6.5

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

Modified
AliasesSUSE-SU-2022:2047-1UBUNTU-CVE-2021-43797DEBIAN-CVE-2021-43797
Published 09-12-2021Last modified 08-10-2026

Vulnerability summary

CVE-2021-43797 is a medium (CVSS 6.5) vulnerability in debian debian_linux. EPSS estimates a 2.88% chance of exploitation in the next 30 days, higher than 86.8% of scored vulnerabilities.

Priority
Routine

Not severe (CVSS 6.5, network access); no exploitation reported by the 5 checked sources

Source freshness unavailable

How is this decided?
CVSS score
6.5/10
010
Medium · v3.1 (CVE.org)
EPSS score
2.88%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 12 · Related 5
DLA-3268-1DSA-5316-1RHSA-2022:4918RHSA-2022:4919RHSA-2022:5498RHSA-2022:6782

Timeline

  1. 09-12-2021
    PublishedVulnerability first disclosed.
  2. 08-10-2026
    Last modifiedVulnerability information updated.

Description

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.

CVSS metrics

8 scores · 7 sources · 2 versions

EPSS trend

Probability

2.88%

Chance of exploitation in the next 30 days

Percentile

87%

Versus all other CVEs

30-day change

No change 0.00 pp

From 2.88% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: network-reachable, no authentication, user interaction (CVSS vector). Other conditions: not stated in public data.

Oracle13 products
Chainguard4 products
  • druidAll versions (No fix recorded)
  • hadoop-fips-3.3.6All versions (No fix recorded)
  • hadoop-fips-3.4.2All versions (No fix recorded)
  • hadoop-fips-3.5All versions (No fix recorded)
Opensuse4 products
  • netty3&distro=openSUSE Leap 15.3< 3.10.6-150200.3.3.2
  • netty3&distro=openSUSE Leap 15.4< 3.10.6-150200.3.3.2
  • netty3&distro=openSUSE Tumbleweed< 3.10.6-9.1
  • netty&distro=openSUSE Tumbleweed< 4.1.72-1.1
Debian2 products
Io.netty2 products
  • nettyAll versions (No fix recorded)
  • netty-codec-http≥ 4.0.0, < 4.1.71.Final
Netapp2 products
Suse2 products
  • netty3&distro=SUSE Linux Enterprise Module for Development Tools 15 SP3< 3.10.6-150200.3.3.2
  • netty3&distro=SUSE Linux Enterprise Module for Development Tools 15 SP4< 3.10.6-150200.3.3.2
Netty1 product
  • netty≤ 4.1.7.0.Final | < 4.1.71
Org.jboss.netty1 product
  • nettyAll versions (No fix recorded)
Quarkus1 product
Ubuntu1 product
  • nettyAll versions (No fix recorded) | < 1:4.0.34-1ubuntu0.1~esm1 | < 1:4.1.7-4ubuntu0.1+esm2 | < 1:4.1.45-1ubuntu0.1~esm1 | < 1:4.1.48-4+deb11u1build0.22.04.1
Wolfi1 product
  • druidAll versions (No fix recorded)

12 vendors · 34 products

References

19 links
Show all 19 references