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CVE-2026-113603

MEDIUMCVSS 6.5/10EPSS 0.29%

Last modified

CVE-2026-113603 is a medium-severity vulnerability rated 6.5/10 on the CVSS scale. The x402 SIWX server extension in @x402/extensions 2.3.1 through 2.28.0, x402 PyPI 2.11.0 through 2.25.0, and Go module 2.16.0 through 2.28.0 contains an authorization bypass vulnerability that allows paying clients to unlock unpaid routes by supplying a mismatched PaymentPayload.resource URL. Attackers can pay for the cheapest SIWX-protected route while setting resource.url to an expensive route, then repeatedly access it using only a SIGN-IN-WITH-X header without further payment.. EPSS estimates a 0.29% chance of exploitation in the next 30 days.

Description

The x402 SIWX server extension in @x402/extensions 2.3.1 through 2.28.0, x402 PyPI 2.11.0 through 2.25.0, and Go module 2.16.0 through 2.28.0 contains an authorization bypass vulnerability that allows paying clients to unlock unpaid routes by supplying a mismatched PaymentPayload.resource URL. Attackers can pay for the cheapest SIWX-protected route while setting resource.url to an expensive route, then repeatedly access it using only a SIGN-IN-WITH-X header without further payment.

Metrics

CVSS 3.1
6.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

CVSS 4.0
6.9/10

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS Probability
0.29%

20.5th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

VendorProductVersions
x402-foundation@x402/extensions>= 2.3.1, <= 2.28.0
x402-foundationx402>= 2.11.0, <= 2.25.0
x402-foundationgithub.com/x402-foundation/x402/go/v2>= 2.16.0, <= 2.28.0

References

Timeline

Published
Last Modified
Status
Awaiting Analysis

Frequently Asked Questions

What is CVE-2026-113603?
The x402 SIWX server extension in @x402/extensions 2.3.1 through 2.28.0, x402 PyPI 2.11.0 through 2.25.0, and Go module 2.16.0 through 2.28.0 contains an authorization bypass vulnerability that allows paying clients to unlock unpaid routes by supplying a mismatched PaymentPayload.resource URL. Attackers can pay for the cheapest SIWX-protected route while setting resource.url to an expensive route, then repeatedly access it using only a SIGN-IN-WITH-X header without further payment.
How severe is CVE-2026-113603?
CVE-2026-113603 has a CVSS score of 6.5/10 (MEDIUM severity). The EPSS model estimates a 0.29% probability of exploitation in the next 30 days.
How do I fix CVE-2026-113603?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST