CVE Intelligence
Medium Injection

CVE-2021-43797 — HTTP fails to validate against control chars in header names which may lead to HTTP request smuggling

Netty is an asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers & clients. Netty prior to version 4.1.71.Final skips control chars when they are present at the beginning / end of the header name. It should instead fail fast as these are not allowed by the spec and could lead to HTTP request smuggling. Failing to do the validation might cause netty to "sanitize" header names before it forward these to another remote system when used as proxy. This remote system can't see the invalid usage anymore, and therefore does not do the validation itself. Users should upgrade to version 4.1.71.Final.

Published Dec 9, 2021 · Updated Oct 13, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: GitHub_M

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 2.9% (30-day exploitation probability)+13
  • Technical severity (medium)+3

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
2.88%
ahead of 87% of scored CVEs · Oct 14, 2026
Affects
Debian
Debian Linux and 17 more
CVSS base
6.5
Medium · 3 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation
None
none · proof-of-concept · active
Automatable
No
can an attacker script the kill-chain steps
Technical impact
Partial
partial · total control of the vulnerable component

Remediation

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

  • Documented patch — github.com (NIST National Vulnerability Database)
  • Documented patch — www.oracle.com (NIST National Vulnerability Database)
  • Documented patch — www.oracle.com (NIST National Vulnerability Database)

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 (Debian Debian Linux, Netapp Oncommand Workflow Automation, Netapp Snapcenter…).
  2. The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
  3. Apply the fixed version or the patch documented under Remediation.
  4. Exploitation requires user interaction: tighten email/web filtering and warn affected users.
  5. 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
Debian Debian Linux version 11.0version 10.0 Vulnerable NIST National Vulnerability Database
Netapp Oncommand Workflow Automation versions not specified by the source Vulnerable NIST National Vulnerability Database
Netapp Snapcenter versions not specified by the source Vulnerable NIST National Vulnerability Database
Netty Netty < 4.1.71 Vulnerable NIST National Vulnerability Database
Netty Netty version <= 4.1.7.0.Final Vulnerable CVE Program (cve.org) e CISA ADP
Oracle Banking Deposits And Lines Of Credit Servicing version 2.7 Vulnerable NIST National Vulnerability Database
Oracle Banking Party Management version 2.7.0 Vulnerable NIST National Vulnerability Database
Oracle Banking Platform version 2.6.2 Vulnerable NIST National Vulnerability Database
Oracle Coherence version 14.1.1.0.0version 12.2.1.4.0 Vulnerable NIST National Vulnerability Database
Oracle Communications Cloud Native Core Binding Support Function version 1.11.0 Vulnerable NIST National Vulnerability Database
Oracle Communications Cloud Native Core Network Slice Selection Function version 1.8.0 Vulnerable NIST National Vulnerability Database
Oracle Communications Cloud Native Core Policy version 1.15.0 Vulnerable NIST National Vulnerability Database
Oracle Communications Cloud Native Core Security Edge Protection Proxy version 1.7.0 Vulnerable NIST National Vulnerability Database
Oracle Communications Cloud Native Core Unified Data Repository version 1.15.0 Vulnerable NIST National Vulnerability Database
Oracle Communications Design Studio version 7.4.2 Vulnerable NIST National Vulnerability Database
Oracle Communications Instant Messaging Server version 8.1 Vulnerable NIST National Vulnerability Database
Oracle Helidon version 1.4.10version 2.4.0 Vulnerable NIST National Vulnerability Database
Oracle Peoplesoft Enterprise Peopletools version 8.59version 8.58 Vulnerable NIST National Vulnerability Database
Quarkus Quarkus < 2.5.3 Vulnerable NIST National Vulnerability Database

Attack characteristics

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

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

Every base score collected

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

ScoreVersionSeverityExpl.ImpactScored by
6.5 CVSS 3.1 Medium 2.8 3.6 security-advisories@github.com via NIST National Vulnerability Database
6.5 CVSS 3.1 Medium 2.8 3.6 nvd@nist.gov via NIST National Vulnerability Database
6.5 CVSS 3.1 Medium — — GitHub_M via CVE Program (cve.org) e CISA ADP
4.3 CVSS 2.0 Medium 8.6 2.9 nvd@nist.gov via NIST National Vulnerability Database
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N (score shown at the top: nvd@nist.gov)

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 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 2.88%

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
  • Affected products added · netty/netty
    Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
  • SSVC assessment updated
    Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
  • Record published
    Oct 13, 2026
  • Fix documented
    Oct 13, 2026 · NIST National Vulnerability Database
  • CVSS changed · 6.5
    Oct 13, 2026 · NIST National Vulnerability Database
  • Source status changed · → Modified
    Oct 13, 2026 · NIST National Vulnerability Database
  • Record created in this database
    Oct 13, 2026 · NIST National Vulnerability Database
  • 2021
  • CVE published
    Dec 9, 2021 · GitHub_M

Source activity

Repeated readings are counted rather than listed.

  • 1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

7 on the record

Elsewhere on this site

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

Related CVEs (same products)

  • CVE-2026-100665 Netty 4.2.11 through 4.2.17 QUIC Hostname Verification Bypass 19d
  • CVE-2026-100662 Netty HTTP/3 QPACK encoder-stream unbounded memory exhaustion DoS 19d
  • CVE-2026-100663 Netty HTTP/1 CONNECT authority-form mistranslated to malformed HTTP/3 19d
  • CVE-2026-100664 Netty 4.2.2 through 4.2.17 HTTP/1 Host Header Authority Confusion 19d
  • CVE-2026-100661 Netty HTTP/3 QPACK Prefixed Integer DoS via Unbounded Accumulation 19d
  • CVE-2026-100666 Netty 4.2.0 through 4.2.16 Response Desynchronization via HttpServerCodec 19d

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 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-2021-43797 is "HTTP fails to validate against control chars in header names which may lead to HTTP request smuggling", rated Medium. It affects Debian Linux (Debian); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 6.5 describes technical severity. EPSS 2.88% 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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