What is CVE-2021-22897?

CVE-2021-22897 is a medium-severity vulnerability in Haxx Curl, classified under CWE-840. CVSS score: 5.3/10. Published 2021-06-11.

How severe is CVE-2021-22897?

Medium severity. CVSS v3 base score is 5.3 out of 10.

Is CVE-2021-22897 known to be exploited?

3 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Vulnerability in Haxx Curl

CVE-2021-22897

curl 7.61.0 through 7.76.1 suffers from exposure of data element to wrong session due to a mistake in the code for CURLOPT_SSL_CIPHER_LIST when libcurl is built to use the Schannel TLS library. The selected cipher set was stored in a single "static" variable in the library, which has the surprising side-effect that if an application sets up multiple concurrent transfers, the last one that sets the ciphers will accidentally control the set used by all transfers. In a worst-case scenario, this weakens transport security significantly.

Published 2021-06-11 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N.

EPSS exploit prediction

EPSS: 0.030 (86.8th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 87th percentile — 86.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.030 · newest: 0.030 · change: 0.000

Affected products

Weakness classification (CWE)

Public proof-of-concept exploits

References

hackerone.com/reports/1172857 (Exploit, Third Party Advisory, Issue Tracking)
curl.se/docs/CVE-2021-22897.html (Patch, Vendor Advisory)
github.com/curl/curl/commit/bbb71507b7bab52002f9b1e0880bed6a32834511 (Patch, Third Party Advisory)
www.oracle.com//security-alerts/cpujul2021.html (Patch, Third Party Advisory)
www.oracle.com/security-alerts/cpujan2022.html (Patch, Third Party Advisory)
security.netapp.com/advisory/ntap-20210727-0007/ (Third Party Advisory)
www.oracle.com/security-alerts/cpuapr2022.html (Patch, Third Party Advisory)
cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf (Patch, Third Party Advisory)

Frequently asked questions

What is CVE-2021-22897?: CVE-2021-22897 is a medium-severity vulnerability in Haxx Curl, classified under CWE-840. CVSS score: 5.3/10. Published 2021-06-11.
How severe is CVE-2021-22897?: Medium severity. CVSS v3 base score is 5.3 out of 10.
Is CVE-2021-22897 known to be exploited?: 3 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.