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CVE Record

CVE-2023-27043: The email module of Python through 3.11.3 incorrectly parses e-mail addresses that contain a special charac...

The email module of Python through 3.11.3 incorrectly parses e-mail addresses that contain a special character. The wrong portion of an RFC2822 header is identified as the value of the addr-spec. In some applications, an attacker can bypass a protection mechanism in which application access is granted only after verifying receipt of e-mail to a specific domain (e.g., only @company.example.com addresses may be used for signup). This occurs in email/_parseaddr.py in recent versions of Python.

MediumCVSS 5.3Not KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

Python’s email parsing can misread crafted email addresses. If a business application uses that parsed result to decide whether someone belongs to an approved email domain, an outsider may bypass that control. This is most relevant to signup, tenant access, or invitation workflows that trust domain checks.

Executive priority

Treat as medium priority overall, but raise urgency for customer portals, employee-only signup, partner onboarding, or multi-tenant access controls using email-domain verification. Patch during normal maintenance unless those workflows depend on vulnerable parsing.

Technical view

CVE-2023-27043 affects Python email parsing through 3.11.3 in email/_parseaddr.py. Special characters in RFC2822 headers can cause the wrong portion to be treated as the addr-spec. CVSS is 5.3, with low integrity impact. The issue maps to input validation and parser inconsistency weaknesses.

Likely exposure

Exposure is application-specific. Risk exists where Python applications parse user-supplied email addresses and use the parsed domain for access decisions, allowlists, signup restrictions, or invitation eligibility. Systems merely sending email or not enforcing domain-based authorization are less likely to be impacted.

Exploitation context

The source bundle does not show KEV listing or confirmed active exploitation. Exploitation would require an application workflow that accepts crafted email address input and trusts Python’s parsed address for a security decision. The main business impact is unauthorized access or account creation, not system takeover.

Researcher notes

The CVE description names Python through 3.11.3 and email/_parseaddr.py, but the bundle does not provide a single definitive fixed upstream version. Fedora advisories indicate downstream updates. Avoid assuming broad impact; confirm whether application security decisions rely on parsed addr-spec values.

Mitigation direction

  • Inventory Python runtimes and packages at or below 3.11.3.
  • Apply Python, operating system, or vendor updates referenced by your platform vendor.
  • Review domain allowlist logic; do not trust parser output alone for authorization.
  • Require verified mailbox ownership and canonical domain checks before granting access.
  • Check NetApp, Fedora, and other vendor advisories for product-specific guidance.

Validation and detection

  • Find code using Python email parsing for login, signup, invitations, or domain allowlists.
  • Confirm runtime versions and distro package backport status with vendor advisories.
  • Review tests for malformed or ambiguous email address handling.
  • Verify access decisions depend on confirmed mailbox ownership, not only parsed strings.
  • Document affected applications and residual controls for vulnerability management tracking.
Prepared
Confidence
medium
Sources
6

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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cwe · low confidence lookup

CWE-1286: Exact CWE lookup

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cwe · low confidence lookup

CWE-20: Exact CWE lookup

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cve · low confidence lookup

CVE-2023-27043 mapping review

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Vulnerability profileCVE Program record
Severity
Medium
CVSS
5.3 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
3Timeline events
3ADP providers
43Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: pocAutomatable: yesTechnical Impact: partial

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
5.3CVSS 3.1MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N3.91.4CISA-ADP

Vulnerability scoring details

Base CVSS 3.1 score

5.3Medium
CVSS 3.1 vector shape for CVE-2023-27043Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CVECVE Program Container
CISA-ADPCISA ADP Vulnrichment
cvssV3_1other:ssvc
siemens-SADPADP container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

CWE-1286CWE-20

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-1286 · source CWE mapping

Improper Validation of Syntactic Correctness of Input

Improper Validation of Syntactic Correctness of Input represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs
CWE-20 · source CWE mapping

Improper Input Validation

Improper Input Validation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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