CVE-2026-87910 — tarfile hardlink fallback ignores custom extraction filter rejection via None

When tarfile extracts a link on a system that doesn't support links, it falls back to extracting a member from the archive. In this case, the filter function is run twice: once for the extracted member, and once with name set to the location of the link. For one of the calls, the return value was ignored. Instead, the member should be skipped if either call returns None.

Published Sep 11, 2026Updated Oct 1, 2026Sources: cvelistV5, PSF

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the scoring sources call it.

Exploitation

Unreported

no source claims exploitation

EPSS

chance of exploitation in 30 days

Affects

python software foundation

cpython

CVSS base

5.7

MEDIUM

CISA SSVC assessment

Three decision points CISA publishes for the CVEs it assesses · SSVC 2.0.3. A stakeholder decision, not a severity score.

CISA

Exploitation

None

none · proof-of-concept · active

Automatable

can an attacker script all four kill-chain steps

Technical impact

Partial

partial · total control of the vulnerable component

Affected scope

The catalog records vendors and products as separate lists, not pairs, so which product belongs to which vendor is not something this page can say.

Vendors (1)

python software foundation

Products (1)

cpython

Every base score collected

Sources score independently and disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Source
5.7	CVSS 4.0	MEDIUM	—	—	cvelistV5

Weakness & attack patterns

CWE-22
CWE-59

Attack patterns reported against this CVE. The ATT&CK techniques below are inferred from its weakness class.

T1547.009Boot or Logon Autostart Execution: Shortcut Modification
T1574.005Hijack Execution Flow: Executable Installer File Permissions Weakness
T1574.010Hijack Execution Flow: Services File Permissions Weakness

References

10 on the record

Elsewhere on this site

python software foundationevery CVE for this vendor
CWE-22other pages naming this weakness

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.