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Fencer Intel
medium 6.0

CVE-2026-1299 json

email BytesGenerator header injection due to unquoted newlines

published 9mo ago modified 4mo ago also BIT-libpython-2026-1299 , BIT-python-2026-1299 , BIT-python-min-2026-1299 , EUVD-2026-4272

cvss
6.0
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 47%
public exploits
0
none known

Summary

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".

Patch / fix

  • bitnami libpython 3.10.20, 3.11.15, 3.12.13, 3.13.12, 3.14.3
  • bitnami python 3.10.20, 3.11.15, 3.12.13, 3.13.12, 3.14.3
  • bitnami python-min 3.10.20, 3.11.15, 3.12.13, 3.13.12, 3.14.3
  • Python Software Foundation CPython 3.10.20, 3.11.15, 3.12.13, 3.13.12, 3.14.3, 3.15.0a6
  • pypy3 Debian 14 7.3.21+dfsg-1
  • python3.11 Debian 12 3.11.2-6+deb12u7
  • python3.13 Debian 13 3.13.5-2+deb13u1
  • python3.14 Debian 14 3.14.3-1

debian advisories DEBIAN-CVE-2026-1299

  • python3.10 Ubuntu 22.04 LTS 3.10.12-1~22.04.16
  • python3.12 Ubuntu 24.04 LTS 3.12.3-1ubuntu0.15
  • python3.14 Ubuntu 26.04 LTS 3.14.3-1

ubuntu advisories UBUNTU-CVE-2026-1299

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • python3.11 hummingbird 1 3.11.15-4.hum1
  • python3.11-idle hummingbird 1 3.11.15-4.hum1
  • python3.11-libs hummingbird 1 3.11.15-4.hum1
  • python3.11-test hummingbird 1 3.11.15-4.hum1
  • python3.11-tkinter hummingbird 1 3.11.15-4.hum1
  • python3.12 hummingbird 1 3.12.13-3.hum1
  • python3.12-idle hummingbird 1 3.12.13-3.hum1
  • python3.12-libs hummingbird 1 3.12.13-3.hum1

red hat advisories RHSA-2026:8822RHSA-2026:8824RHSA-2026:7661RHSA-2026:7443RHSA-2026:6464RHSA-2026:6253

  • python311 SLES for SAP 15 SP5, SLES for SAP 15 SP4, SLES 15 SP5-LTSS +6 more 3.11.15-150400.9.80.1
  • python311-core SLES for SAP 15 SP5, SLES for SAP 15 SP4, SLES 15 SP5-LTSS +6 more 3.11.15-150400.9.80.1
  • python311-documentation SLES for SAP 15 SP5, SLES for SAP 15 SP4, SLES 15 SP5-LTSS +5 more 3.11.15-150400.9.80.1
  • python313 SLE Module for Python 3 15 SP7 3.13.13-150700.4.45.1
  • python313-core SLE Module for Python 3 15 SP7 3.13.13-150700.4.45.1
  • python311 SLES for SAP 15 SP6, SLES 15 SP6-LTSS, SLE Module for Python 3 15 SP7 +1 more 3.11.15-150600.3.53.1
  • python311-core SLES for SAP 15 SP6, SLES 15 SP6-LTSS, SLE Module for Python 3 15 SP7 +2 more 3.11.15-150600.3.53.1
  • python311-documentation openSUSE Leap 15.6 3.11.15-150600.3.53.1

suse advisories SUSE-SU-2026:1117-1SUSE-SU-2026:1354-1SUSE-SU-2026:1349-1SUSE-SU-2026:21104-1SUSE-SU-2026:21178-1SUSE-SU-2026:20951-1

  • python313 openSUSE Leap 16.0 3.13.13-160000.1.1
  • python313-core openSUSE Leap 16.0 3.13.13-160000.1.1
  • python313-nogil openSUSE Leap 16.0 3.13.13-160000.1.1
  • python313-documentation openSUSE Leap 16.0 3.13.13-160000.1.1
  • python313-nogil-nogil-core openSUSE Leap 16.0 3.13.13-160000.1.1
  • python310 openSUSE Tumbleweed 3.10.20-2.1
  • python311 openSUSE Tumbleweed 3.11.15-3.1
  • python313 openSUSE Leap 16.0 3.13.12-160000.1.1

opensuse advisories openSUSE-SU-2026:20517-1openSUSE-SU-2026:10404-1openSUSE-SU-2026:10398-1openSUSE-SU-2026:20254-1openSUSE-SU-2026:10222-1openSUSE-SU-2026:10223-1

  • python-unversioned-command AlmaLinux 10 3.12.12-3.el10_1.1
  • python3.12 AlmaLinux 8 3.12.12-3.el8_10
  • python3.12-idle AlmaLinux 8 3.12.12-3.el8_10
  • python3.12-libs AlmaLinux 8 3.12.12-3.el8_10
  • python3.12-test AlmaLinux 8 3.12.12-3.el8_10
  • python3.12-tkinter AlmaLinux 8 3.12.12-3.el8_10
  • python3.12-rpm-macros AlmaLinux 8 3.12.12-3.el8_10
  • python3.11 AlmaLinux 8 3.11.13-5.el8_10

almalinux advisories ALSA-2026:4713ALSA-2026:4463ALSA-2026:4473ALSA-2026:4165ALSA-2026:4168ALSA-2026:4216

  • python3 Rocky Linux 8 3.6.8-73.el8_10.rocky.0
  • python3.12 Rocky Linux 10 3.12.12-3.el10_1.1
  • python3.11 Rocky Linux 8 3.11.13-5.el8_10
  • python3.12 Rocky Linux 8 3.12.12-3.el8_10
  • python3.11 Rocky Linux 9 3.11.13-5.1.el9_7
  • python3.12 Rocky Linux 9 3.12.12-4.el9_7.1
  • python3.9 Rocky Linux 9 3.9.25-3.el9_7.1

rocky linux advisories RLSA-2026:2128RLSA-2026:4713RLSA-2026:4473RLSA-2026:4463RLSA-2026:4216RLSA-2026:4165

  • python3 CBL-Mariner 2.0 3.9.19-18
  • python3 Azure Linux 3.0 3.12.9-9

azure linux advisories AZL-75219AZL-75234

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Is CVE-2026-1299 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-1299 updated cvss 7.1

cpython: email header injection due to unquoted newlines

  • Red Hat Enterprise Linux 9 python3.14, python3.14-idle, python3.14-libs, python3.14-test, python3.14-tkinter, python3.14-freethreading, +4 more Red Hat Enterprise Linux 10 python3.14
    affected: workaround, no fix available
  • Red Hat Enterprise Linux AI (RHEL AI) 3 rhelai3/bootc-cuda-rhel9, rhelai3/bootc-aws-cuda-rhel9, rhelai3/bootc-gcp-cuda-rhel9, rhelai3/bootc-azure-cuda-rhel9
    affected: workaround, no fix planned “Will not fix”
  • Red Hat AI Inference Server 3.3 rhaiis 1775680192, rhaiis 1775680262, rhaiis 1775749857, rhaiis 1778244546
    fixed: vendor fix RHSA-2026:8748
  • Red Hat Ceph Storage 8 rhceph 1774002867
    fixed: vendor fix RHSA-2026:5606
  • Red Hat CodeReady Linux Builder EUS (v.9.4) python3 3.9.18-3.el9_4.11, python3.11 3.11.7-1.el9_4.11, python3.12 3.12.1-4.el9_4.11, python3-idle 3.9.18-3.el9_4.11, python3-test 3.9.18-3.el9_4.11, python3-tkinter 3.9.18-3.el9_4.11, +6 more
    fixed: vendor fix RHSA-2026:5226
  • Red Hat CodeReady Linux Builder EUS (v.9.6) python3 3.9.21-2.el9_6.4, python3.12 3.12.9-1.el9_6.6, python3-idle 3.9.21-2.el9_6.4, python3-test 3.9.21-2.el9_6.4, python3-tkinter 3.9.21-2.el9_6.4, python3.12-idle 3.12.9-1.el9_6.6, +2 more
    fixed: vendor fix RHSA-2026:5218
  • Red Hat Discovery 2 discovery 1775668717, discovery 1775675922
    fixed: vendor fix RHSA-2026:7329
  • Red Hat Enterprise Linux AppStream (v. 8) python3.11 3.11.13-5.el8_10, python3.12 3.12.12-3.el8_10, python3-idle 3.6.8-73.el8_10, python3-test 3.6.8-73.el8_10, platform-python 3.6.8-73.el8_10, python3-tkinter 3.6.8-73.el8_10, +6 more
    fixed: vendor fix RHSA-2026:2128
show 29 more
  • Red Hat Enterprise Linux AppStream (v. 9) python3.11 3.11.13-5.1.el9_7, python3.12 3.12.12-4.el9_7.1, python3-tkinter 3.9.25-3.el9_7.1, python3.11-libs 3.11.13-5.1.el9_7, python3.12-libs 3.12.12-4.el9_7.1, python3.11-tkinter 3.11.13-5.1.el9_7, +2 more
    fixed: vendor fix RHSA-2026:4168
  • Red Hat Enterprise Linux AppStream (v. 10) python3-tkinter 3.12.12-3.el10_1.1, python-unversioned-command 3.12.12-3.el10_1.1
    fixed: vendor fix RHSA-2026:4713
  • Red Hat Enterprise Linux AppStream AUS (v. 8.2) python3-idle 3.6.8-24.el8_2.6, python3-test 3.6.8-24.el8_2.6, platform-python 3.6.8-24.el8_2.6, python3-tkinter 3.6.8-24.el8_2.6
    fixed: vendor fix RHSA-2026:5216
  • Red Hat Enterprise Linux AppStream AUS (v.8.4) python3-idle 3.6.8-39.el8_4.9, python3-test 3.6.8-39.el8_4.9, platform-python 3.6.8-39.el8_4.9, python3-tkinter 3.6.8-39.el8_4.9
    fixed: vendor fix RHSA-2026:5221
  • Red Hat Enterprise Linux AppStream AUS (v.8.6) python3-idle 3.6.8-47.el8_6.11, python3-test 3.6.8-47.el8_6.11, platform-python 3.6.8-47.el8_6.11, python3-tkinter 3.6.8-47.el8_6.11 Red Hat Enterprise Linux AppStream E4S (v.8.6) python3-idle 3.6.8-47.el8_6.11, python3-test 3.6.8-47.el8_6.11, platform-python 3.6.8-47.el8_6.11, python3-tkinter 3.6.8-47.el8_6.11
    fixed: vendor fix RHSA-2026:5215
  • Red Hat Enterprise Linux AppStream E4S (v.8.8) python3.11 3.11.2-2.el8_8.8, python3-idle 3.6.8-51.el8_8.13, python3-test 3.6.8-51.el8_8.13, python3.11-libs 3.11.2-2.el8_8.8, platform-python 3.6.8-51.el8_8.13, python3-tkinter 3.6.8-51.el8_8.13, +2 more
    fixed: vendor fix RHSA-2026:6008
  • Red Hat Enterprise Linux AppStream E4S (v.9.0) python3-tkinter 3.9.10-4.el9_0.9, python-unversioned-command 3.9.10-4.el9_0.9
    fixed: vendor fix RHSA-2026:5219
  • Red Hat Enterprise Linux AppStream E4S (v.9.2) python3.11 3.11.2-2.el9_2.10, python3-tkinter 3.9.16-1.el9_2.12, python3.11-libs 3.11.2-2.el9_2.10, python3.11-tkinter 3.11.2-2.el9_2.10, python-unversioned-command 3.9.16-1.el9_2.12
    fixed: vendor fix RHSA-2026:5225
  • Red Hat Enterprise Linux AppStream EUS (v. 10.0) python3-tkinter 3.12.9-2.el10_0.7, python-unversioned-command 3.12.9-2.el10_0.7
    fixed: vendor fix RHSA-2026:5315
  • Red Hat Enterprise Linux AppStream EUS (v.9.4) python3.11 3.11.7-1.el9_4.11, python3.12 3.12.1-4.el9_4.11, python3-tkinter 3.9.18-3.el9_4.11, python3.11-libs 3.11.7-1.el9_4.11, python3.12-libs 3.12.1-4.el9_4.11, python3.11-tkinter 3.11.7-1.el9_4.11, +2 more
    fixed: vendor fix RHSA-2026:5226
  • Red Hat Enterprise Linux AppStream EUS (v.9.6) python3.12 3.12.9-1.el9_6.6, python3-tkinter 3.9.21-2.el9_6.4, python3.12-libs 3.12.9-1.el9_6.6, python3.12-tkinter 3.12.9-1.el9_6.6, python-unversioned-command 3.9.21-2.el9_6.4
    fixed: vendor fix RHSA-2026:5218
  • Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4) python3-idle 3.6.8-39.el8_4.9, python3-test 3.6.8-39.el8_4.9, platform-python 3.6.8-39.el8_4.9, python3-tkinter 3.6.8-39.el8_4.9
    fixed: vendor fix RHSA-2026:5221
  • Red Hat Enterprise Linux AppStream TUS (v.8.6) python3-idle 3.6.8-47.el8_6.11, python3-test 3.6.8-47.el8_6.11, platform-python 3.6.8-47.el8_6.11, python3-tkinter 3.6.8-47.el8_6.11
    fixed: vendor fix RHSA-2026:5215
  • Red Hat Enterprise Linux AppStream TUS (v.8.8) python3.11 3.11.2-2.el8_8.8, python3-idle 3.6.8-51.el8_8.13, python3-test 3.6.8-51.el8_8.13, python3.11-libs 3.11.2-2.el8_8.8, platform-python 3.6.8-51.el8_8.13, python3-tkinter 3.6.8-51.el8_8.13, +2 more
    fixed: vendor fix RHSA-2026:6008
  • Red Hat Enterprise Linux BaseOS (v. 8) python3 3.6.8-73.el8_10, python3-libs 3.6.8-73.el8_10, python3-test 3.6.8-73.el8_10, platform-python 3.6.8-73.el8_10
    fixed: vendor fix RHSA-2026:2128
  • Red Hat Enterprise Linux BaseOS (v. 9) python3 3.9.25-3.el9_7.1, python3.9 3.9.25-3.el9_7.1, python3-libs 3.9.25-3.el9_7.1
    fixed: vendor fix RHSA-2026:4168
  • Red Hat Enterprise Linux BaseOS (v. 10) python3 3.12.12-3.el10_1.1, python3.12 3.12.12-3.el10_1.1, python3-libs 3.12.12-3.el10_1.1
    fixed: vendor fix RHSA-2026:4713
  • Red Hat Enterprise Linux BaseOS AUS (v. 8.2) python3 3.6.8-24.el8_2.6, python3-libs 3.6.8-24.el8_2.6, python3-test 3.6.8-24.el8_2.6, platform-python 3.6.8-24.el8_2.6
    fixed: vendor fix RHSA-2026:5216
  • Red Hat Enterprise Linux BaseOS AUS (v.8.4) python3 3.6.8-39.el8_4.9, python3-libs 3.6.8-39.el8_4.9, python3-test 3.6.8-39.el8_4.9, platform-python 3.6.8-39.el8_4.9
    fixed: vendor fix RHSA-2026:5221
  • Red Hat Enterprise Linux BaseOS AUS (v.8.6) python3 3.6.8-47.el8_6.11, python3-libs 3.6.8-47.el8_6.11, python3-test 3.6.8-47.el8_6.11, platform-python 3.6.8-47.el8_6.11 Red Hat Enterprise Linux BaseOS E4S (v.8.6) python3 3.6.8-47.el8_6.11, python3-libs 3.6.8-47.el8_6.11, python3-test 3.6.8-47.el8_6.11, platform-python 3.6.8-47.el8_6.11
    fixed: vendor fix RHSA-2026:5215
  • Red Hat Enterprise Linux BaseOS E4S (v.8.8) python3 3.6.8-51.el8_8.13, python3-libs 3.6.8-51.el8_8.13, python3-test 3.6.8-51.el8_8.13, platform-python 3.6.8-51.el8_8.13
    fixed: vendor fix RHSA-2026:6008
  • Red Hat Enterprise Linux BaseOS E4S (v.9.0) python3 3.9.10-4.el9_0.9, python3.9 3.9.10-4.el9_0.9, python3-libs 3.9.10-4.el9_0.9
    fixed: vendor fix RHSA-2026:5219
  • Red Hat Enterprise Linux BaseOS E4S (v.9.2) python3 3.9.16-1.el9_2.12, python3.9 3.9.16-1.el9_2.12, python3-libs 3.9.16-1.el9_2.12
    fixed: vendor fix RHSA-2026:5225
  • Red Hat Enterprise Linux BaseOS EUS (v. 10.0) python3 3.12.9-2.el10_0.7, python3.12 3.12.9-2.el10_0.7, python3-libs 3.12.9-2.el10_0.7
    fixed: vendor fix RHSA-2026:5315
  • Red Hat Enterprise Linux BaseOS EUS (v.9.4) python3 3.9.18-3.el9_4.11, python3.9 3.9.18-3.el9_4.11, python3-libs 3.9.18-3.el9_4.11
    fixed: vendor fix RHSA-2026:5226
  • Red Hat Enterprise Linux BaseOS EUS (v.9.6) python3 3.9.21-2.el9_6.4, python3.9 3.9.21-2.el9_6.4, python3-libs 3.9.21-2.el9_6.4
    fixed: vendor fix RHSA-2026:5218
  • Red Hat Enterprise Linux BaseOS EUS EXTENSION (v.8.4) python3 3.6.8-39.el8_4.9, python3-libs 3.6.8-39.el8_4.9, python3-test 3.6.8-39.el8_4.9, platform-python 3.6.8-39.el8_4.9
    fixed: vendor fix RHSA-2026:5221
  • Red Hat Enterprise Linux BaseOS TUS (v.8.6) python3 3.6.8-47.el8_6.11, python3-libs 3.6.8-47.el8_6.11, python3-test 3.6.8-47.el8_6.11, platform-python 3.6.8-47.el8_6.11
    fixed: vendor fix RHSA-2026:5215
  • Red Hat Enterprise Linux BaseOS TUS (v.8.8) python3 3.6.8-51.el8_8.13, python3-libs 3.6.8-51.el8_8.13, python3-test 3.6.8-51.el8_8.13, platform-python 3.6.8-51.el8_8.13
    fixed: vendor fix RHSA-2026:6008

8 more fixed, 7 more not affected in the full advisory

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
9mo ago

Exploit prediction

0.57% chance of exploitation in the next 30 days, higher than 47% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 4.0 6.0 CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:L/VI:H/VA:N/SC:N/SI:N/SA:N
CNA 4.0 6.0 CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:L/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected packages

ecosystem package affected fixed in
bitnami libpython
<3.10.20
>=3.11.0, <3.11.15
>=3.12.0, <3.12.13
>=3.13.0, <3.13.12
>=3.14.0, <3.14.3
3.10.20
3.11.15
3.12.13
3.13.12
3.14.3
bitnami python
<3.10.20
>=3.11.0, <3.11.15
>=3.12.0, <3.12.13
>=3.13.0, <3.13.12
>=3.14.0, <3.14.3
3.10.20
3.11.15
3.12.13
3.13.12
3.14.3
bitnami python-min
<3.10.20
>=3.11.0, <3.11.15
>=3.12.0, <3.12.13
>=3.13.0, <3.13.12
>=3.14.0, <3.14.3
3.10.20
3.11.15
3.12.13
3.13.12
3.14.3

Affected products

  • Python Software Foundation CPython

Classification

Weakness
  • CWE-93 Improper Neutralization of CRLF Sequences

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.