How severe is CVE-2026-3455?

No CVSS score has been assigned to CVE-2026-3455 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-3455?

CVE-2026-3455 affects the following packages: mailparser (npm). Ecosystems affected: npm.

How do I fix CVE-2026-3455?

Update mailparser to 3.9.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-3455 is resolved across your whole dependency graph.

How do I detect CVE-2026-3455 in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for mailparser, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-3455 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against CVE-2026-3455?

O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-3455 can be triaged on real exposure rather than presence alone.

Is CVE-2026-3455 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-3455 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-3455?

CVE-2026-3455 has an EPSS (Exploit Prediction Scoring System) score of 0.3%, placing it in the 24th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-3455?

CVE-2026-3455 is classified as Cross-site Scripting (XSS) (CWE-79). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2026-3455 published, and has it been updated?

CVE-2026-3455 was published on March 3, 2026 and was last updated on August 12, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦 npm

Not in CISA KEV

CVE-2026-3455 — mailparser

Fix: nodemailer/mailparser@921a67d

CVE-2026-3455 is a Cross-site Scripting (XSS) vulnerability in mailparser. A fix is available for mailparser — see the affected versions and patch details below.

mailparser vulnerable to Cross-site Scripting

Also known asGHSA-7gmj-h9xc-mcxc

Published

Mar 3, 2026

Updated

Aug 12, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Sep 21, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

Proof-of-concept exploit code exists

CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-3455.

EPSS Exploitation Probability

via FIRST.org ↗

0.3%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs24th percentile — riskier than 24% of all scored CVEsHighest risk

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

1Kother npm packages depend on this — each one inherits the vulnerability until it's patched upstream

mailparsernpm

4.2Mdownloads / week

Description

Versions of the package mailparser before 3.9.3 are vulnerable to Cross-site Scripting (XSS) via the textToHtml() function due to the improper sanitisation of URLs in the email content. An attacker can execute arbitrary scripts in victim browsers by adding extra quote " to the URL with embedded malicious JavaScript code.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`mailparser`	all versions	3.9.3`npm install mailparser@3.9.3`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for mailparser, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update mailparser to 3.9.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-3455 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-3455 can be triaged on real exposure rather than presence alone.

Tailored to CVE-2026-3455. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

O3 Security · Impact-Aware SCA

Is CVE-2026-3455 in your dependencies?

O3 Security finds CVE-2026-3455 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.

Scan my dependencies How O3 SCA works