Apache Thrift: Decompression size limit bypass in Python TZlibTransport
Summary
The Python bindings of Apache Thrift (PyPI package thrift) contain a flaw in TZlibTransport, which stops enforcing its decompressed-size limit once the limit is exactly reached. An attacker who can send compressed Thrift data to a vulnerable Python service may be able to cause resource exhaustion and denial of service. The CVSS 4.0 base score is 8.2, but the vector only shows an availability impact and no confidentiality or integrity impact.
Affected
- Apache Thrift before 0.25.0 (Python bindings, PyPI package thrift)
- Linux distribution packages of thrift below 0.25.0-1 (for example Azure Linux, per vendor data)
- Debian 12 package builds: exact versions unknown, see Debian tracker
Fixed in
- Apache Thrift 0.25.0
- Azure Linux: 0.25.0-1 or later
- Debian and other distributions: check the distribution tracker, fixed versions not fully confirmed
Workaround
Unknown.
Exploitation
- CISA SSVC assessment: exploitation none, not automatable, partial technical impact.
- No public exploit code has been confirmed at this time (unverified, secondary source).
- Not listed in the CISA KEV catalog according to a secondary source (unverified).
Our recommendation
- Inventory Python applications and Linux packages that use the thrift library, including indirect dependencies.
- Upgrade to Apache Thrift 0.25.0 or the fixed build from your Linux distribution.
- Check that no application pins an older thrift version (for example below 0.25.0), as pins can block the fix.
- Prioritise internet-facing services that accept Thrift traffic.
- Note that 0.25.0 also covers the earlier issue CVE-2026-41608 (fixed in 0.24.0).
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- OSV: DEBIAN-CVE-2026-94636 osv.dev
- Vulners: CVE-2026-94636 vulners.com
- Strix: CVE-2026-94636 www.strix.ai
- Vulners: CBL-Mariner CBLMARINER:105410 vulners.com
- Apache mailing list thread (1rpq0d0g) lists.apache.org
- Apache mailing list thread (33otcgbq) lists.apache.org
- Databricks SQL Python PR 975 github.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 1 Nov 2026, 17:17.
Original description (NVD)
Improper handling of highly compressed data (data amplification), Function call with incorrectly specified arguments, Improper validation of specified quantity in input vulnerability in Apache Thrift py bindings. This issue affects Apache Thrift: before 0.25.0. Users are recommended to upgrade to version 0.25.0, which fixes the issue.
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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