CVE-2026-41608: Apache Thrift: Unbounded Zlib Decompression in Python THeaderTransport

CVE-2026-41608 is a vulnerability in Apache Thrift: Unbounded Zlib Decompression in Python THeaderTransport, rated Moderate by Microsoft, with a CVSS 3.1 base score of 7.5 (High). An attacker can exploit it remotely over the network, without any privileges and without user interaction. Microsoft has not reported exploitation in the wild. The EPSS model estimates a 1.03% probability of exploitation activity in the next 30 days, higher than 64% of all scored vulnerabilities. Microsoft released the fix on 6 August 2026, outside Patch Tuesday. It affects 1 product in 1 product family (Open Source Software).

Key facts

CVE ID

CVE-2026-41608

Severity

High CVSS 7.5

Microsoft severity

Moderate

Exploited in the wild

No

Publicly disclosed

No

Weakness

CWE-409

EPSS

1.03% (percentile 64%)

CISA KEV

Not listed

Released

6 August 2026

Last updated

6 August 2026

Patch Tuesday

July 2026 Patch Tuesday

Product families

Open Source Software

CVSS score and vector

Microsoft scores CVE-2026-41608 at 7.5 (temporal 6.9) using CVSS 3.1. Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U

Affected products (1)

Open Source Software

NIST NVD data

NVD status

Modified

NVD CVSS

7.5 (HIGH)

NVD weakness

CWE-409

Published to NVD

27 July 2026

NVD last modified

24 October 2026

Affected configurations (CPE)

References

• https://lists.apache.org/thread/7v3jhgwfbmhx42424phydlnzb109g8b9 (Release Notes)
• https://lists.apache.org/thread/vwsbcwqdpwdtp8qkjo11ol6rodbfm21f (Vendor Advisory)
• http://www.openwall.com/lists/oss-security/2026/07/24/32 (Mailing List, Third Party Advisory)

Revision history

Related vulnerabilities

More from the July 2026 Patch Tuesday

• CVE-2026-57968: Windows Subsystem for Linux (WSL2) Kernel Elevation of Privilege Vulnerability (High, CVSS 7.8)
• CVE-2026-57973: Windows Subsystem for Linux (WSL2) Kernel Tampering Vulnerability (Medium, CVSS 6.3)
• CVE-2026-44210: Kata Containers have VM Escape via virtiofsd Argument Injection through Default-Enabled Pod Annotations (Critical, CVSS 9.9)
• CVE-2026-15043: DBI::SQL::Nano versions from 1.42 before 1.651 for Perl have inverted <= and >= SQL operators on text (Critical, CVSS 9.8)
• CVE-2026-17543: SQL injection in ext-pgsql via E'...' backslash breakout (Critical, CVSS 9.8)
• CVE-2026-38968: ntopng through 6.6 is vulnerable to Predictable Session Identifier which can lead to Session Hijacking. HTTP session identifiers in src/HTTPserver.cpp use weak time-seeded pseudo-randomness during session creation. As a result, fresh authenticated logins can receive deterministic or colliding session cookies under attacker-controlled timing. (Critical, CVSS 9.8)
• CVE-2026-53374: drm/amdgpu: zero-initialize GART table on allocation (Critical, CVSS 9.8)
• CVE-2026-53376: drm/amdkfd: Add upper bound check for num_of_nodes (Critical, CVSS 9.8)
• CVE-2026-53384: serial: 8250_dw: unregister 8250 port if clk_notifier_register() fails (Critical, CVSS 9.8)
• CVE-2026-53403: fbdev: Fix fb_new_modelist to prevent null-ptr-deref in fb_videomode_to_var (Critical, CVSS 9.8)
• CVE-2026-55971: Apache Thrift: C++ ZLIB heap buffer overflow (write) in THeaderTransport::untransform() (Critical, CVSS 9.8)
• CVE-2026-57433: Storable versions before 3.41 for Perl have a signed integer overflow when deserializing a crafted SX_HOOK record (Critical, CVSS 9.8)

All vulnerabilities of this release: July 2026 Patch Tuesday · July 2026 briefing

Sources

• Microsoft Security Update Guide: CVE-2026-41608
• NIST NVD: CVE-2026-41608
• CVE.org record: CVE-2026-41608