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CPython fixed a medium-severity Server-Side Request Forgery issue in Lib/ftplib.py tracked as CVE-2026-8328, after maintainers found that ftplib.ftpcp() still trusted a source FTP server’s self-reported PASV IPv4 address. The flaw persisted because ftpcp() had not been updated during the earlier CVE-2021-4189 remediation and continued to call parse227() directly, allowing an attacker-controlled FTP server to influence the host and port used for the target server’s data connection.
The patch changes ftpcp() to use the source server’s actual peer address and to honor the existing trust_server_pasv_ipv4_address opt-out, bringing its behavior in line with FTP.makepasv(). Python linked the issue to advisory GHSA-w8c5-q2xf-gf7c; the fix was merged into the main branch and backported to multiple maintained releases after disclosure on Python’s security-announce list and redistribution through the oss-security mailing list.
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3 events from the most recent confirmed update back to the earliest known activity.
Python disclosed CVE-2026-8328 as a medium-severity vulnerability affecting CPython's FTP passive mode handling in Lib/ftplib.py. The advisory explained that ftpcp() had bypassed the earlier CVE-2021-4189 PASV fix by directly calling parse227(), enabling SSRF via attacker-controlled PASV responses.
Python merged a patch on the main branch to make ftpcp() use the source server's actual peer address instead of trusting the server-supplied PASV IPv4 address, aligning behavior with FTP.makepasv(). The fix also preserved the existing trust_server_pasv_ipv4_address opt-out and was backported to multiple maintained branches.
Qi Ding (also identified as ikow, later attributed as being at Aurascape AI) reported a security issue in CPython's ftplib.ftpcp() function. The bug allowed a malicious source FTP server to supply a PASV host and port that could redirect a target server's data connection, creating an SSRF condition.
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CPython disclosed two medium-severity vulnerabilities affecting distinct parts of the runtime and tooling. **CVE-2026-1502** allows CR/LF bytes to pass through HTTP client proxy tunnel header or host handling, creating a header-injection risk in proxy tunnel scenarios. The issue was published through Python security channels and the `oss-sec` mailing list, with remediation details tracked in the CVE record and an associated CPython pull request. A second flaw, **CVE-2026-5713**, affects CPython remote debugging and introspection features and can trigger out-of-bounds read and write behavior when a privileged Python process connects to a malicious or compromised Python target. The bug impacts newer capabilities including `profiling.sampling` in Python 3.15+ and asyncio inspection commands such as ``` python -m asyncio ps python -m asyncio pstree ``` in Python 3.14+, and exploitation is expected to be unstable because the connecting process is likely to crash under ASLR.
Jun 29, 2026
Python disclosed **CVE-2026-15308**, a high-severity denial-of-service flaw in `html.parser.HTMLParser` that can drive CPU exhaustion when applications incrementally parse untrusted HTML containing repeated unterminated markup declarations. The bug stems from quadratic-time behavior in `feed()`, where small repeated chunks force expensive rescanning and buffer concatenation across malformed tags, comments, doctypes, CDATA sections, processing instructions, and RAWTEXT elements. CPython maintainers shipped fixes and backports across supported branches including 3.10 through 3.15, with commits updating buffering logic to accumulate pending input more efficiently, defer reparsing until enough data arrives, adapt parsing thresholds based on parser progress, and flush buffered data on `close()`. The Python Software Foundation also updated the CVE record to clarify that affected versions are **earlier than 3.15.0**, not earlier than 3.16.0, while published metadata classifies the issue as **CWE-400** and notes no known exploitation at the time of disclosure.
Jul 10, 2026
The Python Software Foundation disclosed a **critical authentication bypass** in the `python.org` release management API that could have let attackers forge administrator-level requests and modify Python release metadata. The flaw, reported by Splitline Ng of DEVCORE and confirmed by the Python Security Response Team, could have enabled changes to download and verification URLs for official Python installers, creating a path to distribute tampered files through trusted `python.org` infrastructure. The vulnerable logic reportedly dated back to 2014, affecting the release pipeline for more than a decade, but maintainers said post-incident forensics found **no evidence of exploitation**. The PSF patched the issue rapidly, with production fixes deployed within 24 hours and broader remediation completed within 48 hours, while also disabling risky API behavior and tightening release controls. Additional hardening included stricter URL validation, mandatory HTTPS enforcement, negative authentication test coverage, longer log retention, and stronger provenance measures around release artifacts, including emphasis on **Sigstore** alongside existing **PGP** signing. A subsequent Trail of Bits review funded by OpenAI reportedly found no additional authentication or authorization flaws, and the Foundation said the changes were designed to reduce the risk of unauthorized modification of Python downloads distributed via official channels.
Jul 12, 2026