CVSS 4.0
6.3 mediumCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:NCVE-2026-115559 python software foundation cpython
Medium (6.3) in python software foundation cpython. EPSS 0.3% estimated probability of exploitation activity in the next 30 days.
On this page
IMAP4.starttls() wraps the socket in TLS but leaves self._readbuf, imaplib's own read-ahead buffer, untouched. Any plaintext bytes that arrived in the same recv() as the tagged OK to STARTTLS are returned by readline() after the handshake, so the client treats them as the first responses on the protected channel. A network attacker who cannot break TLS can append forged lines after the server's OK, let the handshake complete with the real server and a valid certificate, and have the client accept the forged CAPABILITY and the forged tagged completion of the next command. This is the STARTTLS command/response injection class of CVE-2011-0411.
Severity
- EPSS
- 0.3% estimated probability of exploitation activity in the next 30 days; 21st percentile. Scored 2026-11-13. A forecast for this CVE across the internet, not for your own systems.
- Published
- Modified
- Assigned by
- PSF (CNA)
- NVD analysis
- Awaiting analysis
- Record from
- the NVD, synced
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Affected
- python software foundation:cpython
Versions
From the CNA's record in the CVE List.
| Product | Affected |
|---|---|
| Python Software Foundation CPython | before 3.16.0 |
Linux distributions
| Distribution | Release | Package | Fixed in | Advisory |
|---|---|---|---|---|
| Ubuntu | 22.04:LTS | python3.10 | no fix listed | UBUNTU-CVE-2026-115559 |
| Ubuntu | 24.04:LTS | python3.12 | no fix listed | UBUNTU-CVE-2026-115559 |
| Ubuntu | 26.04:LTS, 26.10 | python3.14 | no fix listed | UBUNTU-CVE-2026-115559 |
| Ubuntu | Pro:14.04:LTS | python2.7, python3.4, python3.5 | no fix listed | UBUNTU-CVE-2026-115559 |
| Ubuntu | Pro:16.04:LTS | python2.7, python3.5 | no fix listed | UBUNTU-CVE-2026-115559 |
| Ubuntu | Pro:18.04:LTS | python2.7, python3.6, python3.7 and 1 more | no fix listed | UBUNTU-CVE-2026-115559 |
| Ubuntu | Pro:20.04:LTS | python2.7, python3.8, python3.9 | no fix listed | UBUNTU-CVE-2026-115559 |
| Ubuntu | Pro:22.04:LTS | python2.7, python3.11 | no fix listed | UBUNTU-CVE-2026-115559 |
| Azure Linux | 3 | python-py | no fix listed | AZL-113323 |
| Azure Linux | 3 | python3 | no fix listed | AZL-113329 |
From the distributions' data via OSV.dev: Ubuntu Security Notices © Canonical Ltd., CC BY-SA 4.0; Microsoft's Azure Linux vulnerability data, MIT. Modified: reformatted and linked to CVE records. Credits. On the distributions' own pages: Ubuntu.