libsdl1.2, libsdl2), 28 status rows across 14 suites (bionic, focal, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): not-affected 8, needed 6, DNE 5, released 5, ignored 3, needs-triage 1.	https://ubuntu.com/security/CVE-2021-33657

Affected software / configurations for CVE-2021-33657

Vendor	Product	Version	Raw CPE
libsdl	simple_directmedia_layer	>= 2.0.0, <= 2.0.18	cpe:2.3:a:libsdl:simple_directmedia_layer::::::::

References for CVE-2021-33657

URL	Tags
https://github.com/libsdl-org/SDL/commit/8c91cf7dba5193f5ce12d06db1336515851c9ee9	Patch Third Party Advisory
https://lists.debian.org/debian-lts-announce/2023/02/msg00008.html
https://security.gentoo.org/glsa/202305-17
https://security.gentoo.org/glsa/202305-18

URL

CVE-2021-33657

Exploit prediction scoring system (EPSS) score for CVE-2021-33657

Common vulnerability scoring system (CVSS) metrics for CVE-2021-33657

Weakness enumeration for CVE-2021-33657

OS Trackers for CVE-2021-33657

Affected software / configurations for CVE-2021-33657

References for CVE-2021-33657