CVE-2022-39957 [High] | Security Bypass in Owasp Modsecurity Core Rule Set

The OWASP ModSecurity Core Rule Set (CRS) is affected by a response body bypass. A client can issue an HTTP Accept header field containing an optional "charset" parameter in order to receive the response in an encoded form. Depending on the "charset", this response can not be decoded by the web application firewall. A restricted resource, access to which would ordinarily be detected, may therefore bypass detection. The legacy CRS versions 3.0.x and 3.1.x are affected, as well as the currently supported versions 3.2.1 and 3.3.2. Integrators and users are advised to upgrade to 3.2.2 and 3.3.3 respectively.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-05-24	0.29%	0.90%	+0.61%
2	2026-05-23	0.12%	0.29%	+0.17%
3	2025-11-21	—	0.12%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-05-24

0.29%

0.90%

+0.61%

2026-05-23

0.12%

0.29%

+0.17%

2025-11-21

—

0.12%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
7.3	3.1	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L` 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: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:L) Some sensitive info could get out, but not a total data dump. Integrity (I:L) Attackers could change some data, but it’s limited—not everything goes. Availability (A:L) Might cause slowdowns, glitches, or partial disruption—not a full brick.	3.9	3.4	[email protected]
7.5	3.1	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N` 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: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:N) Service keeps running; no real outage angle.	3.9	3.6	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

7.3

3.1

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L 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: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:L): Some sensitive info could get out, but not a total data dump.
Integrity (I:L): Attackers could change some data, but it’s limited—not everything goes.
Availability (A:L): Might cause slowdowns, glitches, or partial disruption—not a full brick.

3.9

3.4

[email protected]

7.5

3.1

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N 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: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:N): Service keeps running; no real outage angle.

3.9

3.6

[email protected]

OS Trackers for CVE-2022-39957

vendor	priority	summary	link
`debian`	not yet assigned	CVE-2022-39957 not yet assigned priority: Debian including 1 source packages (modsecurity-crs), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5.	https://security-tracker.debian.org/tracker/CVE-2022-39957
`gentoo`	low	CVE-2022-39957: 1 GLSA(s) (202305-25), 1 atom(s) (www-apache/modsecurity-crs); latest impact low.	https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2022-39957
`redhat`	medium	—	https://access.redhat.com/security/cve/CVE-2022-39957
`suse`	high	—	https://www.suse.com/security/cve/CVE-2022-39957/
`ubuntu`	low	CVE-2022-39957 low priority: Ubuntu including 1 source packages (modsecurity-crs), 13 status rows across 13 suites (bionic, focal, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): needs-triage 7, ignored 6.	https://ubuntu.com/security/CVE-2022-39957

Affected software / configurations for CVE-2022-39957

Vendor	Product	Version	Raw CPE
owasp	owasp_modsecurity_core_rule_set	>= 3.0.0, < 3.2.2	cpe:2.3:a:owasp:owasp_modsecurity_core_rule_set::::::::
owasp	owasp_modsecurity_core_rule_set	>= 3.3.0, < 3.3.3	cpe:2.3:a:owasp:owasp_modsecurity_core_rule_set::::::::
fedoraproject	fedora	35	cpe:2.3:o:fedoraproject:fedora:35:::::::*
fedoraproject	fedora	36	cpe:2.3:o:fedoraproject:fedora:36:::::::*
fedoraproject	fedora	37	cpe:2.3:o:fedoraproject:fedora:37:::::::*
debian	debian_linux	10.0	cpe:2.3:o:debian:debian_linux:10.0:::::::*

References for CVE-2022-39957

URL	Tags
https://coreruleset.org/20220919/crs-version-3-3-3-and-3-2-2-covering-several-cves/	Patch Vendor Advisory
https://lists.debian.org/debian-lts-announce/2023/01/msg00033.html	Mailing List Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/HL2L2GF7GOCWPMJZDUE5OXDSXHGG3XUJ/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/PD56EAYNGB6E6QQH62LAYCONOP6OH5DZ/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/YPQ6CCMX3MU4A7MTCGQJA7VMJW3IQDXV/
https://security.gentoo.org/glsa/202305-25
https://lists.debian.org/debian-lts-announce/2025/08/msg00004.html

URL

CVE-2022-39957 | Response body bypass in OWASP ModSecurity Core Rule Set via a specialy crafted charset in the HTTP Accept header

Exploit prediction scoring system (EPSS) score for CVE-2022-39957

Common vulnerability scoring system (CVSS) metrics for CVE-2022-39957

Weakness enumeration for CVE-2022-39957

OS Trackers for CVE-2022-39957

Affected software / configurations for CVE-2022-39957

References for CVE-2022-39957