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CVE-2021-3737A flaw was found in python. An improperly handled HTTP response in the HTTP client code of python may allow a remote attacker, who…
- 7.5HighCVSS base score
- 13.2%Exploitation in 30 daysEPSS · top 3.6% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
A flaw was found in python. An improperly handled HTTP response in the HTTP client code of python may allow a remote attacker, who controls the HTTP server, to make the client script enter an infinite loop, consuming CPU time. The highest threat from this vulnerability is to system availability.
Timeline
ID reserved
By redhat
- 6 months later
· 6 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 |
|---|---|---|---|
| CISA-ADPADP (enrichment) | 3.1 | High7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| NVDNVD · Modified | 3.1 | High7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
- EPSS (exploitation in 30 days)
- 13.2% · top 3.6% of all CVEs (13 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: yes · Technical impact: partial
Loading the EPSS history…
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.5.
Affected products
python
- affected Fixed in python v3.6.14, python v3.7.11, python v3.8.11, python v3.9.6, python v3.10.0b2
References
References13
- https://bugs.python.org/issue44022 (opens in a new tab)x_transferred
- https://github.com/python/cpython/pull/25916 (opens in a new tab)x_transferred
- https://bugzilla.redhat.com/show_bug.cgi?id=1995162 (opens in a new tab)x_transferred
- https://github.com/python/cpython/pull/26503 (opens in a new tab)x_transferred
- https://ubuntu.com/security/CVE-2021-3737 (opens in a new tab)x_transferred
- https://www.oracle.com/security-alerts/cpujul2022.html (opens in a new tab)x_transferred
- https://python-security.readthedocs.io/vuln/urllib-100-continue-loop.html (opens in a new tab)x_transferred
- https://security.netapp.com/advisory/ntap-20220407-0009/ (opens in a new tab)x_transferred
- [debian-lts-announce] 20230524 [SECURITY] [DLA 3432-1] python2.7 security update (opens in a new tab)mailing-listx_transferred
- [debian-lts-announce] 20230630 [SECURITY] [DLA 3477-1] python3.7 security update (opens in a new tab)mailing-listx_transferred
- https://lists.debian.org/debian-lts-announce/2024/12/msg00000.html (opens in a new tab)
- https://lists.debian.org/debian-lts-announce/2024/11/msg00024.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-2021-27013 (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-2021-3737)Record last updated .