CVE-2026-3902 | ASGI header spoofing via underscore/hyphen conflation

An issue was discovered in 6.0 before 6.0.4, 5.2 before 5.2.13, and 4.2 before 4.2.30. `ASGIRequest` allows a remote attacker to spoof headers by exploiting an ambiguous mapping of two header variants (with hyphens or with underscores) to a single version with underscores. Earlier, unsupported Django series (such as 5.0.x, 4.1.x, and 3.2.x) were not evaluated and may also be affected. Django would like to thank Tarek Nakkouch for reporting this issue.

Published: 2026-04-07 Last update: 2026-04-13 Assigner: 6a34fbeb-21d4-45e7-8e0a-62b95bc12c92 Source: 6a34fbeb-21d4-45e7-8e0a-62b95bc12c92

Conclusion & alert: CVE-2026-3902 is rated Moderate Risk (42.5/100): CVSS High severity, with low exploitation likelihood (EPSS 0.44%). Mandatory action: Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-3902

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.04% 0.44% +0.40%
2 2026-04-08 0.04%

Full EPSS history (2 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-3902

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/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:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
3.9 3.6 134c704f-9b21-4f2e-91b3-4a467353bcc0

Weakness enumeration for CVE-2026-3902

GitHub Security Advisory for CVE-2026-3902

GHSA-mvfq-ggxm-9mc5 · Severity: high · Ecosystem: pip — Django vulnerable to ASGI header spoofing via underscore/hyphen conflation

OS Trackers for CVE-2026-3902

vendor priority summary link
alpine CVE-2026-3902: 1 source package rows (py3-django); 2 state rows across 2 repos (3.23-community, edge-community); fixed 2, open 0. https://security.alpinelinux.org/vuln/CVE-2026-3902
debian not yet assigned CVE-2026-3902 not yet assigned priority: Debian including 1 source packages (python-django), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): open 3, resolved 2. https://security-tracker.debian.org/tracker/CVE-2026-3902
redhat medium https://access.redhat.com/security/cve/CVE-2026-3902
suse medium CVE-2026-3902 severity moderate: SUSE including 5 source package names (python311-Django4-4.2.30-1.1, python313-Django4-4.2.30-1.1, python313-Django6-6.0.4-1.1, python314-Django4-4.2.30-1.1, python314-Django6-6.0.4-1.1), 5 product×package rows across 1 product lines (openSUSE Tumbleweed): Fixed 5. https://www.suse.com/security/cve/CVE-2026-3902/
ubuntu low CVE-2026-3902 low priority: Ubuntu including 1 source packages (python-django), 8 status rows across 8 suites (bionic, focal, jammy, noble, questing, trusty, upstream, xenial): not-affected 4, released 4. https://ubuntu.com/security/CVE-2026-3902

Affected software / configurations for CVE-2026-3902

Vendor Product Version Raw CPE
djangoproject django >= 4.2, < 4.2.30 cpe:2.3:a:djangoproject:django:*:*:*:*:*:*:*:*
djangoproject django >= 5.2, < 5.2.13 cpe:2.3:a:djangoproject:django:*:*:*:*:*:*:*:*
djangoproject django >= 6.0, < 6.0.4 cpe:2.3:a:djangoproject:django:*:*:*:*:*:*:*:*

References for CVE-2026-3902

cvelogic Threat Intelligence