CVE-2026-49855: tornadoweb tornado
Vulnerability summary
CVE-2026-49855 is a high (CVSS 7.5) vulnerability in tornadoweb tornado. EPSS estimates a 0.61% chance of exploitation in the next 30 days, higher than 48.2% of scored vulnerabilities.
Advisory lineage
Upstream 0 · Downstream 19 · Related 16Timeline
- 14-07-2026PublishedVulnerability first disclosed.
- 16-07-2026Last modifiedVulnerability information updated.
Description
Tornado is a Python web framework and asynchronous networking library. Prior to 6.5.6, Tornado gzip decompression routines processed limited-size chunks but did not enforce an overall limit on accumulated decompressed chunks, allowing a malicious server accessed by SimpleAsyncHTTPClient or an HTTPServer configured with decompress_request=True to consume effectively unlimited memory. This issue is fixed in version 6.5.6.
CVSS metrics
7 scores · 7 sources · 1 version- OSV · PypiEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · UbuntuEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · DebianEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · WolfiEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · ChainguardEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- NVDNIST7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS trend
Probability
0.61%
Chance of exploitation in the next 30 days
Percentile
48%
Versus all other CVEs
30-day change
+0.04 pp
From 0.57% on 20-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Chainguard2 products
- airflow-2All versions (No fix recorded)
- mitmproxy< 12.2.3-r1
Debian1 product
- python-tornadoAll versions (No fix recorded)
PyPI1 product
- tornado< 6.5.6
Tornadoweb1 product
- tornado< 6.5.6
Ubuntu1 product
- python-tornadoAll versions (No fix recorded)
Wolfi1 product
- mitmproxy< 12.2.3-r1
6 vendors · 7 products
References
11 links- github.com/tornadoweb/tornado/security/advisories/GHSA-mgf9-4vpg-hj56X Refsource CONFIRMWEBREPORTAdvisory
- github.com/tornadoweb/tornado/commit/ff808b33adc52d89a549376a5e3628e92abbc8ffX Refsource MISCREPORTFIX
- pypi.org/project/tornadoPACKAGE
