mppx: Gas Draining with padding
cve-program · CVE-2026-63627
Publishedmppx is a TypeScript interface for machine payments protocol. Prior to 0.8.2, FeePayerPolicy in src/tempo/internal/fee-payer.ts used decodeFunctionData to validate fee-sponsored calldata but did not reject trailing bytes. A client could append nonzero padding that increased intrinsic calldata gas while gas_limit and max_fee_per_gas remained within policy caps, causing the server fee_payer wallet to pay substantially more than the decoded transaction required. The tested 16 KB header limit bounded the demonstrated padding to about 5,500 bytes and produced approximately five times the normal transaction fee. This issue is fixed in version 0.8.2.
Read the publisher's advisoryeuvd · EUVD-2026-84805
Publishedmppx is a TypeScript interface for machine payments protocol. Prior to 0.8.2, FeePayerPolicy in src/tempo/internal/fee-payer.ts used decodeFunctionData to validate fee-sponsored calldata but did not reject trailing bytes. A client could append nonzero padding that increased intrinsic calldata gas while gas_limit and max_fee_per_gas remained within policy caps, causing the server fee_payer wallet to pay substantially more than the decoded transaction required. The tested 16 KB header limit bounded the demonstrated padding to about 5,500 bytes and produced approximately five times the normal transaction fee. This issue is fixed in version 0.8.2.
Read the publisher's advisorynvd · CVE-2026-63627
Publishedmppx is a TypeScript interface for machine payments protocol. Prior to 0.8.2, FeePayerPolicy in src/tempo/internal/fee-payer.ts used decodeFunctionData to validate fee-sponsored calldata but did not reject trailing bytes. A client could append nonzero padding that increased intrinsic calldata gas while gas_limit and max_fee_per_gas remained within policy caps, causing the server fee_payer wallet to pay substantially more than the decoded transaction required. The tested 16 KB header limit bounded the demonstrated padding to about 5,500 bytes and produced approximately five times the normal transaction fee. This issue is fixed in version 0.8.2.
Read the publisher's advisoryosv · GHSA-727h-3vm5-qwq6
Published### Details When the server acts as the fee_payer, `mppx` 0.6.27 validates calldata using viem's `decodeFunctionData`, which is lenient about trailing bytes. The `FeePayerPolicy` caps `gas_limit` (≤ 2 M) and `max_fee_per_gas` (≤ 100 Gwei) but does **not** check calldata length. Tempo uses legacy calldata gas pricing: **16 gas per non-zero byte**. Appending `N` bytes of `0x01` padding inflates actual gas used by `N × 16` while keeping `gas_limit` and `max_fee_per_gas` within policy caps. The server cosigns and broadcasts the padded transaction, draining its fee-payer wallet. **Vulnerable code path:** `FeePayerPolicy` in `fee-payer.ts` (mppx 0.6.27) enforces `maxGas = 2_000_000` and `maxFeePerGas = 100 Gwei` but has no `calldata.length` bound. The policy check passes because the inflated gas comes from intrinsic calldata cost, not the declared `gas_limit`. **Note:** In the experiment, a 16 KB `max_header_length` is enforced, which caps the maximum effective padding at roughly 5,500 bytes. The default padding in this PoC (5,500 bytes) is within that limit. ### PoC The PoC is provided below. It is configured to reproduce the attack on Tempo Moderate testnet within a Docker environment. Download the PoC and run: ```bash unzip mppx_typescript_PoC.zip cd mppx_typescript docker build -t mppx-padding . docker run --rm mppx-padding ``` There are more details in `mppx_typescript/README.md` ### Impact A malicious client can force the server to pay ~**5x** the normal transaction fee. This dramatically increases operational costs and completely destroys the profit margin on low-cost items. Please provide a way to share the PoC in .zip format to you. Thank you!
Read the publisher's advisoryAffected versions, risk and source history
Exploitation and risk
Source statusCISA KEV lists vulnerabilities known to be exploited. FIRST EPSS estimates the likelihood of exploitation in the next 30 days. An unavailable score does not mean zero risk.
Which CVEs have scores here?
This view includes predictions for CVE identifiers explicitly listed in public NuGet advisories. Microsoft release pages have their own prediction coverage. Check source status for the scope and latest checks.
No exploitation or prediction data is available here for these CVEs. This does not mean they are safe or unlikely to be exploited.
cve-program · CVE-2026-63627
Publishedmppx: Gas Draining with padding
mppx is a TypeScript interface for machine payments protocol. Prior to 0.8.2, FeePayerPolicy in src/tempo/internal/fee-payer.ts used decodeFunctionData to validate fee-sponsored calldata but did not reject trailing bytes. A client could append nonzero padding that increased intrinsic calldata gas while gas_limit and max_fee_per_gas remained within policy caps, causing the server fee_payer wallet to pay substantially more than the decoded transaction required. The tested 16 KB header limit bounded the demonstrated padding to about 5,500 bytes and produced approximately five times the normal transaction fee. This issue is fixed in version 0.8.2.
- Source published
- 22 Sep 2026 19:07:02 UTC
- Source modified
- 23 Sep 2026 14:36:37 UTC
- Saved here
- 23 Oct 2026 15:48:27 UTC
- Source terms
- CVE Program Terms of Use
Original source record · Cite this exact observation · Complete original publisher JSON
Source: cve-program · CVE Program Terms of Use. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.
CVSS 4.0 · 6.9 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
euvd · EUVD-2026-84805
Publishedmppx is a TypeScript interface for machine payments protocol. Prior to 0.8.2, FeePayerPolicy in src/tempo/internal/fee-payer.ts used decodeFunctionData to validate fee-sponsored calldata but did not reject trailing bytes. A client could app…
mppx is a TypeScript interface for machine payments protocol. Prior to 0.8.2, FeePayerPolicy in src/tempo/internal/fee-payer.ts used decodeFunctionData to validate fee-sponsored calldata but did not reject trailing bytes. A client could append nonzero padding that increased intrinsic calldata gas while gas_limit and max_fee_per_gas remained within policy caps, causing the server fee_payer wallet to pay substantially more than the decoded transaction required. The tested 16 KB header limit bounded the demonstrated padding to about 5,500 bytes and produced approximately five times the normal transaction fee. This issue is fixed in version 0.8.2.
Additional publisher context
EUVD source date text has no stated timezone and is retained without inventing a UTC instant. Related bulletin membership is not an alias, common cause or applicability claim. A missing vector with a zero score is treated as unrated. Complete vendor/product and underlying source evidence remains in the original JSON.
Original publisher date fields
datePublished: Sep 22, 2026, 7:07:02 PM
dateUpdated: Sep 23, 2026, 2:36:37 PM
- Source published
- Sep 22, 2026, 7:07:02 PM (timezone not stated)
- Source modified
- Sep 23, 2026, 2:36:37 PM (timezone not stated)
- Saved here
- 11 Nov 2026 15:06:38 UTC
- Source terms
- ENISA EUVD · source terms and attribution apply
Original source record · Cite this exact observation · Complete original publisher JSON
Source: euvd · ENISA EUVD · source terms and attribution apply. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.
EUVD CVSS 4.0 · 6.9 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
nvd · CVE-2026-63627
Publishedmppx is a TypeScript interface for machine payments protocol. Prior to 0.8.2, FeePayerPolicy in src/tempo/internal/fee-payer.ts used decodeFunctionData to validate fee-sponsored calldata but did not reject trailing bytes. A client could app…
mppx is a TypeScript interface for machine payments protocol. Prior to 0.8.2, FeePayerPolicy in src/tempo/internal/fee-payer.ts used decodeFunctionData to validate fee-sponsored calldata but did not reject trailing bytes. A client could append nonzero padding that increased intrinsic calldata gas while gas_limit and max_fee_per_gas remained within policy caps, causing the server fee_payer wallet to pay substantially more than the decoded transaction required. The tested 16 KB header limit bounded the demonstrated padding to about 5,500 bytes and produced approximately five times the normal transaction fee. This issue is fixed in version 0.8.2.
Additional publisher context
NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON.
Source analysis status: Awaiting Analysis
Weakness classifications: CWE-20
Original publisher date fields
published: 2026-09-22T20:17:04.763
lastModified: 2026-09-23T18:12:04.247
- Source published
- 22 Sep 2026 20:17:04 UTC
- Source modified
- 23 Sep 2026 18:12:04 UTC
- Saved here
- 25 Oct 2026 15:18:45 UTC
- Source terms
- NIST NVD usage terms; underlying source attribution retained
Original source record · Cite this exact observation · Complete original publisher JSON
Source: nvd · NIST NVD usage terms; underlying source attribution retained. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.
CVSS 4.0 · [email protected] · Secondary · 6.9 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/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
osv · GHSA-727h-3vm5-qwq6
Publishedmppx: Gas Draining with padding
### Details When the server acts as the fee_payer, `mppx` 0.6.27 validates calldata using viem's `decodeFunctionData`, which is lenient about trailing bytes. The `FeePayerPolicy` caps `gas_limit` (≤ 2 M) and `max_fee_per_gas` (≤ 100 Gwei) but does **not** check calldata length. Tempo uses legacy calldata gas pricing: **16 gas per non-zero byte**. Appending `N` bytes of `0x01` padding inflates actual gas used by `N × 16` while keeping `gas_limit` and `max_fee_per_gas` within policy caps. The server cosigns and broadcasts the padded transaction, draining its fee-payer wallet. **Vulnerable code path:** `FeePayerPolicy` in `fee-payer.ts` (mppx 0.6.27) enforces `maxGas = 2_000_000` and `maxFeePerGas = 100 Gwei` but has no `calldata.length` bound. The policy check passes because the inflated gas comes from intrinsic calldata cost, not the declared `gas_limit`. **Note:** In the experiment, a 16 KB `max_header_length` is enforced, which caps the maximum effective padding at roughly 5,500 bytes. The default padding in this PoC (5,500 bytes) is within that limit. ### PoC The PoC is provided below. It is configured to reproduce the attack on Tempo Moderate testnet within a Docker environment. Download the PoC and run: ```bash unzip mppx_typescript_PoC.zip cd mppx_typescript docker build -t mppx-padding . docker run --rm mppx-padding ``` There are more details in `mppx_typescript/README.md` ### Impact A malicious client can force the server to pay ~**5x** the normal transaction fee. This dramatically increases operational costs and completely destroys the profit margin on low-cost items. Please provide a way to share the PoC in .zip format to you. Thank you!
- Source published
- 22 Sep 2026 20:34:17 UTC
- Source modified
- 22 Sep 2026 21:00:04 UTC
- Saved here
- 24 Oct 2026 13:17:17 UTC
- Source terms
- GitHub Advisory Database · CC-BY-4.0
Original source record · Cite this exact observation · Complete original publisher JSON
Source: osv · GitHub Advisory Database · CC-BY-4.0. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.
CVSS_V4 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
Publisher rating · MODERATE