CVE-2026-125756 postal-mime before 4.2.1 Sender Spoofing via Address Parser Domain Truncation
High 8.2
Published
Updated
Check this codebase for CVE-2026-125756 and fix it if it is affected.
What it is: CVE-2026-125756 is a high-severity vulnerability in postalsys postal-mime, published on 10 Nov 2026.
Exploitation: There is no known exploitation of CVE-2026-125756 in the wild and no public exploit code.
Affected product: postalsys postal-mime. No package-level version data is available, so check the vendor advisory linked from the reference page.
Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.
Reference: https://insights.sbomify.com/CVE-2026-125756/ (Markdown: https://insights.sbomify.com/CVE-2026-125756/index.md)
- Exploited in the wild
- Not known
- Fix
- None listed
What is CVE-2026-125756?
CVE-2026-125756 is a high-severity vulnerability in postalsys postal-mime, published on 10 Nov 2026.
Official description
postal-mime before 4.2.1 contains a parser differential vulnerability in its address parser that truncates the domain at folding whitespace or comments preceding a dot. Remote attackers can craft From headers that pass SPF/DKIM/DMARC alignment for their own subdomain while PostalMime.parse() reports a spoofed victim sender address.
Weakness: CWE-436
Which versions are affected by CVE-2026-125756?
How do I fix CVE-2026-125756?
No fix has been published for CVE-2026-125756 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-125756 being exploited?
There is no known exploitation of CVE-2026-125756 in the wild and no public exploit code.
Sources
Also known as GHSA-jh3p-792r-98gm, GHSA-vpww-qpqr-cgcc.