CVE-2025-27556 [Medium] | Security Vulnerability in Django

An issue was discovered in Django 5.1 before 5.1.8 and 5.0 before 5.0.14. The NFKC normalization is slow on Windows. As a consequence, django.contrib.auth.views.LoginView, django.contrib.auth.views.LogoutView, and django.views.i18n.set_language are subject to a potential denial-of-service attack via certain inputs with a very large number of Unicode characters.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-06-15	0.01%	0.86%	+0.85%
2	2026-05-11	0.17%	0.01%	-0.16%
3	2026-01-27	—	0.17%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-06-15

0.01%

0.86%

+0.85%

2026-05-11

0.17%

0.01%

-0.16%

2026-01-27

—

0.17%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
5.8	3.1	MEDIUM	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/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:C) Breaking this can reach past the original component and bite other resources—bigger blast radius. Confidentiality (C:N) Doesn’t really leak secrets in a meaningful way. Integrity (I:N) Data isn’t meaningfully altered or forged. Availability (A:L) Might cause slowdowns, glitches, or partial disruption—not a full brick.	3.9	1.4	[email protected]
7.5	3.1	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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: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:N) Doesn’t really leak secrets in a meaningful 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.	3.9	3.6	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

5.8

3.1

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/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:C): Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:N): Doesn’t really leak secrets in a meaningful way.
Integrity (I:N): Data isn’t meaningfully altered or forged.
Availability (A:L): Might cause slowdowns, glitches, or partial disruption—not a full brick.

3.9

1.4

[email protected]

7.5

3.1

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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: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:N): Doesn’t really leak secrets in a meaningful 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.

3.9

3.6

[email protected]

OS Trackers for CVE-2025-27556

vendor	priority	summary	link
`debian`	unimportant	CVE-2025-27556 unimportant priority: Debian including 1 source packages (python-django), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5.	https://security-tracker.debian.org/tracker/CVE-2025-27556
`redhat`	medium	—	https://access.redhat.com/security/cve/CVE-2025-27556
`suse`	medium	CVE-2025-27556 severity moderate: SUSE including 7 source package names (python-Django, python311-Django, …), 9 product×package rows across 3 product lines (SUSE Linux Enterprise Module for Package Hub 15 SP6, openSUSE Leap 15.6, openSUSE Tumbleweed): Fixed 5, Known Not Affected 4.	https://www.suse.com/security/cve/CVE-2025-27556/
`ubuntu`	medium	CVE-2025-27556 medium priority: Ubuntu including 1 source packages (python-django), 8 status rows across 8 suites (bionic, focal, jammy, noble, oracular, trusty, upstream, xenial): not-affected 7, released 1.	https://ubuntu.com/security/CVE-2025-27556

Affected software / configurations for CVE-2025-27556

Vendor	Product	Version	Raw CPE
djangoproject	django	>= 5.0, < 5.0.14	cpe:2.3:a:djangoproject:django::::::::
djangoproject	django	>= 5.1, < 5.1.8	cpe:2.3:a:djangoproject:django::::::::

References for CVE-2025-27556

URL	Tags
https://docs.djangoproject.com/en/dev/releases/security/	Vendor Advisory
https://groups.google.com/g/django-announce	Vendor Advisory
https://www.djangoproject.com/weblog/2025/apr/02/security-releases/	Vendor Advisory
http://www.openwall.com/lists/oss-security/2025/04/02/2	Mailing List Third Party Advisory

URL

CVE-2025-27556

Exploit prediction scoring system (EPSS) score for CVE-2025-27556

Common vulnerability scoring system (CVSS) metrics for CVE-2025-27556

Weakness enumeration for CVE-2025-27556

GitHub Security Advisory for CVE-2025-27556

OS Trackers for CVE-2025-27556

Affected software / configurations for CVE-2025-27556

References for CVE-2025-27556