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CVE-2026-103321

HIGH 8.3

Published 2026-09-30 · Last modified 2026-09-30

MISP contains a stored cross-site script (XSS) vulnerability in the event graph preview feature. The event graph preview image field was accepted and stored without server-side validation. On the client side, the stored value was rendered into an HTML img element's src attribute via string concatenation, allowing a crafted value to break out of the attribute context and inject arbitrary script. Preconditions: - An authenticated MISP user with the ability to create or modify an event graph entry. - A second user (the victim) who views the event graph and triggers the preview popover. Impact: - Execution of arbitrary JavaScript in the victim's browser within the MISP application context. - Potential theft of session tokens, cookies, or sensitive data accessible to the victim's browser. - Potential for performing actions on behalf of the victim within the MISP application. Affected: MISP versions prior to the fix (commit applied after v2.5.48).

ELEVATED IMPACT

Severe if exploited (CVSS 8.3), but no known exploitation and low modeled probability. Patch on a normal cadence.

Exploitation likelihood

0.4%chance of exploitation in 30 days · 28th percentile

○ In CISA KEV ○ Public exploit / PoC

Impact if exploited

8.3CVSS 4.0 · HIGH

  • ConfidentialityNone
  • IntegrityHigh
  • AvailabilityNone

What an attacker needs

  • ✓Access: Reachable over the network — no local access needed
  • ⚠Privileges: Requires a low-privilege account
  • ⚠User interaction: Succeeds with passive user activity
  • ✓Complexity: No special conditions — reliably repeatable
  • ✓Requirements: No special attack requirements

✓ lowers the bar for an attacker · ⚠ raises it

Proof of concept & exploit code

Test against your own equipment

curl -s https://vulnpedia.com/cve/CVE-2026-103321/poc.jsonMachine-readable PoC index for this CVE (for automation).

Listed for defensive triage, patch verification, and authorized testing on systems you own. Machine-readable: /cve/CVE-2026-103321/poc.json

Affected

Vendors Misp

Products Misp

Weakness (CWE)

  • CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
  • CWE-20: Improper Input Validation

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:H/VA:N/SC:H/SI:H/SA:N

All CVSS metrics

  • HIGH 8.3 v4.0 · CNA Primary
    CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:H/VA:N/SC:H/SI:H/SA:N
  • HIGH 8.3 v4.0 · NVD Secondary
    CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:H/VA:N/SC:H/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

References

Patches & mitigations

Sources: NVD · CVE.org · EPSS