CVE-2026-32288: Unbounded allocation for old GNU sparse in archive/tar

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-04-08 · updated 2026-07-25
Weakness: CWE-770

Description

tar.Reader can allocate an unbounded amount of memory when reading a maliciously-crafted archive containing a large number of sparse regions encoded in the "old GNU sparse map" format.

Affected products

Go: before 1.25.9; from 1.26.0 before 1.26.2 — fixed in 1.25.9, 1.26.2
Go Stdlib: before 1.25.9; from 1.26.0-0 before 1.26.2 — fixed in 1.25.9, 1.26.2

How to fix

Upgrade to a fixed version: Go 1.25.9, 1.26.2; Go Stdlib 1.25.9, 1.26.2. Check the vendor advisory for mitigations.

References

https://go.dev/cl/763766
https://go.dev/issue/78301
https://groups.google.com/g/golang-announce/c/0uYbvbPZRWU
https://pkg.go.dev/vuln/GO-2026-4869

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