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Full vulnerability report · 2026
CVE-2026-6019High confidence

BaseCookie.js_output() does not neutralize embedded characters

Python Software Foundation · CPython

2.1LowCVSS 4.0
Recommended action
Within 7 days

Low technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance.

Patch available
Distribution package intelligence

Ubuntu vendor package status

Canonical’s release and source-package findings are shown separately from local repository availability.

2 package states
Repository candidate not checked

A published vendor fix does not prove that a matching update is enabled and installable on a particular asset. Confirm the local package candidate before scheduling remediation.

Ubuntu releaseSource packageVendor stateFixed versionEvidence
Ubuntu 24.04 LTSnoble · standard archivepypy3Under evaluationCanonical reports that the package might be affected and still needs evaluation or fixing.Not published in this feedCanonical record ↗Source updated 9 Sept 2026
Ubuntu 24.04 LTSnoble · standard archivepython3.12Vendor fix publishedCanonical reports that a fixed source package version has been published. Repository candidate availability is not checked by BlackTree.3.12.3-1ubuntu0.15Canonical record ↗Source updated 9 Sept 2026
Direct vendor intelligence

Authoritative vendor CSAF and VEX advisories

Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.

1 current
CVE-2026-6019 · CSAF 2.0 · revision 3 · finalRed Hat Product Securitypython: Python: Cross-Site Scripting (XSS) vulnerability in http.cookies module
185 known affected

The vendor explicitly identifies these products as affected by this CVE.

  • python-unversioned-command as a component of Red Hat Enterprise Linux 10
  • python3 as a component of Red Hat Enterprise Linux 10
  • python3-debug as a component of Red Hat Enterprise Linux 10
  • python3-devel as a component of Red Hat Enterprise Linux 10
  • python3-idle as a component of Red Hat Enterprise Linux 10
  • python3-libs as a component of Red Hat Enterprise Linux 10
  • python3-test as a component of Red Hat Enterprise Linux 10
  • python3-tkinter as a component of Red Hat Enterprise Linux 10
  • python3.12.src as a component of Red Hat Enterprise Linux 10
  • python as a component of Red Hat Enterprise Linux 6
  • python-devel as a component of Red Hat Enterprise Linux 6
  • python-libs as a component of Red Hat Enterprise Linux 6
Summary
A flaw was found in Python's `http.cookies` module. The `Morsel.js_output()` function, responsible for generating JavaScript output for cookies, does not properly neutralize the ` ` HTML sequence. This oversight could allow a remote attacker to inject malicious script into a web page, potentially leading to Cross-Site Scripting (XSS) attacks. Such an attack could result in information disclosure or arbitrary code execution within the user's browser.
Remediation
For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Select the national-authority views to include. The exact source language is shown on each matched advisory. Your choice is remembered on this device and encoded in the shareable URL.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2026-25079

No EUVD known-exploited evidence

ENISA has published the identifier mapping but no EUVD description has been stored yet.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
Not supplied in the stored EUVD record
Advisory evidence
No linked advisory details stored yet
Recommended actionWithin 7 days

Low technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance.

Patch available
01

What, why and how

http.cookies.Morsel.js_output() returns an inline <script> snippet and only escapes " for JavaScript string context. It does not neutralize the HTML parser-sensitive sequence </script> inside the generated script element. Mitigation base64-encodes the cookie value to disallow escaping using cookie value.

What

http.cookies.Morsel.js_output() returns an inline <script> snippet and only escapes " for JavaScript string context. It does not neutralize the HTML parser-sensitive sequence </script> inside the generated script element. Mitigation base64-encodes the cookie value to disallow escaping using cookie value.

Why

The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could be interpreted as escape, meta, or control character sequences when they are sent to a downstream component.

How

An attacker operating through a network path may attempt exploitation with elevated privileges. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

What

http.cookies.Morsel.js_output() returns an inline <script> snippet and only escapes " for JavaScript string context. It does not neutralize the HTML parser-sensitive sequence </script> inside the generated script element. Mitigation base64-encodes the cookie value to disallow escaping using cookie value.

Why

The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could be interpreted as escape, meta, or control character sequences when they are sent to a downstream component.

How

An attacker operating through a network path may attempt exploitation with elevated privileges. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
Reference recorded

A structured CVE source labels at least one public reference as exploit material. BlackTree has not independently validated that it is safe, reliable or weaponised.

Likely attack path
a network path → Improper Neutralization of Escape, Meta, or Control Sequences → cause the confidentiality, integrity or availability impact described by the vendor
Attack surface
Network
Privileges required
High: elevated access is required
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Not a CVSS 4.0 base metric
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-150 ↗

CWE-150: Improper Neutralization of Escape, Meta, or Control Sequences. The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could be interpreted as escape, meta, or control character sequences when they are sent to a downstream component.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N

Common Vulnerability Scoring System 4.0: the compact vector below is decoded into plain language.

AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.ATPresentAttack requirements: A particular deployment or execution condition must be present.PRHighPrivileges required: The attacker needs elevated or administrative privileges.UINoneUser interaction: No action by another user is required.VCLowVulnerable-system confidentiality: A successful attack can cause a limited loss.VILowVulnerable-system integrity: A successful attack can cause a limited loss.VANoneVulnerable-system availability: No direct loss is represented by this metric.SCNoneSubsequent-system confidentiality: No direct loss is represented by this metric.SINoneSubsequent-system integrity: No direct loss is represented by this metric.SANoneSubsequent-system availability: No direct loss is represented by this metric.
Post-exploitation / living off the land
No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
NetworkCWE-150Public exploit reference
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

BSI · German · WID-SEC-W-2026-2455Oracle Solaris Drittanbieterkomponenten: Mehrere Schwachstellen

Ein entfernter, anonymer oder authentisierter Angreifer kann mehrere Schwachstellen in verschiedenen Komponenten von Drittanbietern in Oracle Solaris ausnutzen, um einen nicht näher spezifizierten Angriff durchzuführen.

Official advisory
CERT-FR · French · CERTFR-2026-AVI-0482Vulnérabilité dans CPython

Une vulnérabilité a été découverte dans CPython. Elle permet à un attaquant de provoquer un contournement de la politique de sécurité.

Official advisory
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Patch available
Affected
python-unversioned-command as a component of Red Hat Enterprise Linux 10; python3 as a component of Red Hat Enterprise Linux 10; python3-debug as a component of Red Hat Enterprise Linux 10; python3-devel as a component of Red Hat Enterprise Linux 10; python3-idle as a component of Red Hat Enterprise Linux 10; python3-libs as a component of Red Hat Enterprise Linux 10; python3-test as a component of Red Hat Enterprise Linux 10; python3-tkinter as a component of Red Hat Enterprise Linux 10; python3.12.src as a component of Red Hat Enterprise Linux 10; python as a component of Red Hat Enterprise Linux 6; python-devel as a component of Red Hat Enterprise Linux 6; python-libs as a component of Red Hat Enterprise Linux 6; python-test as a component of Red Hat Enterprise Linux 6; python-tools as a component of Red Hat Enterprise Linux 6; python.src as a component of Red Hat Enterprise Linux 6; tkinter as a component of Red Hat Enterprise Linux 6; python as a component of Red Hat Enterprise Linux 7; python-debug as a component of Red Hat Enterprise Linux 7; python-devel as a component of Red Hat Enterprise Linux 7; python-libs as a component of Red Hat Enterprise Linux 7; python-test as a component of Red Hat Enterprise Linux 7; python-tools as a component of Red Hat Enterprise Linux 7; python.src as a component of Red Hat Enterprise Linux 7; python3 as a component of Red Hat Enterprise Linux 7; python3-debug as a component of Red Hat Enterprise Linux 7; python3-devel as a component of Red Hat Enterprise Linux 7; python3-idle as a component of Red Hat Enterprise Linux 7; python3-libs as a component of Red Hat Enterprise Linux 7; python3-test as a component of Red Hat Enterprise Linux 7; python3-tkinter as a component of Red Hat Enterprise Linux 7; and 155 more
Fixed
python3.14-0:3.14.5-1.el10_2.aarch64 as a component of Red Hat Enterprise Linux AppStream (v. 10); python3.14-0:3.14.5-1.el10_2.ppc64le as a component of Red Hat Enterprise Linux AppStream (v. 10); python3.14-0:3.14.5-1.el10_2.s390x as a component of Red Hat Enterprise Linux AppStream (v. 10); python3.14-0:3.14.5-1.el10_2.src as a component of Red Hat Enterprise Linux AppStream (v. 10); python3.14-0:3.14.5-1.el10_2.x86_64 as a component of Red Hat Enterprise Linux AppStream (v. 10); python3.14-debuginfo-0:3.14.5-1.el10_2.aarch64 as a component of Red Hat Enterprise Linux AppStream (v. 10); python3.14-debuginfo-0:3.14.5-1.el10_2.ppc64le as a component of Red Hat Enterprise Linux AppStream (v. 10); python3.14-debuginfo-0:3.14.5-1.el10_2.s390x as a component of Red Hat Enterprise Linux AppStream (v. 10); python3.14-debuginfo-0:3.14.5-1.el10_2.x86_64 as a component of Red Hat Enterprise Linux AppStream (v. 10); python3.14-debugsource-0:3.14.5-1.el10_2.aarch64 as a component of Red Hat Enterprise Linux AppStream (v. 10); python3.14-debugsource-0:3.14.5-1.el10_2.ppc64le as a component of Red Hat Enterprise Linux AppStream (v. 10); python3.14-debugsource-0:3.14.5-1.el10_2.s390x as a component of Red Hat Enterprise Linux AppStream (v. 10); python3.14-debugsource-0:3.14.5-1.el10_2.x86_64 as a component of Red Hat Enterprise Linux AppStream (v. 10); python3.14-devel-0:3.14.5-1.el10_2.aarch64 as a component of Red Hat Enterprise Linux AppStream (v. 10); python3.14-devel-0:3.14.5-1.el10_2.ppc64le as a component of Red Hat Enterprise Linux AppStream (v. 10); python3.14-devel-0:3.14.5-1.el10_2.s390x as a component of Red Hat Enterprise Linux AppStream (v. 10); python3.14-devel-0:3.14.5-1.el10_2.x86_64 as a component of Red Hat Enterprise Linux AppStream (v. 10); python3.14-libs-0:3.14.5-1.el10_2.aarch64 as a component of Red Hat Enterprise Linux AppStream (v. 10); python3.14-libs-0:3.14.5-1.el10_2.ppc64le as a component of Red Hat Enterprise Linux AppStream (v. 10); python3.14-libs-0:3.14.5-1.el10_2.s390x as a component of Red Hat Enterprise Linux AppStream (v. 10); python3.14-libs-0:3.14.5-1.el10_2.x86_64 as a component of Red Hat Enterprise Linux AppStream (v. 10); python3.14-tkinter-0:3.14.5-1.el10_2.aarch64 as a component of Red Hat Enterprise Linux AppStream (v. 10); python3.14-tkinter-0:3.14.5-1.el10_2.ppc64le as a component of Red Hat Enterprise Linux AppStream (v. 10); python3.14-tkinter-0:3.14.5-1.el10_2.s390x as a component of Red Hat Enterprise Linux AppStream (v. 10); python3.14-tkinter-0:3.14.5-1.el10_2.x86_64 as a component of Red Hat Enterprise Linux AppStream (v. 10); python3.14-0:3.14.5-1.el9_8.aarch64 as a component of Red Hat Enterprise Linux AppStream (v. 9); python3.14-0:3.14.5-1.el9_8.ppc64le as a component of Red Hat Enterprise Linux AppStream (v. 9); python3.14-0:3.14.5-1.el9_8.s390x as a component of Red Hat Enterprise Linux AppStream (v. 9); python3.14-0:3.14.5-1.el9_8.src as a component of Red Hat Enterprise Linux AppStream (v. 9); python3.14-0:3.14.5-1.el9_8.x86_64 as a component of Red Hat Enterprise Linux AppStream (v. 9); and 147 more
Action
For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258
Workaround
No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04

Evidence and provenance

Published 22 Apr 2026 · Last source change 10 Jun 2026, 18:58 UTC · CWE-150 · Improper Neutralization of Escape, Meta, or Control Sequences

CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2026-25079
Product sourceVendor CSAF · Red Hat Product Security
Remediation sourceVendor CSAF · Red Hat Product Security
CWE sourceCNA
NVD statusNVD enriched

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates →

No material field changes have been recorded since change tracking began. Routine source refreshes and cosmetic edits are intentionally excluded.

Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release or patch reference recorded
ENISA EUVD · EUVD-2026-25079↗Vendor CSAF · Red Hat Product Security↗CVE authority or vendor reference↗Vendor advisory↗Patch or update reference↗Patch or update reference↗Public exploit reference↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2026-6019 · cve.blacktree.nl