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Full vulnerability report · 2026
CVE-2026-3644High confidence

Incomplete control character validation in http.cookies

Python Software Foundation · CPython

6.0MediumCVSS 4.0
Recommended action
Patch only the product branches with a verified fix

Medium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority. Verified remediation exists for at least one product or source, but 1 structured product or package state remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Fix availability varies by product
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityMediumOperational priority:Medium, unchanged from published severity.unchanged

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • EPSS is 0.48% for the current model date.

Compensating controls

  • Validate the affected product branch and deploy the verified fixed release.
  • Restrict the affected network interface to trusted sources where business-safe.
  • Monitor vendor guidance and exploitation sources for a material change.

Verification

  1. Confirm that the asset runs Python Software Foundation CPython and falls inside the recorded affected range.
  2. Verify the installed build against the product-specific fixed version after deployment.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: As exposure requiresRemediation target: Within 365 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Cross-source reconciliation

Remediation availability differs by product scope

Verified remediation exists for at least one product or source, but 1 structured product or package state remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Distribution package intelligence

Release-specific package status

Alpine, Debian, ubuntu findings are scoped to the named distribution, release and source package. An absent finding does not mean a package is unaffected.

10 package states
Package result overrides the generic status

BlackTree has verified remediation for at least one product or source, but the relevant distribution still reports no fixed package for 1 affected package state shown here. Treat those rows as affected with no fix until that distribution publishes a fixed version.

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.

Distribution releaseSource packageVendor stateFixed versionEvidence
Alpine v3.23v3.23 · mainpython3Vendor fix publishedAlpine records a security fix at this version. An absent entry does not mean the package is unaffected.3.12.14-r0Alpine Security Database ↗Source updated 3 Oct 2026
Alpine v3.22v3.22 · mainpython3Vendor fix publishedAlpine records a security fix at this version. An absent entry does not mean the package is unaffected.3.12.14-r0Alpine Security Database ↗Source updated 3 Oct 2026
Alpine v3.21v3.21 · mainpython3Vendor fix publishedAlpine records a security fix at this version. An absent entry does not mean the package is unaffected.3.12.14-r0Alpine Security Database ↗Source updated 3 Oct 2026
Debian trixietrixie · sourcepython3.13Vendor fix publishedDebian records a fixed source-package version for this release.3.13.5-2+deb13u2Debian Security Tracker ↗Source updated 6 Oct 2026
Debian bookwormbookworm · sourcepython3.11Affected, no fix publishedDebian currently tracks this release as open.Not published in this feedDebian Security Tracker ↗Source updated 6 Oct 2026
Debian forkyforky · sourcepython3.13Vendor fix publishedDebian records a fixed source-package version for this release.3.13.14-1Debian Security Tracker ↗Source updated 6 Oct 2026
Debian forkyforky · sourcepython3.14Vendor fix publishedDebian records a fixed source-package version for this release.3.14.3-4Debian Security Tracker ↗Source updated 6 Oct 2026
Debian sidsid · sourcepython3.13Vendor fix publishedDebian records a fixed source-package version for this release.3.13.14-1Debian Security Tracker ↗Source updated 6 Oct 2026
Debian sidsid · sourcepython3.14Vendor fix publishedDebian records a fixed source-package version for this release.3.14.3-4Debian Security Tracker ↗Source updated 6 Oct 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 Ubuntu Security ↗Source updated 5 Oct 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-2026-3644 · CSAF 2.0 · revision 3 · finalRed Hat Product Securitycpython: Incomplete control character validation in http.cookies
156 known affected

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

  • 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
Summary
A control character validation flaw has been discovered in the Python http.cookie module. The Morsel.update(), |= operator, and unpickling paths were not patched to resolve CVE-2026-0672, allowing control characters to bypass input validation. Additionally, BaseCookie.js_output() lacked the output validation applied to BaseCookie.output().
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.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

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-2026-12484

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 actionPatch only the product branches with a verified fix

Medium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority. Verified remediation exists for at least one product or source, but 1 structured product or package state remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Fix availability varies by product
01

What, why and how

The fix for CVE-2026-0672, which rejected control characters in http.cookies.Morsel, was incomplete. The Morsel.update(), |= operator, and unpickling paths were not patched, allowing control characters to bypass input validation. Additionally, BaseCookie.js_output() lacked the output validation applied to BaseCookie.output().

What

The fix for CVE-2026-0672, which rejected control characters in http.cookies.Morsel, was incomplete. The Morsel.update(), |= operator, and unpickling paths were not patched, allowing control characters to bypass input validation. Additionally, BaseCookie.js_output() lacked the output validation applied to BaseCookie.output().

Why

The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.

How

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

What

The fix for CVE-2026-0672, which rejected control characters in http.cookies.Morsel, was incomplete. The Morsel.update(), |= operator, and unpickling paths were not patched, allowing control characters to bypass input validation. Additionally, BaseCookie.js_output() lacked the output validation applied to BaseCookie.output().

Why

The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.

How

An attacker operating through a network path may attempt exploitation with low 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.
None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path
a network path → Improper Input Validation → cause the confidentiality, integrity or availability impact described by the vendor
Attack surface
Network
Privileges required
Low: a basic authenticated account 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-20 ↗

CWE-20: Improper Input Validation. The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.

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:L/UI:N/VC:L/VI:H/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.PRLowPrivileges required: The attacker needs basic user-level privileges.UINoneUser interaction: No action by another user is required.VCLowVulnerable-system confidentiality: A successful attack can cause a limited loss.VIHighVulnerable-system integrity: A successful attack can cause a major 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-20
A

Official authority intelligence

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

BSI · German · WID-SEC-2026-0741CPython: Mehrere Schwachstellen ermöglichen Manipulation von Dateien und DoS

Ein entfernter, authentisierter Angreifer kann mehrere Schwachstellen in CPython ausnutzen, um Dateien zu manipulieren oder um einen Denial-of-Service-Zustand herbeizuführen.

Official advisory ↗
CERT-FR · French · CERTFR-2026-AVI-0556Multiples vulnérabilités dans les produits VMware

cord?id=CVE-2026-3479 Référence CVE CVE-2026-3497 https://www.cve.org/CVERecord?id=CVE-2026-3497 Référence CVE CVE-2026-34986 https://www.cve.org/CVERecord?id=CVE-2026-34986 Référence CVE CVE-2026-35236 https://www.cve.org/CVERecord?id=CVE-2026-35236 Référence CVE CVE-2026-35237 https://www.cve.org/CVERecord?id=CVE-2026-35237 Référence CVE CVE-2026-35238 https://www.cve.org/CVERecord?id=CVE-2026-35238 Référence CVE CVE-2026-35239 https://www.cve.org/CVERecord?id=CVE-2026-35239 Référence CVE CVE-2026-35240 https://www.cve.org/CVERecord?id=CVE-2026-35240 Référence CVE CVE-2026-35469 https://www.cve.org/CVERecord?id=CVE-2026-35469 Référence CVE CVE-2026-3644 https://www.cve.org/CVERecord?id=CVE-2026-3644 Référence CVE CVE-2026-39883 https://www.cve.org/CVERecord?id=CVE-2026-39883 Référence CVE CVE-2026-39892 https://www.cve.org/CVERecord?id=CVE-2026-39892 Référence CVE CVE-2026-40192 https://www.cve.org/CVERecord?id=CVE-2026-40192 Référence CVE CVE-2026-41066 https://www.cve.org/CVERecord?id=CVE-2026-41066 Référence CVE CVE-2026-4111 https://www.cve.org/CVERecord?id=CVE-2026-4111 Référence CVE CVE-2026-4224 https://www.cve.org/CVERecord?id=CVE-2026-4224 Référence CVE CVE-2026-4424 https://www.cve.org/CVERecord?id=CVE-2026-4424 Référence CVE CVE-2026-4519 https://www.cve.org/CVERecord?id=CVE-2026

Official advisory ↗
CERT-FR · French · CERTFR-2026-AVI-0302Multiples vulnérabilités dans Python

De multiples vulnérabilités ont été découvertes dans Python. Elles permettent à un attaquant de provoquer un contournement de la politique de sécurité et un problème de sécurité non spécifié par l'éditeur.

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2026-018334Python Software FoundationのPythonにおける複数の脆弱性

http.cookies.Morsel内の制御文字を拒否する対策は不完全であり、Morsel.update()や|=演算子、およびアンピクル処理経路は修正されていませんでした。また、BaseCookie.js_output()には出力検証が欠けていました。これにより、入力検証を回避される可能性がありました。

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.
Fix availability varies by product
Affected
Fixed
Action
Use the product-specific evidence above. Patch only products with a verified fixed release, and keep every affected or under-investigation state without a matching fix in the remediation queue.
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 16 Mar 2026 · Last source change 13 Aug 2026, 00:27 UTC · CWE-20 · Improper Input Validation

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-2026-12484
Product sourceVendor CSAF · Red Hat Product Security
Remediation sourceVendor CSAF · Red Hat Product Security
CWE sourceCISA ADP
NVD statusNVD modified after enrichment

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

Material change intelligence

What changed after publication

View recent updates ↗
  1. Affected versionsThe structured affected or fixed version information changed.
    Before
    < 3.10.21; 3.11.0 < 3.11.16; 3.12.0 < 3.12.14; 3.13.0 < 3.13.13; 3.14.0 < 3.14.4; 3.15.0a1 < 3.15.0a8 · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
    After
    < 3.10.21; 3.11.0 < 3.11.16; 3.12.0 < 3.12.14; 3.13.0 < 3.13.13; 3.14.0 < 3.14.4; 3.15.0a1 < 3.15.0a8 · Fixed: For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258
    Red Hat Product Security ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release or patch reference recorded
Fixed release recorded from official guidance
ENISA EUVD · EUVD-2026-12484↗Red Hat Product Security security advisory↗Patch or update reference↗Patch or update reference↗Patch or update reference↗Patch or update reference↗CVE authority or vendor 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-2026-3644 · cve.blacktree.nl