CVE Intelligence
Low Injection

CVE-2026-103995 — Lenient parsing of integers for response body and chunk framing

Response body and chunk parsing would handle non-hex or negative integers incorrectly which could result in misinterpreting HTTP response contents.

Published Oct 27, 2026 · Updated Oct 28, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP, GitHub Security Advisories · CNA: PSF

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.
How the score was calculated
  • EPSS 0.4% (30-day exploitation probability)+4

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation
Not confirmed
Not in CISA KEV — an absence of record, not proof it is unexploited.
EPSS FIRST
0.36%
ahead of 30% of scored CVEs · Oct 29, 2026
Affects
Python
CPython
CVSS base
2.0
Low · 2 source(s)

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

  1. Identify exposed assets running the affected vendor/product/version combinations (Python CPython).
  2. No fix documented in the sources: reduce exposure and monitor the vendor advisory.
  3. Exploitation requires user interaction: tighten email/web filtering and warn affected users.
  4. Search available logs for exploit probes matching the vulnerability class (injection), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
Python CPython < 3.16.0 Vulnerable CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector
Network
Attack complexity
Low
Attack requirements
Present
Privileges required
High
User interaction
Passive
Scope
X
Confidentiality (vulnerable system)
None
Integrity (vulnerable system)
None
Availability (vulnerable system)
None
Confidentiality (subsequent)
None
Integrity (subsequent)
Low
Availability (subsequent)
None

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactScored by
2.0 CVSS 4.0 Low — — cna@python.org via NIST National Vulnerability Database
2.0 CVSS 4.0 Low — — PSF via CVE Program (cve.org) e CISA ADP
CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:P/VC:N/VI:N/VA:N/SC:N/SI:L/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 (score shown at the top: cna@python.org)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-444 · HTTP Request Smuggling

Other CVEs with this weakness →

EPSS over time FIRST

Oct 28, 2026 → Oct 29, 2026 · 2 reading(s) · max 0.36%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

  • Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
  • Look for parameters with command/query metacharacters and unexpected child processes of the service.
web/proxy/WAF logsnetwork IDS/IPSapplication logsendpoint telemetry (EDR)

Timeline

What happened to this CVE, newest first.

  • 2026
  • Source status changed · Received → Awaiting Analysis
    Oct 28, 2026 · NIST National Vulnerability Database
  • Affected products added · python software foundation/cpython
    Oct 27, 2026 · CVE Program (cve.org) e CISA ADP
  • Record published
    Oct 27, 2026
  • CVSS changed · 2.0
    Oct 27, 2026 · NIST National Vulnerability Database
  • Source status changed · → Received
    Oct 27, 2026 · NIST National Vulnerability Database
  • Record created in this database
    Oct 27, 2026 · Alertas do Telegram
  • CVE published
    Oct 27, 2026 · PSF

Source activity

Repeated readings are counted rather than listed.

  • 3× References added · Oct 27, 2026 – Oct 27, 2026
  • 1× Official description updated · Oct 27, 2026 – Oct 27, 2026

References

6 on the record

Elsewhere on this site

Python
every CVE for this vendor
Injection
same class
CWE-444
other pages naming this weakness

Related CVEs (same products)

  • CVE-2026-116566 socket.getaddrinfo() accepts embedded null bytes in host and port 12h
  • CVE-2026-115557 Distrust compromised intermediate certificates in ssl module 5d
  • CVE-2026-114583 tar filter allows writing outside destination via empty-named symlink 7d
  • CVE-2026-19553 SSLContext.wrap_bio() missing validation of server_hostname parameter 29d
  • CVE-2026-19445 Use-after-free of a server-side SSLContext when sni_callback switches contexts 29d
  • CVE-2026-12345 Race condition in tempfile.TemporaryDirectory cleanup allows deleting files outside the temporary directory Sep 29, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No fixed version, patch or mitigation documented.
  • No CISA SSVC assessment.
  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-103995 is "Lenient parsing of integers for response body and chunk framing", rated Low. It affects CPython (Python); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 2.0 describes technical severity. EPSS 0.36% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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