Affects CPython's ssl module used widely across services and apps; allows TLS trust bypass/MITM, so it's broadly impactful and newsworthy.
CVE-2026-115557
Python ssl accepted compromised certificates enabling TLS MITM; denylist added to block them.
Is CVE-2026-115557 being exploited?
Not confirmed. CVE-2026-115557 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.53% probability of exploitation in the next 30 days.
How severe is CVE-2026-115557?
CVE-2026-115557 is rated Critical with a CVSS score of 9.4. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-115557?
Yes. A fix has been recorded for CVE-2026-115557. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-115557 affect?
CVE-2026-115557 affects CPython ssl module, Python interpreters prior to patched commits, Applications using Python's TLS/ssl. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-115557?
Upgrade Python to the patched release, rebuild deployments, and rotate any exposed certs/keys.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Accepting known-compromised certs enables TLS MITM, data/credential theft, token interception and potential code/supply-chain tampering.
Immediate action required
- affected< 3.16.0
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.