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Fencer Vulns
medium 4.3

CVE-2021-22890 json

curl 7.63.0 to and including 7.75.0 includes vulnerability that allows a malicious HTTPS proxy to...

published 2021-04-01 5 y ago modified 2026-10-14 26 d ago also EUVD-2021-10022 , JLSEC-2025-27

cvss
4.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
3.1%
EPSS 3.1% chance of exploitation in 30 days, percentile 87%
public exploits
0
none known

Summary

curl 7.63.0 to and including 7.75.0 includes vulnerability that allows a malicious HTTPS proxy to MITM a connection due to bad handling of TLS 1.3 session tickets. When using a HTTPS proxy and TLS 1.3, libcurl can confuse session tickets arriving from the HTTPS proxy but work as if they arrived from the remote server and then wrongly "short-cut" the host handshake. When confusing the tickets, a HTTPS proxy can trick libcurl to use the wrong session ticket resume for the host and thereby circumvent the server TLS certificate check and make a MITM attack to be possible to perform unnoticed. Note that such a malicious HTTPS proxy needs to provide a certificate that curl will accept for the MITMed server for an attack to work - unless curl has been told to ignore the server certificate check.

Patch / fix

  • julia LibCURL_jll 7.81.0+0
  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP V3.1.5
  • Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP V3.1.5
  • Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP V3.1.5
  • curl Debian 14, Debian 13, Debian 12 7.74.0-1.2

debian advisories DEBIAN-CVE-2021-22890

  • curl Ubuntu 20.04 LTS 7.68.0-1ubuntu2.5

ubuntu advisories UBUNTU-CVE-2021-22890

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • jbcs-httpd24 jboss core services 1 1-18.jbcs.el7
  • jbcs-httpd24 jboss core services 1 1-18.el8jbcs
  • jbcs-httpd24-apr jboss core services 1 1.6.3-105.jbcs.el7
  • jbcs-httpd24-apr jboss core services 1 1.6.3-105.el8jbcs
  • jbcs-httpd24-curl jboss core services 1 7.77.0-2.jbcs.el7
  • jbcs-httpd24-curl jboss core services 1 7.77.0-2.el8jbcs
  • jbcs-httpd24-httpd jboss core services 1 2.4.37-74.jbcs.el7
  • jbcs-httpd24-httpd jboss core services 1 2.4.37-74.el8jbcs

red hat advisories RHSA-2021:2472

  • curl SLE Module for Basesystem 15 SP2, SLE Micro 5.0 7.66.0-4.14.1

suse advisories SUSE-SU-2021:1006-1

  • curl openSUSE Tumbleweed 7.79.1-1.1
  • curl openSUSE Leap 15.2 7.66.0-lp152.3.15.1
  • curl-mini openSUSE Leap 15.2 7.66.0-lp152.3.15.1

opensuse advisories openSUSE-SU-2024:10582-1openSUSE-SU-2021:0510-1

  • curl Alpine 3.24, Alpine 3.23, Alpine 3.22 +10 more 7.76.0-r0

alpine advisories ALPINE-CVE-2021-22890

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • curl Arch Linux 7.76.0-1
  • lib32-curl Arch Linux 7.76.0-1
  • libcurl-compat Arch Linux 7.76.0-1
  • lib32-libcurl-compat Arch Linux 7.76.0-1

arch linux advisories AVG-1753AVG-1754AVG-1755AVG-1756

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-22890 updated cvss 3.7

curl: TLS 1.3 session ticket mix-up with HTTPS proxy host

  • Red Hat Ceph Storage 2 curl, libcurl
    affected: no fix planned “Out of support scope”
  • Red Hat JBoss Core Services Apache HTTP Server 2.4.37 SP8
    fixed: vendor fix RHSA-2021:2471
  • Red Hat JBoss Core Services on RHEL 7 Server jbcs-httpd24 1-18.jbcs.el7, jbcs-httpd24-runtime 1-18.jbcs.el7, jbcs-httpd24-apr 1.6.3-105.jbcs.el7, jbcs-httpd24-curl 7.77.0-2.jbcs.el7, jbcs-httpd24-httpd 2.4.37-74.jbcs.el7, jbcs-httpd24-jansson 2.11-55.jbcs.el7, +23 more Red Hat JBoss Core Services on RHEL 8 jbcs-httpd24 1-18.el8jbcs, jbcs-httpd24-runtime 1-18.el8jbcs, jbcs-httpd24-apr 1.6.3-105.el8jbcs, jbcs-httpd24-curl 7.77.0-2.el8jbcs, jbcs-httpd24-brotli 1.0.6-40.el8jbcs, jbcs-httpd24-httpd 2.4.37-74.el8jbcs, +30 more
    fixed: vendor fix RHSA-2021:2472
  • Red Hat .NET Core 2.1 on Red Hat Enterprise Linux rh-dotnet21-curl, rh-dotnet21-libcurl Red Hat .NET Core 3.1 on Red Hat Enterprise Linux rh-dotnet31-curl, rh-dotnet31-libcurl Red Hat Enterprise Linux 6 curl, libcurl Red Hat Enterprise Linux 7 curl, libcurl Red Hat Enterprise Linux 8 curl, libcurl, libcurl-minimal Red Hat Enterprise Linux 9 curl, libcurl, curl-minimal, libcurl-minimal
    +1 more products
    Red Hat Software Collections httpd24-curl, httpd24-libcurl
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

cisa ICSA-23-348-10 updated cvss 3.7

Siemens SIMATIC S7-1500

  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) >= 3.1.0, < 3.1.5 Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) >= 3.1.0, < 3.1.5 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) >= 3.1.0, < 3.1.5 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0) >= 3.1.0, < 3.1.5 Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0) >= 3.1.0, < 3.1.5
    affected: fixed in V3.1.5, mitigation support.industry.siemens.com

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
17 mo ago

Exploit prediction

3.06% chance of exploitation in the next 30 days, higher than 87% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • hackerone.com https://hackerone.com/reports/1129529 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CISA ADP 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
NVD 3.1 3.7 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
CNA 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
NVD 2.0 4.3 AV:N/AC:M/Au:N/C:N/I:P/A:N
OSV 3.1 3.7 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

Affected packages

ecosystem package affected fixed in
julia LibCURL_jll
<7.81.0+0
7.81.0+0

Affected products

  • n/a https://github.com/curl/curl
  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP
  • Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP
  • Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP

Classification

Weakness
  • CWE-300 Channel Accessible by Non-Endpoint
  • CWE-290 Authentication Bypass by Spoofing

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.