The email module, specifically the "BytesGenerator" class, didn’t properly quote newlines for email headers when serializing an email message allowing for header injection when an email is serialized. This is only applicable if using "LiteralHeader" writing headers that don't respect email folding rules, the new behavior will reject the incorrectly folded headers in "BytesGenerator".
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Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3.1 Vector
No CVSS vector data available.
Exploit Intelligence
0.56%probability of exploitation in 30 days
44thpercentile
Moderate risk: more likely to be exploited than 44% of all known CVEs.
Published advisories record a fix for 93 affected products. The "How to fix" section on this page lists the fixed version and source advisory for each one, so apply the entry matching what you actually run.
Is CVE-2026-1299 being actively exploited?
Not that we know of. CVE-2026-1299 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.56% is the estimated probability that it will be exploited in the next 30 days. That is higher than 44% of all scored CVEs.
What does CVE-2026-1299 affect?
Published advisories record a fix for pypy3 (Debian), platform-python (Rocky), platform-python (Red Hat / RHEL), platform-python-debug (Rocky), and 89 more. Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
TridentStack Control continuously scans your Windows, macOS, and Linux fleet for known vulnerabilities, prioritizes them by severity and active exploitation, and patches them automatically.
This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-02-13.