Unbounded exponent in decimal enables unauthenticated DoS

Weakness Type (CWE)

CWE-400 — CWE-400 Uncontrolled Resource Consumption

CAPEC

CAPEC-130 — CAPEC-130 Excessive Allocation

CVSS 4.0 Score

6.9

MEDIUM

CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Vulnerability description

Uncontrolled Resource Consumption vulnerability in ericmj decimal allows unauthenticated remote Denial of Service.

The decimal library does not bound the exponent on parsed input. Storing a decimal with a very large exponent (e.g. Decimal.new("1e1000000000")) is accepted without error. Subsequent calls to arithmetic functions (Decimal.add/2, Decimal.sub/2, Decimal.div/2), Decimal.to_string/2 with :normal or :xsd format, Decimal.to_integer/1, Decimal.round/3, or Decimal.compare/3 with a threshold allocate memory proportional to the exponent value, which can exhaust available memory and crash the BEAM VM.

Any application that accepts user-supplied decimal input and subsequently performs arithmetic, rounding, conversion to integer, or string formatting on it is exposed. A single malicious request is sufficient to cause an out-of-memory crash.

This issue affects decimal: from 0.1.0 before 3.0.0.

Affected

`pkg:hex/decimal`

Module	Source File	Routine
`Decimal`	`lib/decimal.ex`	`Decimal.new/1`
		`Decimal.parse/1`
		`Decimal.cast/1`
		`Decimal.add/2`
		`Decimal.sub/2`
		`Decimal.div/2`
		`Decimal.to_string/2`
		`Decimal.to_integer/1`
		`Decimal.round/3`
		`Decimal.compare/3`

Status	Type	Version	Changes / Fixed in
affected	semver ^ⓘ	`0.1.0`	< `3.0.0`

`pkg:github/ericmj/decimal`

Module	Source File	Routine
`Decimal`	`lib/decimal.ex`	`Decimal.new/1`
		`Decimal.parse/1`
		`Decimal.cast/1`
		`Decimal.add/2`
		`Decimal.sub/2`
		`Decimal.div/2`
		`Decimal.to_string/2`
		`Decimal.to_integer/1`
		`Decimal.round/3`
		`Decimal.compare/3`

Status	Type	Version	Changes / Fixed in
affected	git ^ⓘ	`bc11f4a2b6`	< `6a523f3a73`

References

https://github.com/ericmj/decimal/security/advisories/GHSA-rhv4-8758-jx7v vendor-advisory related
https://osv.dev/vulnerability/EEF-CVE-2026-32686 related
https://github.com/ericmj/decimal/commit/6a523f3a73b8c9974540e21c7aa88f1258bb35ae patch

Credits

Finder: Peter Ullrich
Remediation developer: Eric Meadows-Jönsson
Remediation reviewer: José Valim
Remediation reviewer: Wojtek Mach
Analyst: Jonatan Männchen
Remediation reviewer: ruslandoga
Remediation reviewer: Matthew Johnston

CVE record as JSON: GET /cves/CVE-2026-32686.json
OSV record as JSON: GET /osv/EEF-CVE-2026-32686.json