CVE-2026-1299
CVE-2026-1299 is a medium-severity vulnerability with a CVSS 4.0 base score of 6.0. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-93.
Key facts
- Severity: Medium (CVSS 4.0 base score 6.0)
- EPSS exploit prediction: 1% (43rd percentile)
- Actively exploited: Not listed in CISA KEV
- EU (EUVD) id: EUVD-2026-4272
- Weakness: CWE-93
- Published:
- Last modified:
Description
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".
Frequently asked questions
- What is CVE-2026-1299?
- 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".
- How severe is CVE-2026-1299?
- CVE-2026-1299 has a CVSS 4.0 base score of 6.0, rated medium severity.
- Is CVE-2026-1299 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (43rd percentile), an estimate of the probability of exploitation in the next 30 days.
- How do I fix CVE-2026-1299?
- Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
- Does CVE-2026-1299 have an EU (EUVD) identifier?
- Yes. CVE-2026-1299 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-4272.
- When was CVE-2026-1299 published?
- CVE-2026-1299 was published on 2026-01-23 and last updated on 2026-06-17.
References
- https://cve.org/CVERecord?id=CVE-2024-6923
- https://github.com/python/cpython/commit/052e55e7d44718fe46cbba0ca995cb8fcc359413
- https://github.com/python/cpython/commit/0a925ab591c45d6638f37b5e57796f36fa0e56d8
- https://github.com/python/cpython/commit/7877fe424415bc4a13045e62a90a7277413d8cb9
- https://github.com/python/cpython/commit/842ce19a0c0b58d61591e8f6a708c38db1fb94e4
- https://github.com/python/cpython/commit/8cdf6204f4ae821f32993f8fc6bad0d318f95f36
- https://github.com/python/cpython/commit/e417f05ad77a4c30ddc07f99e90fc0cef43e831a
- https://github.com/python/cpython/issues/144125
- https://github.com/python/cpython/pull/144126
- https://mail.python.org/archives/list/[email protected]/thread/6ZZULGALJTITEAGEXLDJE2C6FORDXPBT/
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