CVE-2026-5078 | morgan vulnerable to Log Forging via unneutralized control characters in :remote-user

Impact: The morgan logging middleware's :remote-user token extracts the Basic auth username from the Authorization request header and writes it to the log stream without neutralizing control characters. An unauthenticated attacker can send a crafted Authorization Basic header containing CR or LF bytes to inject forged log lines, breaking the one-request-per-line structure of access logs and enabling log forgery against downstream log consumers. The built-in combined, common, default, and short formats are affected, as well as any custom format that references :remote-user. Affected versions: morgan 1.2.0 through 1.10.1. Patches: upgrade to morgan 1.11.0, which neutralizes control characters in the :remote-user token output. Workarounds: use a custom format string that does not include :remote-user.

Published: 2026-06-03 Last update: 2026-06-04 Assigner: ce714d77-add3-4f53-aff5-83d477b104bb Source: ce714d77-add3-4f53-aff5-83d477b104bb
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-5078 is rated Low Risk (26.8/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.24%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

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-2026-5078

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 0.05% 0.24% +0.19%
2 2026-06-09 0.03% 0.05% +0.02%
3 2026-06-03 — 0.03% —

Full EPSS history (3 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-5078

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.3 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/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:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 1.4 ce714d77-add3-4f53-aff5-83d477b104bb

Weakness enumeration for CVE-2026-5078

OS Trackers for CVE-2026-5078

vendor priority summary link
ubuntu medium CVE-2026-5078 medium priority: Ubuntu including 1 source packages (node-morgan), 5 status rows across 5 suites (jammy, noble, questing, resolute, upstream): needs-triage 5. https://ubuntu.com/security/CVE-2026-5078

Affected software / configurations for CVE-2026-5078

Vendor Product Version Raw CPE
morgan_project morgan >= 1.2.0, < 1.11.0 cpe:2.3:a:morgan_project:morgan:*:*:*:*:*:node.js:*:*

References for CVE-2026-5078

cvelogic Threat Intelligence