CVE-2021-22901curl 7.75.0 through 7.76.1 suffers from a use-after-free vulnerability resulting in already freed memory being used when a TLS 1.3 session…
- 8.1HighCVSS base score
- 63.5%Exploitation in 30 daysEPSS · top 0.8% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
curl 7.75.0 through 7.76.1 suffers from a use-after-free vulnerability resulting in already freed memory being used when a TLS 1.3 session ticket arrives over a connection. A malicious server can use this in rare unfortunate circumstances to potentially reach remote code execution in the client. When libcurl at run-time sets up support for TLS 1.3 session tickets on a connection using OpenSSL, it stores pointers to the transfer in-memory object for later retrieval when a session ticket arrives. If the connection is used by multiple transfers (like with a reused HTTP/1.1 connection or multiplexed HTTP/2 connection) that first transfer object might be freed before the new session is established on that connection and then the function will access a memory buffer that might be freed. When using that memory, libcurl might even call a function pointer in the object, making it possible for a remote code execution if the server could somehow manage to get crafted memory content into the correct place in memory.
Timeline
ID reserved
By hackerone
- 5 months later
· 5 months later
Published
- 5 years later
· 5 years later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| NVDNVD · Modified | 3.1 | High8.1 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H |
- EPSS (exploitation in 30 days)
- 63.5% · top 0.8% of all CVEs (15 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: yes · Technical impact: total
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 8.1.
Affected products
https://github.com/curl/curl
- affected 7.75.0 through 7.76.1
References
References13
- https://hackerone.com/reports/1180380 (opens in a new tab)x_refsource_MISCx_transferred
- https://curl.se/docs/CVE-2021-22901.html (opens in a new tab)x_refsource_MISCx_transferred
- https://github.com/curl/curl/commit/7f4a9a9b2a49547eae24d2e19bc5c346e9026479 (opens in a new tab)x_refsource_MISCx_transferred
- https://www.oracle.com//security-alerts/cpujul2021.html (opens in a new tab)x_refsource_MISCx_transferred
- https://security.netapp.com/advisory/ntap-20210723-0001/ (opens in a new tab)x_refsource_CONFIRMx_transferred
- https://www.oracle.com/security-alerts/cpujan2022.html (opens in a new tab)x_refsource_MISCx_transferred
- https://security.netapp.com/advisory/ntap-20210727-0007/ (opens in a new tab)x_refsource_CONFIRMx_transferred
- https://www.oracle.com/security-alerts/cpuapr2022.html (opens in a new tab)x_refsource_MISCx_transferred
- https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf (opens in a new tab)x_refsource_CONFIRMx_transferred
- https://cert-portal.siemens.com/productcert/pdf/ssa-732250.pdf (opens in a new tab)x_refsource_CONFIRMx_transferred
- https://cert-portal.siemens.com/productcert/html/ssa-389290.html (opens in a new tab)
- https://cert-portal.siemens.com/productcert/html/ssa-732250.html (opens in a new tab)
- https://cert-portal.siemens.com/productcert/html/ssa-398330.html (opens in a new tab)
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2021-10033 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2021-22901)Record last updated .