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Infinite loop DoS in Python tarfile streaming mode

IdentifiersCVE-2026-11972CWE-835

CVE-2026-11972 is a high-severity denial-of-service vulnerability in CPython's tarfile module. When parsing a tar archive in streaming mode using mode="r|", the module does not properly handle end-of-file conditions. A crafted archive can trigger pathological parsing behavior, causing archive processing to take exponentially longer or enter an infinite loop. The issue is specific to tarfile usage in streaming mode and affects applications that accept and parse attacker-controlled tar archives with this mode enabled.

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation can cause the affected Python process to hang or consume excessive CPU while parsing a crafted tar archive. This results in denial of service against applications or services that process untrusted tar files in tarfile streaming mode. Based on the provided content, the issue is remotely exploitable where an attacker can supply a malicious archive to a vulnerable service.

Mitigation

If you can’t patch tonight, do this now.

Avoid using tarfile streaming mode (mode="r|") for untrusted archives where feasible until patched versions are deployed. Review code paths that parse attacker-supplied tar archives and prefer non-streaming handling or additional safeguards such as strict processing timeouts, CPU/resource limits, and isolation for archive-processing workers to reduce denial-of-service exposure.

Remediation

Patch, then assume compromise.

Upgrade CPython to a vendor-fixed release from the Python Software Foundation that includes the tarfile EOF-handling correction for CVE-2026-11972. Review all applications and services that use the tarfile module in streaming mode and update those runtimes to patched versions as they become available.
PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType
PythonCpythonapplication
PythonPythonapplication

Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.

ACTIVITY FEED

Recent activity

6 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.

6 SOURCESView more in app
What this page doesn’t show

The version that knows your environment.

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Exposure mapping

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Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity4

Community discussion across Reddit, Mastodon, and other social sources.

EXTERNAL REFERENCES
MITRE CVE
cve.org · CVE-2026-11972
NVD
nvd.nist.gov/vuln/detail/CVE-2026-11972
MITRE CWE · CWE-835
cwe.mitre.org