Bug 2432437 (CVE-2026-1299)

Summary: CVE-2026-1299 cpython: email header injection due to unquoted newlines
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: bbrownin, dfreiber, drow, gotiwari, jburrell, jgrulich, jhorak, jkoehler, ljawale, lphiri, luizcosta, mvyas, nweather, rbobbitt, sdawley, teagle, tpopela, vkumar
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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Doc Text:
A flaw was found in the email module in the Python standard library. When serializing an email message, the BytesGenerator class fails to properly quote newline characters for email headers. This issue is exploitable when the LiteralHeader class is used as it does not respect email folding rules, allowing an attacker to inject email headers and potentially modify message recipients or the email body, and spoof sender information.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
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Bug Depends On: 2433810, 2433813, 2433815, 2433816, 2433817, 2433818, 2433820, 2433822, 2433823, 2433825, 2433826, 2433827, 2433828, 2433830, 2433832, 2433811, 2433812, 2433814, 2433819, 2433821, 2433824, 2433829, 2433831    
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Description OSIDB Bzimport 2026-01-23 17:03:23 UTC 
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".
Comment 2 errata-xmlrpc 2026-02-05 15:34:34 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2026:2128 https://access.redhat.com/errata/RHSA-2026:2128