What’s Vulnerable › Vulnerabilities

CVE-2026-115274: Unbounded integer parsing in JSON.decode/1 enables CPU and memory exhaustion denial of service in Elixir

• Severity: medium (CVSS 6.9 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-30 · updated 2026-10-30
• Weakness: CWE-1284

Description

Improper Validation of Specified Quantity in Input vulnerability in the Elixir standard library's JSON module allows an unauthenticated attacker who supplies a JSON document to cause a denial of service through CPU and memory exhaustion. JSON.decode/1 and JSON.decode!/1 convert each integer literal with erlang:binary_to_integer/1 and do not bound its length. A literal of one million digits decodes successfully but costs 100 to 300 times as much CPU as a string of the same length, so one request body of a few megabytes holds a scheduler for about a second. A literal of more than about 1.29 million digits raises SystemLimitError. Applications generated by phx.new decode request bodies with JSON in Plug.Parsers, before routing and authentication. This issue affects elixir: from 1.18.0-rc.0 before 1.18.6, from 1.19.0-rc.0 before 1.19.7, and from 1.20.0-rc.0 before 1.20.5.

Affected products

• elixir-lang elixir: from 1.18.0-rc.0 before 1.18.6; from 1.19.0-rc.0 before 1.19.7; from 1.20.0-rc.0 before 1.20.5 — fixed in 1.18.6, 1.19.7, 1.20.5

How to fix

Upgrade to a fixed version: elixir-lang elixir 1.18.6, 1.19.7, 1.20.5. Check the vendor advisory for mitigations.

References

• https://cna.erlef.org/cves/CVE-2026-115274.html
• https://github.com/elixir-lang/elixir/commit/7154e8781da9fd016a973ea01776a011c8b5726a
• https://github.com/elixir-lang/elixir/commit/793c1147210388587defb649f25f293ffbfa6b1b
• https://github.com/elixir-lang/elixir/commit/c81f12265919c34a0d5134f1905a4eb4edaea1c2
• https://github.com/elixir-lang/elixir/commit/cd158efacdc10b30232864251747dff9b8387dfe
• https://github.com/elixir-lang/elixir/commit/ee5cc23f8928aa5a0f25bb7f28e42ecfc7b7d396
• https://github.com/elixir-lang/elixir/security/advisories/GHSA-rp5q-xqhq-926h
• https://osv.dev/vulnerability/EEF-CVE-2026-115274
• https://github.com/elixir-lang/elixir/security/advisories/GHSA-rp5q-xqhq-926h

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