CVE-2021-43797: HTTP fails to validate against control chars in header names which may lead to HTTP request smuggling
Telemetry drift only. No threshold crossed and no authority ruling changed.
CVE record, CISA KEV and EPSS as of 2026-10-18.
CVEs like this one computed, by meaning
What to do now held facts and links
- Upgrade to the fixed version for your release line, or later: netty 4.1.71; quarkus 2.5.3 upper bounds of the CVE record's affected ranges
- Later advisories still cover the fixes above and name higher ones: netty-codec-http 4.1.77.Final (CVE-2022-24823), 4.1.108.Final (CVE-2024-29025), 4.1.125.Final (CVE-2025-58056), 4.1.129.Final (CVE-2025-67735), 4.1.132.Final (CVE-2026-33870), 4.1.133.Final (CVE-2026-41417), 4.1.133.Final (CVE-2026-42580), 4.1.133.Final (CVE-2026-42581), 4.1.133.Final (CVE-2026-42584), 4.1.133.Final (CVE-2026-42585), 4.1.133.Final (CVE-2026-42587), 4.1.135.Final (CVE-2026-50020), 4.1.136.Final (CVE-2026-55831), 4.1.136.Final (CVE-2026-55833), 4.1.136.Final (CVE-2026-56745), 4.1.136.Final (CVE-2026-56746), 4.1.136.Final (CVE-2026-59898), 4.1.136.Final (CVE-2026-59899), 4.1.136.Final (CVE-2026-59921), 4.1.137.Final (CVE-2026-59903) OSV advisories
- Record your decision, dated and frozen with today's evidence: patch by a date · mitigated by a compensating control · deferred · accepted the risk · not affected
- Check your version against the ranges this record publishes.
What it is stated by the CNA
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.
- weakness
- CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request Smuggling')
- affected
- netty
- published ranges
- netty < 4.1.71; quarkus < 2.5.3; oracle banking deposits and lines of credit servicing 2.7; oracle banking party management 2.7.0; and 16 more on the CVE page
- first unaffected version, by branch
- netty 4.1.71; quarkus 2.5.3
- fixed by package (from OSV advisories)
- io.netty:netty-codec-http (Maven): 4.1.71.Final GHSA-wx5j-54mm-rqqq
- later fixes (from OSV advisories)
- netty-codec-http 4.1.71.Final is inside a range CVE-2022-24823 (GHSA-269q-hmxg-m83q) lists as affected. That advisory is fixed in 4.1.77.Final.netty-codec-http 4.1.71.Final is inside a range CVE-2024-29025 (GHSA-5jpm-x58v-624v) lists as affected. That advisory is fixed in 4.1.108.Final.netty-codec-http 4.1.71.Final is inside a range CVE-2025-58056 (GHSA-fghv-69vj-qj49) lists as affected. That advisory is fixed in 4.1.125.Final.netty-codec-http 4.1.71.Final is inside a range CVE-2025-67735 (GHSA-84h7-rjj3-6jx4) lists as affected. That advisory is fixed in 4.1.129.Final.netty-codec-http 4.1.71.Final is inside a range CVE-2026-33870 (GHSA-pwqr-wmgm-9rr8) lists as affected. That advisory is fixed in 4.1.132.Final.netty-codec-http 4.1.71.Final is inside a range CVE-2026-41417 (GHSA-v8h7-rr48-vmmv) lists as affected. That advisory is fixed in 4.1.133.Final.
- severity
- 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
- assigned by
- GitHub_M
- published
- 2021-12-09
check us github.com github.com oracle.com security.netapp.com
Exploit code held, dated
- exploit code
- None held in the PoC-in-GitHub feed. A public repository changes this brief.
What moved held, dated
| date | EPSS | event |
|---|---|---|
| 10 Dec 2021 | 0.00624 | |
| 6 Jan 2022 | 0.02742 | |
| 7 Jan 2022 | 0.0363 | |
| 4 Feb 2022 | 0.03283 | |
| 7 Mar 2023 | 0.00101 | scoring model v2023.03.01 |
| 17 Mar 2025 | 0.00123 | scoring model v2025.03.14 |
| 1 Mar 2026 | 0.00212 | |
| 4 Mar 2026 | 0.00381 | |
| 15 Jun 2026 | 0.02682 | scoring model v2026.06.15 |
| 2 Oct 2026 | 0.02884 |
57 observations held. A step marked with a scoring model moved because the measurement was replaced, not because the vulnerability changed.
Outside the record researched, cited
This section reads the record's references and adds cited findings from outside it. It needs an account. Everything above is held facts and is complete without it.
What would change this brief held, dated
- CISA KEV
- Not listed in the catalogue we hold. A listing changes this brief.
- exploit probability
- 0.03 on 2026-10-02 (FIRST's EPSS, a probability and not evidence of exploitation). Next band line: 10% (0.10). Crossing a line changes this brief.
- fix
- Held: netty 4.1.71; quarkus 2.5.3. A newer fix from the CNA or OSV changes this brief.
How to check this
Every value above is held with two dates: when it was true upstream (as_of) and when we recorded it (tx_from). Re-derive the exploit probability as it stood on any date:
SELECT value, source, source_version, as_of, tx_from
FROM volatile_valid_as_of('CVE-2021-43797', '2026-10-30T23:59:59.999999Z', now());